semester, 2017

Monday, January 2nd 2017

Monday, January 16th 2017
12:15 pm:
There will be no seminar this week.

Tuesday, January 17th 2017
09:30 am:
Organizational Meeting

Wednesday, January 18th 2017
1:25 pm:
Speaker: Aliaksei Charnukha, University of California, San Diego
Subject: Charge dynamics in iron-based superconductors
Candidate for the Condensed Matter Experimental Assistant Professor Position

More than a century after the discovery of dissipationless charge transport in mercury below 4.2K, the search for room-temperature superconductivity continues. Record-high transition temperatures above 200K have been achieved but only under the extreme conditions of ultra-high pressure or, possibly, intense transient light fields. The leading candidate for realizing ambient superconductivity have remained strong electronic correlations, an established ingredient in unconventional high-temperature copper-based superconductivity. Iron-based compounds have emerged as entirely distinct species, in which superconductivity can be refined to a single atomic layer and enhanced to occur at 65K by interfacial interactions. Here, we will consider the influence of many-body effects on the low-energy charge transport and band structure in iron-based superconductors and parent compounds in order to shed light onto the microscopic mechanism of superconducting pairing in this novel class of materials.

Faculty Host: James Kakalios
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 120
There will be no journal club this week.

Thursday, January 19th 2017
11:15 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
3:35 pm:
There will be no colloquium this week.

Friday, January 20th 2017
11:15 am:
Organizational Meeting
There will be no seminar this week.
There will be no seminar this week.
No Colloquium
3:35 pm:
Speaker: Jed Elison, Institute of Child Development - University of Minnesota
Subject: "Considering Temporal Heterogeneity in Autism”
Refreshments served at 3:25 p.m.

The genetic and phenotypic heterogeneity integral to the phenomenon of autism is well characterized, yet recent evidence highlights a third source of variability that warrants careful consideration. Temporal heterogeneity, a term borrowed from ecological theory, considered in the context of psychiatric disorders, denotes observed variability in developmental timing as it relates to disease phenomena. Temporal heterogeneity may represent a specific feature of phenotypic heterogeneity or capture evolving patterns of environmental demands that temporally coincide with changes in the developing organism. And yet, simply entertaining the concept challenges traditional notions of diagnostic stability and issues related to nosology.

There will be no seminar this week.
4:40 pm:
To be announced.

Monday, January 23rd 2017
12:15 pm:
Speaker: Lauren Pearce, University of Minnesota
Subject: Phenomenology of Trapped Inflation

While there is good support for the inflationary paradigm, evidence does not clearly point to any particular inflationary model. Therefore, it is imperative that careful calculations are done to allow cosmological observations to constrain models. In this talk, we will look at cosmological constraints on trapped inflation, amodel in which the inflaton undergoes slow roll because it is losing energy to particle production, not because of the flatness of its potential.

Tuesday, January 24th 2017
12:20 pm:
Speaker: James Mason, University of Colorado
Subject: The Success and the Science of the Student-Built MinXSS Solar CubeSat

CU Boulder and LASP have a long history of involving students in every aspect of science spacecraft production. The most recent incarnation is the Miniature X-ray Solar Spectrometer (MinXSS) CubeSat, which was sent to the International Space Station with resupply cargo and then deployed from the airlock on 2016 May 16. Students were heavily involved in the design, manufacturing, assembly, extensive testing, delivery to Houston; and continue to be involved in the mission operations, data pipeline production, and science analysis. CubeSats are comparatively low cost for spacecraft and as such the programs tend to accept more risk, the result of which is a higher rate of failure. The ongoing MinXSS-1 mission has exceeded comprehensive success criteria, has been featured by NASA, won the 2016 AIAA SmallSat mission of the year award, and is the first science CubeSat funded by NASA to be launched. I’ll touch on how we made sure MinXSS would be a success. I’ll also describe some of the early science results from the MinXSS-1 mission, which focus on the energetic processes that occur in the solar corona. Finally, I’ll discuss what we wish we would have done on MinXSS-1; fortunately, we built two satellites so we can make those wishes a reality on MinXSS-2, scheduled to launch in the first half of 2017.

Wednesday, January 25th 2017
1:25 pm:
Speaker: Arnab Banerjee, ORNL - Oak Ridge National Laboratory
Subject:  In search of Majorana Fermions in a honeycomb semiconductor
Candidate for the Condensed Matter Experimental Assistant Professor Position

In a normal magnet strong interactions tend to align the spins in a periodic fashion forming a ferromagnet or an antiferromagnet. However, sometimes when the interactions compete with each other, the spins cannot order into a single low-energy ground state and keep on fluctuating, resulting in highly degenerate ground states with very interesting emergent quantum behavior. Such a ground state is the Kitaev quantum spin liquid (KQSL) which occurs in a honeycomb semiconductor and predicts the emergence of Majorana Fermions and non-abelian anyons that can be used for topological quantum computation. It was proposed that certain d5 materials with a strong octahedral crystal field and a strong spin-orbit coupling in a low-spin ground state can realize a KQSL. In this talk, I will describe the synthesis, ground-state properties and the excitation spectrum of a graphene-like honeycomb magnet a-RuCl3 which complies with the requirements. Using neutron scattering we show that, despite a low-temperature long-range order, the excitation spectrum contains an unusual broad feature matching the predictions of Majorana Fermions arising from strong Kitaev interactions. Detailed theoretical analysis allows us to compare our spectrum with Kitaev exact solutions as well as extensions based on mean-field approximations. Finally, we will talk about our recent endeavors to extend this work using doping, thin-films and application of magnetic field. The later, most interestingly, suppresses the long-range order hopefully leading to a true spin-liquid state.

Faculty Host: James Kakalios

Thursday, January 26th 2017
11:15 am:
Biophysics Seminar in 120 PAN
To be announced.
12:05 pm:
Speaker: Melanie Beck and Terry Jones
3:35 pm:
Speaker: Mary K. Gaillard, University of California, Berkeley
Subject:  A Singularly Unfeminine Profession
Refreshments to be served outside Smith 100 after the colloquium.

I will recount some of my experiences as a woman in a very male dominated field, while tracing the development of the Standard Model as I witnessed it and participated in it.

Faculty Host: Tony Gherghetta

Friday, January 27th 2017
11:15 am:
Subject: To be announced
Speaker: Qianhui Shi, University of Minnesota
Subject: The orientation of quantum Hall stripes
Speaker: Yi-Zen Chu (U. Minnesota-Duluth)
Subject: Cosmological Gravitational Waves: Causal Structure And Memories

Despite being associated with particles of zero rest mass, electromagnetic and gravitational waves do not travel solely on the null cone in generic curved spacetimes. (That is, light does not always propagate on the light cone.) This inside-the-null-cone propagation of waves is known as the tail effect, and finding novel ways of understanding it in the strong field regime near a black hole may find applications for modeling the gravitational signals sought after by next-generation space-based detectors such as LISA

Speaker: Sanchayeeta Borthakur, Johns Hopkins, Dept. of Physics & Astronomy
Subject: Role of Baryon Flows in Galaxy Evolution: Hidden Pathways Connecting Galaxies to the Cosmic Web
Candidate for the MIfA Assistant Professor position

Galaxies are not isolated. They constantly exchange matter and energy with their surroundings. In spite of these pathways being obscure, they have had immense consequences. For example, galaxy growth and subsequent star formation is maintained by gradual accretion of gas from the cosmic web. In turn, young stars produce vast amounts of energy that may ionize gas in the cosmic web as well as spew out metals in the intergalactic medium (IGM). I will talk about the advances we have made in understanding the physics behind these pathways via studies of the circumgalactic medium (CGM). It is the vast reservoir of faint tenuous gas that extends from the edge of the disks of galaxies out to their virial radii. Therefore, the CGM holds crucial keys to understanding the various inflow and outflow processes. I will discuss observations of the CGM that suggests of these pathways via which galaxies acquire gas, condense it into their interstellar medium, form stars, and finally, release matter and energy back into their CGM and the IGM.

3:35 pm:
Speaker: Abigail Neely, Department of Geography - Dartmouth College
Subject:  “Entangled Agencies: Reimagining Social Medicine from Pholela”
Refreshments served at 3:25 p.m.

In this talk, I examine a world famous experiment in social medicine -- the Pholela Community Health Centre -- through the lives and health of the African residents of Pholela, South Africa, where it was implemented. In particular, I use residents' experiences with witchcraft to examine the limitations of the social medicine practiced there. Using a relational ontology, I argue that the Pholela Community Health Centre's social medicine was limited by the ways health care professionals understood the social and the biological factors that affect health.

Speaker: Jos Uffink, University of Minnesota

Monday, January 30th 2017
12:15 pm:
Speaker: Burcin Mutlu-Pakdil, UMN
Subject: Discovery of an extremely rare galaxy: PGC 1000714

Non-barred ringed galaxies are among the ideal galaxies to study the role of both the internal dynamics of galaxies and the physics of accretion/interaction mechanisms. An especially interesting ring case is Hoag's Object with its peculiar morphology: an elliptical-like core with a nearly perfect outer ring, and no signs of bar and stellar disc. Hoag-type galaxies, which bear strong resemblance to Hoag's Object, are extremely rare and their origin is still debated. Our recent work has revealed a unique case for Hoag-type galaxies: PGC 1000714 presents strong resemblance to Hoag's Object in the optical and near-ultraviolet bands,with an additional structure — a second inner ring, which is more diffuse, and redder than the outer ring. Such peculiar systems help our understanding of galaxy formation in general, since they represent extreme cases, providing clues on formation mechanisms.

In the first part of my talk, I will simply overview the concept of ringed galaxies and introduce Hoag-type galaxies. Then, I will present my work on PGC 1000714 and finally conclude with a discussion about the implications of our findings.

Tuesday, January 31st 2017
12:20 pm:
Speaker: Sophie Musset, University of Minnesota
Subject: Energetic electrons acceleration and transport in the corona (via X-ray diagnostics): from RHESSI data analysis to the preparation of the STIX experiment on Solar Orbiter.

An important fraction of the magnetic energy released during solar flares is transmitted to ambient particles which can be accelerated to energies of several hundreds of keV to a few keV for electrons, and several tens to a few hundreds of MeV for ions. Yet, we only poorly know the details of the physical mechanisms responsible for fast and efficient particle acceleration, and for the transport of energetic particle between acceleration sites and interaction sites where they emit electromagnetic radiation. I will present the work conducted during my PhD preparation at the Observatoire de Paris, in the context of the study of solar energetic electron acceleration and transport in the solar corona through X-ray diagnostics.

In the first part of the seminar, I will present how I investigated the link between energetic electron X-ray emissions and electric current densities measured at the photospheric level during X-class solar flares. This work shows that energetic electron acceleration sites are located above the highest current densities for several X-class flares. A common evolution of X-ray emission and photospheric electric currents has also been shown during a flare (Musset et al 2015). In a second study, I examined the effect of transport in the corona on the energetic electron distribution during a flare. A fraction of energetic electrons are trapped in the coronal part of the flare loop, and it can be explained with a diffusive transport model. Combining X-ray and radio observations, the scattering mean free path was estimated at different electrons energies for the first time in the solar corona, and shown to be decreasing with increasing energy.

In the second part of the seminar, I will present the STIX instrument onboard Solar Orbiter, which will provide X-ray diagnostics of the sources of energetic electrons in the solar corona. I will briefly present the challenges and some of the advances made in term of onboard and analysis software for this experiment.

4:30 pm:
There will be no seminar this week.

Wednesday, February 1st 2017
1:25 pm:
Speaker: Ben Feldman, Princeton University
Subject: Real-space imaging of a nematic quantum liquid
Candidate for the Condensed Matter Experimental Assistant Professor Position

The wave functions of electronic states in solids typically respect the symmetries of the host material. However, interactions among electrons can give rise to a variety of exotic correlated phases characterized by broken symmetry. An intriguing example is the formation of electron fluids with wave functions that spontaneously break the symmetry of the underlying crystal lattice. These phases are quantum analogues of classical liquid crystals and have been studied in recent years across disparate platforms ranging from high-temperature superconductors to two-dimensional electron systems. In this talk, I will describe scanning tunneling microscope measurements that allow us to visualize such a quantum liquid in real space. We examine the quantum Hall states that arise at high magnetic field from anisotropic Fermi pockets on the surface of bismuth. Our measurements reveal that a combination of strain and exchange interactions lift the Landau level degeneracy and produce valley-polarized states. We image the resulting anisotropic wave functions and find that they have a different orientation for each broken-symmetry state, providing a direct spatial signature of a nematic electronic phase.

Faculty Host: James Kakalios
To be announced.
4:30 pm:
CM Journal Club in PAN 120
No JC this week.

Thursday, February 2nd 2017
11:15 am:
Biophysics Seminar in 120 PAN
Speaker: David Punihaole, University of Minnesota, Department of Chemistry
Subject: UV Resonance Raman Spectroscopy: A New Tool to Probe Amyloid-like Fibril Structures

There is currently little that is known about the structure of polyglutamine (polyQ) fibrils, which are involved in at least ten neurodegenerative diseases, including Huntington’s. Given their insoluble and non-crystalline nature, new and incisive biophysical methods need to be developed in order to obtain high-resolution structural information of polyQ and other amyloid-like fibrils. Here, we present our recent advances in UV resonance Raman (UVRR) spectroscopy that enable the elucidation of molecular-level structural information of amyloid-like fibrils. We show, for example, how the primary amide UVRR bands report on the local hydrogen bonding and dielectric environment of glutamine side chains. We also discuss a newly discovered spectroscopic marker, the Amide IIIP vibration, which sensitively reports on the side chain structure of glutamine. These and other spectroscopic markers are used to gain insights into the peptide backbone and side chain conformations of polyQ peptides in solution-state and in fibrils. Finally, we demonstrate how the structural information obtained from UVRR can be utilized to guide Molecular Dynamics simulations in order to obtain experimentally validated structural models of polyQ fibrils.

12:05 pm:
Speaker: Jonathan Fortney (UCSC)
3:35 pm:
Speaker: John Bowers, UCSB
Subject: Heterogeneous Photonic Integration on Silicon
Refreshments to be served outside Smith 100 after the colloquium.

We review recent advances in heterogeneous silicon photonic integration technology and components and describe progress in silicon photonic integrated circuits. Techniques for laser integration and the impact of active silicon photonic integrated circuits could have on interconnects, telecommunications and silicon electronics are reviewed. A variety of materials are being heterogeneously integrated, including arsenides for short wavelength lasers, phosphides for infrared lasers, LiNbO3 for nonlinear applications and YIG for isolators and circulators. One application that has been recently demonstrated is a 2.56 Tbit/s optical network on a chip that involved integrating over 400 optical elements, including DFB lasers, EAMs, photodetectors, and AWGs to make 64 transceivers operating at 40 Gbit/s.

John E. Bowers holds the Fred Kavli Chair in Nanotechnology, and is the Director of the Institute for Energy Efficiency and a Professor in the Departments of Materials and Electrical and Computer Engineering at UCSB. He is a cofounder of Aurrion, Aerius Photonics and Calient Networks. Dr. Bowers received his M.S. and Ph.D. degrees from Stanford University and worked for AT&T Bell Laboratories and Honeywell before joining UC Santa Barbara. Dr. Bowers is a member of the National Academy of Engineering and the National Academy of Inventors. He is a fellow of the IEEE, OSA and the American Physical Society, and a recipient of the IEEE Photonics Award, OSA Tyndal Award, the OSA Holonyak Prize, the IEEE LEOS William Streifer Award and the South Coast Business and Technology Entrepreneur of the Year Award. He has published eight book chapters, 600 journal papers, 900 conference papers and has received 54 patents. He and coworkers received the EE Times Annual Creativity in Electronics (ACE) Award for Most Promising Technology for the hybrid silicon laser in 2007.

Faculty Host: Marvin Marshak

Friday, February 3rd 2017
Speaker: Zach Anderson, University of Minnesota
Subject: Antiferromagnetic excitations in Mercury Barium Copper Oxide
Speaker: Mikhail Goykhman (U Chicago)
Subject: Large-N three-dimensional matter and Landau Fermi liquid

One of the typical low-temperature phases of fermionic matter is
described by a phenomenological theory called Landau Fermi liquid.
I will be discussing the first proposed exactly solvable
microscopic theories which behave at low energies as Landau Fermi liquid.
These theories are the large-N three-dimensional Chern-Simons-fermion
and Thirring models. I will demonstrate how the three-dimensional
large-N power allows one to obtain exact results, at any value of the coupling
constant, for a number of interesting observables.

2:00 pm:
Speaker: Jurgen Eser, Frankfurt Institute for Advanced Studies
Subject: The extended linear sigma model within the functional renormalization group approach
Note change in time and location, this week only.

by Jurgen Eser, Florian Divotgey, Dirk H. Rischke

We use the functional renormalization group (FRG) technique to explore the characteristics of the so-called extended linear sigma model (eLSM). This model is an effective description of the strong interaction in terms of quarks and mesonic felds. Besides scalars and pseudoscalars, it also features vector and axial-vector mesons.

The first part focuses on the restoration of chiral symmetry in the context of the transition from hadronic matter to the quark-gluon plasma in the phase diagram of quantum chromodynamics (QCD). Results on the order of the chiral phase transition in the presence of vector and axial-vector mesons will be presented. Vector mesons are of particular interest since modifications related to chiral symmetry restoration affect their in-medium spectral properties, which can be detected via decays into dileptons. Effects of the axial anomaly and the explicit breaking of chiral symmetry due to nonzero quark masses are also studied. The mass degeneracy of chiral partners beyond the phase boundary and the phase diagram as a function of the temperature and the quark-chemical potential will be shown.

The second part sheds light on the low-energy limit of the eLSM. We consider the influence of wave-function renormalization factors and couplings beyond the local potential approximation. The infrared-relevant couplings can be associated with the corresponding low-energy constants of QCD.

Speaker: Brendan Bowler, University of Texas - Austin, Hubble Fellow
Subject: Revealing the Formation and Atmospheres of Exoplanets with Direct Imaging
Candidate for the MIfA Assistant Professor position

Finding and characterizing extrasolar planets has become one of the fastest-paced and most rapidly evolving fields in modern astronomy. Direct imaging— spatially resolving exoplanets from their host stars— is especially challenging but provides unique insight into the architectures, atmospheres, and formation of giant planets. By exploring planetary systems from the outside-in and directly detecting photons originating in their atmospheres, imaging complements other planet-finding techniques sensitive to smaller orbital separations and enables detailed studies of atmospheric structure and composition. In this talk I will review the field of high-contrast adaptive optics imaging with an emphasis on observational programs I am leading to test theories of planet formation, primarily by means of large surveys, planet population statistics, and near-infrared spectroscopy. I will also outline the long-term future of the field; imaging planets has been a consistent motivating factor for the next generation of telescopes like JWST, WFIRST, and the 30 meter-class telescopes. Eventually these facilities will pave the way for the ultimate objective: a dedicated space-based mission to image and characterize Earth analogs.

3:35 pm:
Speaker: Ed Larson, Pepperdine University
Subject: "Red Dawn Rising: the Sketchy History and Techno-thriller Prospects of Geoengineering"
Refreshments served at 3:25 p.m.

The global debate over the danger of human-caused climate change has spawned a secondary one over geoengineering as a possible human-instigated response with attention increasingly focusing on the intentional injection of sulfate aerosols into the stratosphere to cool the earth. Over the past two decades, this idea has moved from a crank concept supported by a few fringe technologists in Russia and the United States, such as H-Bomb physicist Edward Teller, to a theory whose study has been endorsed by such mainstream scientific organizations as the Royal Society, the National Academy of Sciences, and the Intergovernmental Panel of Climate Change. With a friendly ear in the Kremlin and now the White House, the world may see a red dawn rising for geoengineering. This lecture will review its sketchy past and techno-thriller future.

Speaker: Woods Halley, University of Minnesota
4:40 pm:
There will be no seminar this week.

Monday, February 6th 2017
12:15 pm:
Speaker: Brian D. Nord, Fermi National Accelerator Laboratory
Subject: The Power of Galaxy Surveys and Strong Gravitational Lensing for Probing the Cosmos

Current and future galaxy surveys will provide data sets unprecedented in size and precision with which to probe dark energy, dark matter and the early universe through probes like strong gravitational lensing. I will discuss modern experiments, like the Dark Energy Survey (DES) and the Dark Energy Spectroscopic Instrument (DESI) and the opportunities they offer for studying dark energy. In particular, I will discuss the burgeoning role of strong lensing in these surveys, as well as new techniques in deep machine learning that we are deploying in this era of big astronomical data.

Faculty Host: Marco Peloso

Tuesday, February 7th 2017
12:20 pm:
Speaker: Colin Waters, University of Newcastle
Subject: Spatial and temporal development of geomagnetic induced currents (GICs) during the 2015 St Patrick's Day storm

Geomagnetic storms are often associated with elevated solar activity such as coronal mass ejections (CMEs) and sudden impulses (SI). The 17 March, 2015 storm was a G4 level (severe) event with duration of ~18 hours, commencing 14 UT as a result of a CME that occurred on the Sun around 02 UT, 15 March.
The availability of experimental data for monitoring geomagnetic storm events is limited by both instrument response and location. The limitations of comprehensive spatial coverage is a common difficulty. This is particularly acute when attempting to predict storm effects on GIC sensitive infrastructure such as electricity supply grids. Global data collection at low Earth orbit (LEO) can be achieved using engineering magnetometer data obtained from the Iridium satellite constellation which for the first time, are combined with global ground based magnetic field data. These data sets are discussed in the context of the spatial/temporal problem in GIC research and the efforts to predict GIC impacts on electricity supply infrastructure.

4:30 pm:
There will be no seminar this week.

Wednesday, February 8th 2017
1:25 pm:
Speaker: Angela Kou, Yale University
Subject: Building quantum materials with superconducting circuits
Candidate for the Condensed Matter Experimental Assistant Professor Position

Superconducting artificial atoms are created by connecting Josephson junctions, which are nonlinear, non-dissipative elements, to simple electrical circuits. Individual artificial atoms can be coupled using this same toolbox of inductors, capacitors, and Josephson junctions to build novel quantum materials. In this talk, I will discuss prospects for using the fluxonium artificial atom as a building block for topological materials. Topological phases of matter have excitations with exotic quantum statistics and have been proposed as a platform for robust quantum computation. Building a topological material from the bottom-up, however, requires individual components with degenerate ground states and strong coupling between these components.

I will describe two circuits based on the fluxonium artificial atom that meet these requirements. The first circuit is an artificial molecule composed of two strongly-coupled fluxonium artificial atoms, which realizes a Hamiltonian with a dominant σz σz-type interaction between the individual atoms [1]. We find excellent agreement between the measured spectroscopy of the circuit and the theoretically-predicted level transitions, which highlights the suitability of superconducting circuits for implementing tailored quantum systems. Instead of the cosφ energy term characteristic of a Josephson junction, the second circuit realizes an unconventional cos2φ energy term, which results in a nearly-degenerate ground-excited state manifold. Taken together, these circuits fulfill the requirements for the building blocks of topological phases and we can thus start to realize topological materials using superconducting circuits.

[1] A. Kou, et al., arxiv:1610.01094 (2016).

Faculty Host: James Kakalios
To be announced.
4:30 pm:
CM Journal Club in PAN 120
To be announced.

Thursday, February 9th 2017
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
12:05 pm:
Speaker: Ryan Arneson and Lindsay Glesener
3:35 pm:
Speaker: Yongzhong Qian
Subject: Did a Low-Mass Supernova Trigger the Formation of the Solar System? Clues from Stable Isotopes and Be-10
Refreshments to be served outside Smith 100 after the colloquium.

About 4.6 billion years ago, some event disturbed a cloud of gas and dust, triggering the gravitational collapse that led to the formation of the solar system. A core-collapse supernova, whose shock wave is capable of compressing such a cloud, is an obvious candidate for the initiating event. This hypothesis can be tested because supernovae also produce telltale patterns of short-lived radionuclides, which would be preserved today as isotopic anomalies. Previous studies of the forensic evidence have been inconclusive, finding a pattern of isotopes differing from that produced in conventional supernova models. Here we argue that these difficulties either do not arise or are mitigated if the initiating supernova was a special type, low in mass and explosion energy. Key to our conclusion is the demonstration that short-lived Be-10 can be readily synthesized in such supernovae by neutrino interactions, while anomalies in stable isotopes are suppressed.

Friday, February 10th 2017
11:15 am:
There will be no seminar this week.
Speaker: Evan Moen, University of Minnesota
Subject: Transport in Ferromagnetic/Superconducting spin valves
Speaker: Ranjan Laha (Stanford)
Subject: Two new avenues in dark matter indirect detection

Indirect detection is one of the major ways to search for dark matter. However, backgrounds have been a major problem for these searches. In this talk, I will introduce two new techniques to distinguish signal from background. Firstly, I will show how telescopes with ~ 0.1% energy resolution can exploit the Doppler shift of sharp photon features arising from dark matter interactions and separate the signal from background. The technique is general and I will give an example of this search strategy with the 3.5 keV line. In the second half of my talk, I will show how limits from the searches for very high energy photons can be used to constrain dark matter interactions. Using this observable, I will constrain very heavy dark matter which is very difficult to constrain using other means.

Speaker: Thayne Currie, National Astronomical Obs. of Japan, Subaru Telescope
Subject: The Bright Future for Directly Imaging Extrasolar Planets with Extreme Adaptive Optics
Candidate for the MIfA Assistant Professor position

Direct imaging is the new frontier in exoplanet detection and the means by which we will eventually discover a true Earth twin. In this talk, I first will review the advanced methods used to image planets and the wealth of information we have gathered from photometry and spectra of the first imaged planets using Subaru, LBT, and other large telescopes that clarifies key atmospheric properties like clouds, chemistry, and surface gravity. Direct imaging is in the midst of a revolution, driven by the development of extreme adaptive optics" systems that reveal planets 100 times fainter possible than before. I will detail design, capabilities, and first-light discoveries from the newly-commissioned extreme AO system with which I'm involved, the Subaru Coronagraphic Extreme Adaptive Optics system (SCExAO), which shares a technological heritage with LBTAO. Finally, I will close by describing the future promise for SCExAO on Subaru and as a PI instrument on the Thirty Meter Telescope, transformative planned and potential upgrades for LBTAO, and how both systems could work together to image and characterize younger versions of Jupiter in thermal emission to jovian or even rocky, habitable zone planets in reflected light within the next 10-15 years.

3:35 pm:
Speaker: Margaret Schabas, University of British Columbia
Subject: "Thought Experiments in Economics"
Refreshments served at 3:25 p.m.

This paper will demarcate thought experiments from models in economics, and argue that thought experiments and models are distinct types of conceptual tools. There are, however, some models that are near cousins to thought experiments, and vice versa. I will argue that thought experiments are in fact quite rare in economics, past or present. They are launched by a strong if not jarring counterfactual to a distant rather than proximate other world, and the journey the mind then takes back to this world is a familiar one. The paradigmatic case is Hume’s sudden doubling of the money supply, or Friedman’s helicopter drop. But the current rash of thought experiments in environmental economics, as posited by for example Martin Weitzman or Nathaniel Keohane, is misguided. We would be the better for finding a different name for models that speculate well into the future.

Speaker: Dan Dahlberg, University of Minnesota
4:40 pm:
To be announced.

Monday, February 13th 2017
12:15 pm:
Speaker: Zhen Yuan, Shanghai Jiao Tong University
Subject: A possible formation mechanism of Fornax-like dSph: major merger after infall to Milky Way

The extended star formation history of some MW satellites (Fornax, Carina) is always a puzzle in galaxy formation theory on small scales. Similar cases can be also found in M31 satellites. Both Fornax and Carina are estimated to become MW satellites pretty early (~8, ~10 Gyr ago) from proper motion information. The extreme long SFH until recently contradicts the classic galaxy formation models. Some hints from zoom-in MW simulations suggest a possible mechanism of new gas supply is from a companion through major merger after satellite infall. Inspired by the empirical chemical evolution model, I found that Fornax-like dSph needs to be much more diffused in order to explain the elemental abundance pattern ([alpha/Fe] vs. [Fe/H]). It is consistent with the major merger scenario which makes the system expand and consequently a much more inhomogeneous chemical enrichment environment. My collaborators and I made artificial major merger cases of satellites when they infall to MW. Assuming the satellites have some initial stellar configuration, we tracked the evolution of both the dark matter and star particles under growing MW potential. I will discuss our current results and interesting implications.

Faculty Host: Yong-Zhong Qian

Tuesday, February 14th 2017
12:20 pm:
There will be no seminar this week.
4:30 pm:
There will be no seminar this week.

Wednesday, February 15th 2017
1:25 pm:
Speaker: Brian Zhou, Institute for Molecular Engineering, University of Chicago
Subject: Shaping the quantum dynamics of single spins in diamond
Candidate for the Condensed Matter Experimental Assistant Professor Position

The appearance of quantum mechanics on the macroscopic scale underlies some of the most fascinating phenomena in condensed matter physics: topological states arising from Berry phases in electronic bands, and superconductivity from many-body entanglement. Recently, advances in the control and coherence of microscopic quantum systems have enabled these fundamental quantum effects to be studied at the single or few-particle level, as well as be leveraged towards new paradigms for information processing. In this talk, I will focus on experiments using one such system, an atomic-scale defect in diamond known as the nitrogen-vacancy (NV) center. Behaving as a solid-state ‘trapped atom’, the NV center possesses spin and orbital levels, isolated within the host semiconductor’s bandgap, that can be readily manipulated with optical and microwave fields. Through resonant optical excitation, we demonstrate that the NV center spin can be adiabatically evolved to point along arbitrary loops and acquire a Berry phase after the cycle. Such precise quantum control sheds insights on the robustness of geometric phase. Moreover, we accelerate adiabatic dynamics and minimize decoherence by using engineered optical pulses to construct ‘shortcuts’ that absorb deleterious transitions. Finally, I will overview how combining optical and electrical techniques at the atomic level can contribute to applications of material systems in computing, energy, and sensing.

Faculty Host: James Kakalios
To be announced.

Thursday, February 16th 2017
08:00 am:
Untitled in Physics
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
12:05 pm:
Speaker: Evan Tyler and Evan Skillman
3:35 pm:
Speaker: Alberto Nicolis, Columbia University
Subject: String theory in the bathtub
Refreshments to be served outside Smith 100 after the colloquium.

I will describe the peculiar mechanical properties of certain string-like objects that can exist in ordinary fluids and superfluids: vortex lines and vortex rings. I will then show how these properties follow straightforwardly from the principles of effective field theory applied to strings living in a medium.

Faculty Host: Tony Gherghetta

Friday, February 17th 2017
11:15 am:
There will be no seminar this week.
There will be no seminar this week.
Speaker: Masha Baryakhtar, Perimeter Institute
Subject: Searching for Ultralight Particles with Black Holes and Gravitational Waves

The LIGO detection of gravitational waves has opened a new window on
the universe. I will discuss how the process of superradiance,
combined with gravitational wave measurements, makes black holes into
nature's laboratories to search for new light bosons, from axions to
dark photons. When a bosonic particle's Compton wavelength is
comparable to the horizon size of a black hole, superradiance of these
bosons into bound "Bohr levels" extracts energy and angular momentum
from the black hole. The occupation number of the levels grows
exponentially and the black hole spins down. One candidate for such an
ultralight boson is the QCD axion with decay constant above the GUT
scale. Current black hole spin measurements disfavor a factor of 30
(>100) in axion (vector) mass; future measurements can provide
evidence of a new boson. Particles transitioning between levels and
annihilating to gravitons may produce thousands of monochromatic
gravitational wave signals, and turn LIGO into a particle detector.

Speaker: Ian Roederer, University of Michigan
Subject: Heavy Metals from the First Stars to Today
Candidate for the MIfA Assistant Professor position

NASA's Cosmic Origins program aims to address the question, "How did we get here?" My work addresses this question through three broad themes: the nature of the first stars, the formation and evolution of the Milky Way and Local Group, and the origin of the elements. I study dwarf galaxies, globular clusters, and stars in the halo using optical and ultraviolet high-resolution spectroscopic data from various telescopes on the ground and the Hubble Space Telescope. I will present observations of heavy elements that change our understanding of when and how they were first produced in the early Universe, including perhaps by the first stars. Observations of heavy elements in a recently-discovered low-luminosity galaxy, Reticulum II, reveal that the r-process---one of the fundamental ways that stars produce heavy elements---may occur in mergers of neutron stars. At Minnesota, access to instruments at the LBT, MMT, Magellan, and Bok Telescopes would enable critical spectroscopic followup of new stellar systems discovered by the Dark Energy Survey, Pan-STARRS Telescope, and Large Synoptic Survey Telescope in the next decade. These data would help guide our interpretation of observations from the Advanced LIGO/Virgo experiment and the James Webb Space Telescope, and these research directions would present new opportunities for collaboration with the nuclear astrophysics community.

3:35 pm:
Speaker: Heidi Hausse, Princeton University
Subject: "Exploring the Material World of Mechanical Hands in Early Modern Europe"
Refreshments served at 3:25 p.m.

There are few objects that illustrate so well the intersections of medicine, technology, and culture as artificial hands crafted in the sixteenth and seventeenth centuries. Made of metal, wood, leather, and paint, these artifacts suggest the creative and elaborate ways men and women in early modern Europe used to cope with bodily loss. Yet, most early modern hand prostheses sit unnoticed by historians in the shadowy corners of armor exhibits, in museum storage boxes, or tucked away in private collections. This talk shines an investigative light on these objects—from iron arms to wooden hands, and spring-driven finger mechanisms to delicately engraved fingernails. The techniques displayed in such anonymous artifacts, whose wearers and makers remain unknown, show that the problem of bodily loss extended beyond the individual sufferer and his or her family, and into the shops of locksmiths, armorers, clockmakers, woodworkers, and any number of other sites of production.

Co-sponsored with the Center for Early Modern History and the Center for Austrian Studies.

Speaker: Mo Li, University of Minnesota
Subject: Silicon Photonics: Integrated Playground for Novel Optical Physics, Materials, and Applications
4:40 pm:
There will be no seminar this week.

Monday, February 20th 2017
10:00 am:
Thesis Defense in Keller Hall 4-178A
Speaker: Tao Qu, University of Minnesota
Subject: Ferromagnetic Material Properties and Performance in Spintronic Devices
This is the public portion of Ms. Qu's thesis defense. Her advisor is Randall H. Victora.
12:15 pm:
Speaker: Lilya Williams, UMN
Subject:  Interplay between dark and baryonic matter in galaxy centers: new constraints from dynamics and lensing

The central 5-10 kpc of elliptical galaxies, while in long term steady state, are not truly relaxed. The primary reason is that baryons and dark matter are not fully mixed. We demonstrate this by comparing observed and simulated galaxies to theoretically derived prediction for dynamically relaxed collisionless systems, and by examining the observed population of quadruply imaged lensed systems hosted by galaxies. The unrelaxed state can be used to our advantage, to extract information about the formation and evolution of the central regions of galaxies and hence all that they depend on: baryonic processes, central supermassive black hole, and especially dark matter properties. I will describe some ongoing work on this, and sketch future directions.

Tuesday, February 21st 2017
11:30 am:
Speaker: Rajan Gupta, Los Alamos National Laboratory
Subject: In a world with 10 billion people, what will 8 billion do?
Please note change of time, room and day for the seminar, this week only.

Rapid advances in automation, robotization, computerization are changing local and global job markets. Worldwide, the youth are struggling to understandand define a meaningful role for themselves and a promising future for their families. While the future for the innovators, leaders and entrepreneurs is brighter than ever before, a large majority are becoming pessimistic and losing hope. This talk will examine existing trends and correlate many of the current challenges---jobs, poverty, population, migration, climate change, environmental degradation, etc.--- to ask the question, is liberal democracy under threat.

4:30 pm:
There will be no seminar this week.

Wednesday, February 22nd 2017
1:25 pm:
Speaker: Ke Wang, Harvard University
Subject: Manipulating Charge Carriers for Quantum Transport in Van der Waals Materials Nanostructures
Candidate for the Condensed Matter Experimental Assistant Professor Position

Since the discovery of graphene via mechanical exfoliation, it has been shown that the electronic properties of solids can undergo dramatic change when the material thickness is reduced to the atomic limit. Recently, the quality of these 2-dimensional (2D) electronic systems has been significantly improved by hexagonal boron nitrides encapsulation, enabling the electron mean free path only limited by the size of the samples. However, mesoscopic transport studies in these systems are relatively unexplored due to the challenges in the device fabrication processes. Here we develop a robust procedure for making gated-defined nanostructures in 2D van der Waals materials without compromising their intrinsic 2DEG quality, providing versatile experimental platforms to explore various novel quantum phenomena in these systems. By confining and manipulating charge carriers [1][2], we demonstrate relativistic electron-optics, resonant quantum Hall (QH) tunneling spectroscopy, tunable optical trion lifetime and quantized mesoscopic transport in graphene and transition metal dichalcogenides [2]. Our results bode well for addressing many key problems in condensed matter physics, including Luttinger physics, high fidelity logic gates in Loss-DiVincenzo qubits, gate-controlled quantum optics, measurement of small fractional QH energy gaps, and functional quantum devices based on pseudospin manipulation and electron optics.

[1] Wang, et al, Phys. Rev. Lett. 111, 046801 (2013).
[2] Wang, et al, ArXiv:1610.02929 (2016).

Faculty Host: James Kakalios
Planning meeting
4:30 pm:
CM Journal Club in PAN 120
To be announced.

Thursday, February 23rd 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Ragnar Stefansson, University of Minnesota
Subject: To be announced.
12:05 pm:
Speaker: Chris Nolting and Tom Jones
3:35 pm:
Speaker: Daniel Baker, University of Colorado
Subject: Economic and Societal Impacts of Severe Space Weather
Refreshments to be served outside Smith 100 after the colloquium.

This presentation describes extreme space weather impacts and their economic and societal costs. Modern technological society is characterized by a complex set of interdependencies among its critical infrastructures. These are vulnerable to the effects of intense geomagnetic storms and solar storms. Strong currents flowing in the ionosphere can disrupt and damage Earth-based electric power grids and contribute to the accelerated corrosion of oil and gas pipelines. Magnetic storm-driven ionospheric disturbances interfere with high-frequency radio communications and navigation signals from Global Positioning System (GPS) satellites. Exposure of spacecraft to solar particles and radiation belt enhancements can cause temporary operational anomalies, damage critical electronics, degrade solar arrays, and blind optical systems such as imagers and star trackers. Moreover, intense solar particle events present a significant radiation hazard for astronauts during the high-latitude segment of the International Space Station (ISS) orbit as well as for future human explorers of the Moon and Mars. In addition to such direct effects as spacecraft anomalies or power grid outages, a thorough assessment of the impact of space weather events on present-day society must include the collateral effects of space-weather-driven technology failures. For example, polar cap absorption events due to solar particles can degrade – and, during severe events, completely black out – radio communications along transpolar aviation routes. A complete picture of the socioeconomic impact of space weather must include both direct, as well as collateral, effects of space-weather-driven technology failures on dependent infrastructures and services. It is also imperative that we—as a technological society—develop a truly operational space weather observing and modeling system in which the benefits of accurate forecasts are clearly established.

Faculty Host: Roberta Humphreys

Friday, February 24th 2017
11:00 am:
Speaker: Daniel Baker
The seminar will be held on Friday, this week only.
11:15 am:
Speaker: Ming Li and Chris Plumberg, University of Minnesota
Subject: Quark Matter 2017 - Synopsis
11:15 am:
Speaker: Daniel Baker, University of Colorado
Subject: Studying Relativistic Particle Acceleration and Loss in Our Cosmic Backyard: Van Allen Probes Radiation Belt Exploration
Please note change of time, room and day for the seminar, this week only.

Early observations of the Earth’s radiation environment suggested that the Van Allen belts could be delineated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. Subsequent studies showed that electrons in the energy range 100 keV < E< 1 MeV often populated both the inner and outer zones with a pronounced “slot” region relatively devoid of energetic electrons existing between them. The energy distribution, spatial extent and particle species makeup of the Van Allen belts has been subsequently explored by several space missions. However, recent observations by the NASA dual-spacecraft Van Allen Probes mission have revealed wholly unexpected properties of the radiation belts, especially at highly relativistic (E > 2 MeV) and ultra-relativistic (E > 5 MeV) kinetic energies. In this talk we show using high spatial and temporal resolution data from the Relativistic Electron-Proton Telescope (REPT) experiment on board the Van Allen Probes that multiple belts can exist concurrently and that an exceedingly sharp inner boundary exists for ultra-relativistic electrons. Using additionally available Van Allen Probes data, we demonstrate that these remarkable features of energetic electrons are not due to a physical boundary within Earth’s intrinsic magnetic field. Rather it likely that human-generated electromagnetic transmitter wave fields produce such effects suggesting that human-made wave-particle scattering effects deep inside the Earth’s magnetosphere can contribute to an almost impenetrable barrier through which the most energetic Van Allen belt electrons cannot migrate

The seminar has been cancelled for this week. The speaker will be rescheduled for a future date.
Speaker: Yann Mambrini (CNRS, LPT of University Paris XI)
Subject: Historical Dark Matter Papers
Speaker: Patrick Kelly, University of California - Berkeley
Subject: Using Galaxy Cluster Lenses as Extreme Probes
Candidate for the MIfA Assistant Professor position

Galaxy clusters can highly magnify galaxies behind them, making cluster lenses powerful tools for studying the high-redshift universe. The James Webb Space Telescope, when pointed towards foreground cluster fields, will be sensitive to even low-luminosity galaxies at redshift z > 6 (~35th magnitude) thought to drive reionization. In regions of high magnification, however, cluster magnification maps show strong disagreements. I will describe the first-known multiply imaged, strongly lensed supernova (SN), which appeared in late 2014 in an Einstein cross configuration in the MACS1149 galaxy-cluster field. The timing of the reappearance of the SN, at an offset of ~8 arcseconds, in 2015 disagrees with most but not all predictions, and illustrates a promising approach for identifying the most accurate cluster-modeling techniques and magnification maps. I will next discuss observations of an individual star at high redshift, which acts as a new window into the nature of galaxy-cluster dark matter. Detections of hundreds of thousands of SNe and thousands of lensed transients by the Large Synoptic Survey Telescope and the Wide-Field Infrared Survey Telescope will allow new insights into star formation and stellar evolution beginning at z~15-20, as well as the nature of dark matter and dark energy.

3:35 pm:
Speaker: Robert Schulmann, The Einstein Papers Project
Subject: "Albert Einstein: Political Consistency in Volatile Times"
Refreshments served at 3:25 p.m.

There is a remarkable consistency in Einstein’s views on physics and politics, and in his personal relations. In concentrating on political aspects of the Einstein trajectory, I will stress the continuities, above all the moral consistencies that underpinned his political evolution and that explain at least in part the hold he still has on us. Ever the non-conformist, it is Einstein’s sensitivity to the plight of the underdog, to the weaker members of society, and to the outsider that serves as the major contributing factor. I plan to tease out some strands that have particular significance in the present political situation.

Speaker: Rafael Fernandes, University of Minnesota
4:40 pm:
There will be no seminar this week.

Monday, February 27th 2017
12:15 pm:
Speaker: Patrick Meyers, UMN
Subject: Searching for the stochastic gravitational-wave background in Advanced LIGO's first observing run

One of the most exciting prospects of gravitational-wave astrophysics and cosmology is the measurement of the stochastic gravitational-wave background. In this talk, we discuss the most recent searches for a stochastic background with Advanced LIGO—the first performed with advanced interferometric detectors. We search for an isotropic as well as an anisotropic background, and perform a directed search for persistent gravitational waves in three promising directions. Additionally, with the accumulation of more advanced LIGO data and the anticipated addition of Advanced Virgo to the network in 2017, we can also start to consider what the recent gravitational-wave detections—GW150914 and GW151226—tell us about when we can expect a detection of the stochastic background from binary black hole coalescences.

Tuesday, February 28th 2017
12:20 pm:
Speaker: John Dombeck, Physics, U Minnesota
Subject: Field-Aligned Currents and Auroral Precipitation Mechanisms in the Earth's Magnetosphere

Field-aligned currents (FACs) provide a fundamental driver and means of Magnetosphere-Ionosphere (M-I) coupling. These currents need to be supported by local physics along the entire field line generally with quasi-static potential structures, but also to support the time-evolution of these structures and currents Alfvén waves are required which can produce Alfvénic electron acceleration. In regions of upward current, precipitating auroral electrons are accelerated earthward. These processes can result in ion outflow, changes
in ionospheric conductivity, and affect the particle distributions on the field line, affecting the M-I coupling processes supporting the individual FACs and potentially the entire FAC system. The FAST mission was well suited to study both the FACs and the electron auroral acceleration processes. We present the results of the comparisons between meso- and small-scale FACs determined from FAST using the method of Peria, et al., 2000, and our FAST auroral acceleration mechanism study when such identification is possible for the entire ~13 year FAST mission.

Wednesday, March 1st 2017
11:00 am:
Speaker: Maria Navarro Gastiasoro, UMN
Subject: Emergent disorder phenomena in correlated Fe-based superconductors
Note change of time and day for the seminar.

The fundamental pairing mechanism causing high-T superconductivity in Fe-based superconductors remains controversial. Superconductivity is only one of several phases exhibited by these materials, and it is widely believed that the mechanism responsible for pairing may be closely linked to the existence of other proximate ordered phases. Most of these materials are obtained by chemical doping, which besides extra carriers, introduces disorder in the system. Therefore, understanding the role of these impurities is crucial and it has been a main focus of our work.

Faculty Host: Rafael Fernandes
1:25 pm:
Practice talks for APS March Meeting
Speaker:  Abner Soffer, Tel Aviv University
Subject: New physics with long-lived particles
4:30 pm:
CM Journal Club in PAN 120
Subject: Short meeting

Thursday, March 2nd 2017
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
12:05 pm:
Speaker: Tony Young and Julius Donnert
3:35 pm:
Speaker: Alisa Bokulich, Department of Philosophy, Boston University
Refreshments served at 3:15 p.m.
3:35 pm:
Speaker: Francis Halzen, University of Wisconsin-Madison
Subject: IceCube: Cosmic Neutrinos and More
Refreshments to be served outside Smith 100 after the colloquium.

The IceCube project has transformed one cubic kilometer of natural Antarctic ice into a neutrino detector. The instrument detects more than 100,000 neutrinos per year in the GeV to PeV energy range. Among those, we have isolated a flux of high-energy cosmic neutrinos. I will discuss the instrument, the analysis of the data, and the significance of the discovery of cosmic neutrinos. The observed cosmic neutrino flux implies that accelerated protons, and not just electrons, generate a significant fraction of the energy in the non-thermal universe. I will also discuss the study of the neutrinos themselves in the wide energy range revealed by IceCube.

Faculty Host: Clement Pryke

Friday, March 3rd 2017
11:15 am:
Speaker: Ming Li and Chris Plumberg, University of Minnesota
Subject: Quark Matter 2017 - Synopsis
Practice talks for APS March Meeting
Speaker: Ryo Namba (McGill)
Subject: Gravitational wave signals from low-energy inflation

Detection of tensor mode fluctuations at the largest cosmological scales is often expected to provide a robust evidence of inflation and to fix the inflationary energy scale. Such direct connection is however applicable only when the tensor perturbations are originated from their quantum fluctuations during inflation and are effectively decoupled from other energy contents. We consider a case exceptional to this lore. When an SU(2) gauge field is present and is prevented from diluting away by a coupling to a pseudo-scalar, the configuration of the SU(2) vev preserves the background isotropy, and on this geometry, the SU(2) perturbations introduce an additional tensor mode. The substantial growth experienced by this mode is then transferred to the true tensor fluctuations of the metric already at the linear level. While these fields are energetically subdominant to the inflaton, their perturbations can be considerably larger than the standard amplitude. We discuss several potential constraints on the mechanism and demonstrate that detectable tensor mode signals even for low energy inflation.

Speaker: Andrew Mann, University of Texas - Austin
Subject: Tracing Planetary Evolution from Formation to Maturity
Candidate for the MIfA Assistant Professor position

Planets are not born in their final state; rather, they change significantly over their lifetimes. Understanding how planets evolve has been a central question since the discovery of the first exoplanets. The first few hundred million years are thought to be the most formative, but planets in this age range are also the most difficult to identify and characterize. Instead, research has focused on inferring the history of planets through patterns in the population of older systems. In this talk I will discuss how this paradigm is shifting, as novel search techniques and new missions have enabled our discovery of Earth- to Neptune-size planets as young as 10 Myr. These discoveries have altered our understanding of how planets migrate and lose atmosphere, but raise further questions about the physical drivers of these changes. The upcoming TESS mission will discover hundreds more young planets, including analogues of a young Earth. Combined with follow-up from NIR spectrographs (e.g., iLocater on LBT), the TESS sample will enable new tests of planet formation and evolution through population statistics. Eventually, JWST, LBT, and 30m-class telescopes can be used to study the atmospheres of young, rocky planets, providing unique insight into the history of potentially habitable planets.

3:35 pm:
Speaker: Stacey Van Vleet, University of California - Berkeley
Subject: "Edible Networks: Precious Pills as Technologies of Medical Governance in Qing China"
Refreshments served at 3:25 p.m.

Between the seventeenth and the early twentieth century, Tibetan Buddhism grew from a regional system of governance to one at the heart of the Qing Empire (1644-1911) ruling China and Inner Asia. A crucial factor in this growth was the Qing rulers' adoption of Tibetan Buddhist medical institutions and technologies, in a concerted imperial strategy to consolidate administration of the frontiers by promoting medical training, treatment, and ritual. Tibetan Buddhist monastic colleges in the Qing Empire practiced medical technologies from smallpox innoculation to moxibustion and bonesetting, but became best known for their production of "precious pills" (rin chen ril bu), or the consecrated, edible products of ritual assemblies. In this talk, I demonstrate how precious pills during the Qing period developed as technologies of collecting and compounding expensive ingredients from far-flung regions of the empire, materializing the experience of a multi-ethnic Buddhist community as a consecrated "edible network." Understanding precious pills as medical technologies available for imperial adoption and redevelopment, I argue, reveals how they served not only to engineer physical health and spiritual growth, but also to engineer remedies for conflict and building community.

Speaker: Vincent Noireaux, University of Minnesota
Subject: DNA programmed dynamical systems outside cells: from gene circuits to self-assembly
4:40 pm:
There will be no seminar this week.

Monday, March 6th 2017
12:15 pm:
Speaker: Darryl Wright, UMN
Subject: Supernova Hunters: combining human and machine classifications

Efficient identification and follow-up of astronomical transients is hindered by the need to manually select promising candidates from data streams that contain many false positives. With data from Pan-STARRS1 we present the citizen science project, Supernova Hunters created with the Zooniverse project builder. The project allows us to crowdsource classifications of supernova candidates, and test methods to combine human and machine classifications. We show this combination produces a purer and more complete sample of supernovae than either individually.

Speaker: Lior Kornblum, Technion - Israel Institute of Technology
Subject: When Functional Oxides Meet Semiconductors
Note: Change of date and time of seminar.

Perovskite oxides of transition metals offer scientists and engineers a theme park of exciting and often unexpected physics, with complex structure-property relations and a wide scope of useful phenomena. Advances in epitaxial growth techniques bring unprecedented possibilities of atomic engineering of these oxides and their interfaces, with exciting prospects of unravelling their underlying physics and harnessing it towards useful applications. However, fundamental material challenges inhibit the introduction of these materials onto semiconductors and thus into the microelectronics technology.

The potential of the oxides’ functionalities to evolve out of the labs and into technology has received a considerable boost with the pioneering of epitaxial growth approaches for perovskites directly on semiconductors. This combination opens a route to bridge between oxide functionalities and microelectronics. Moreover, interface engineering of oxides on semiconductors can lead to new functionalities, made possible by the coupling between the dissimilar materials.

The challenges and the opportunities of oxide-semiconductor integration will be demonstrated with two examples. First, results on integrating oxide interfaces that exhibit 2D electron gas (2DEG) with semiconductors will be presented, and their challenges and opportunities discussed. The second example will revolve around the integration of epitaxial oxides with semiconductors for renewable energy. The ability to synergistically combine the advantages of these two classes of materials, while mitigating their deficiencies, is put to the test in solar water splitting into hydrogen fuel. Detailed analysis of the device energetic structure highlights the advantages of this combination, and charts a clear route for improving the efficiencies using well-established semiconductor technology.

With these examples I hope to provide a glimpse into the prospects of combining functional oxides with semiconductors, and illustrate the promise of combining engineering and physics towards creating new devices and future technologies.

Faculty Host: Bharat Jalan

Tuesday, March 7th 2017
12:20 pm:
Speaker: Terry J. Jones, U Minnesota, MN Institute for Astrophysics
Subject: Magnetic Fields, Grain Alignment, and You

Observations of polarization caused by dust grains aligned with the
magnetic field is a major tool for studying the magnetic field geometry
in regions ranging in size from entire galaxies, down to planetary
systems and stellar winds. The alignment mechanism, however, has eluded
astronomers for over 50 years. After these years of frustration, we now
seem to be closing in on an understanding of the alignment mechanism,
which I will discuss.

3:30 pm:
Speaker: Damjan Pelc, University of Zagreb
Subject: Percolative aspects of cuprate superconductivity

One of the central problems in the physics of the cuprate high-temperature superconductors is understanding the superconducting emergence regime above the macroscopic critical temperature Tc. The emergence regime provides crucial information about both the normal and superconducting states and has long been the subject of controversy. Experimentally, it is difficult to separate the nascent superconducting response from the complex normal-state behavior, with different experimental probes leading to disparate conclusions. We present a systematic investigation of the emergence of superconductivity in the cuprates using an unconventional probe: nonlinear conductivity. This probe eliminates background subtraction problems because the signal vanishes in the normal state. Through experiments on several cuprate families and as a function of doping, we show that the emergence regime is universally confined to a narrow temperature range, but incompatible with standard Ginzburg-Landau theory. Instead, a single characteristic temperature scale T0 controls superconductivity emergence. To explain the experiments, we introduce a simple superconducting percolation model based on local gap disorder, which provides a quantitative description of our measurements and explains several puzzling prior results. The success of the percolation model shows that intrinsic disorder plays an important role in cuprate superconductivity, enabling us to create an overarching picture of the charge-carrier behavior in the cuprates.

Faculty Host: Martin Greven

Wednesday, March 8th 2017
1:25 pm:
Speaker: Anthony Leggett, University of Illinois Urbana-Champaign
Subject: Reflections on the past, present and future of condensed matter physics

I consider some of the ways in which the practice and even the definition of "condensed-matter physics" has evolved since its inception in the early twentieth century, with particular reference to its relationship to neighboring and even distant disciplines. I speculate on some possible directions in which the discipline may develop over the next few decades, emphasizing that there are still some very basic questions to which we currently have no satisfactory answers.

Faculty Host: Martin Greven
Speaker: Paper Discussion
Subject: Improved measurement of |V(ub)| with inclusive semileptonic B decays. CLEO Collaboration.

Paper Discussion: "Improved measurement of |V(ub)| with inclusive
semileptonic B decays". CLEO Collaboration.

Anyone can join the discussion. Please try to read the paper before the seminar. You can find it at http://inspirehep.net/record/582690

Thursday, March 9th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Prof. Thomas Gregor, Princeton University
Subject: How the physics of enhancers shapes development

Enhancers are small regulatory pieces of DNA that control the activity of genes, which eventually determine cellular fates during the development of multicellular organisms. They need to measure the concentrations of various input effector molecules, called transcription factors, and then act over often very long distances along the DNA in order to activate a distantly located gene. In this talk I will present my laboratory’s progress on two fundamental physical properties of these enhancers: 1. How do enhancers decode the information of the input transcription factors and then transduce it into a precise output? 2. How do enhancers operate at long distances to instruct gene activity? We use a combination of genome editing, live imaging and statistical mechanics techniques to address these questions in the fruit fly embryo.

11:00 am:
Thesis Defense in PAN 110
Speaker: Yangmu Li
Subject: New insights into phase diagram and the emergence of superconductivity for the electron-doped cuprate superconductors
This is the public portion of Mr. Li's thesis defense. His advisor is Professor Martin Greven.

After three decades of enormous scientific inquiry, the emergence of superconductivity in the cuprates remains an unsolved puzzle. One major challenge has been to arrive at a satisfactory understanding of phase transitions in the multi-parameter phase space. A related challenge has been to achieve a unified understanding of the hole- and the electron-doped compounds. Here, I report detailed neutron scattering, muon spin rotation/relaxation and magnetoresistivity measurements for the archetypal electron-doped cuprate Nd2-xCexCuO4+d that, in combination with prior data, provide crucial links between the normal and superconducting states and between the electron- and the hole-doped parts of the phase diagram. The revised electron-doped side of the phase diagram features a disorder-smeared first-order phase transition between the antiferromagnetic and bulk superconducting ground states. The characteristics of the normal state and those of the superconducting state consistently indicate two-band (electron and hole) features and clearly point to hole-driven superconductivity in these nominally electron-doped materials. These insights allow us to extend the Uemura-scaling between the superconducting transition temperature and the hole superfluid density to the electron-doped cuprates.

Speaker: Johannes Reuther, Freie Universitat Berlin
Subject: Functional renormalization group - a new approach to frustrated quantum magnetism

The experimental and theoretical investigation of quantum spin systems has
become one of the central disciplines of contemporary condensed matter
physics. From an experimental viewpoint, the field has been significantly
fueled by the recent synthesis of novel strongly correlated materials with
exotic magnetic or quantum paramagnetic ground states. From a theoretical
perspective, however, the numerical treatment of realistic models for
quantum magnetism in two and three spatial dimensions still constitutes a
serious challenge. This particularly applies to frustrated systems, which
complicate the employment of established methods. This talk gives an
introduction into the pseudofermion functional renormalization group
(PFFRG) technique which represents a novel approach to determine large
size ground state correlations of a wide class of spin Hamiltonians. Using
a diagrammatic pseudofermion representation for quantum spin models, the
PFFRG performs systematic summations in all two-particle fermionic
interaction channels, capturing the correct balance between classical
magnetic ordering and quantum fluctuations. We first apply the PFFRG
method to spin models on the 2D square and kagome lattices and benchmark
our results against other numerical methods. A particular focus is on the
recently synthesized compound Ca10Cr7O28 which in neutron scattering, muon
spin relaxation and thermodynamic susceptibility measurements shows all
signatures of a quantum spin liquid. Applying the PFFRG technique to a
bilayer kagome model we are able to reproduce the spin fluctuations
measured in neutron scattering and confirm the non-magnetic ground state
of this compound.

Faculty Host: Natalia Perkins
12:05 pm:
Speaker: Trevor Knuth and Larry Rudnick
3:35 pm:
Speaker: Anthony Leggett, University of Illinois at Urbana-Champaign
Subject: Superfluidity, phase coherence and the new Bose-condensed alkali gases
Refreshments to be served outside Smith 100 after the colloquium.

The phenomenon of superfluidity was discovered in liquid helium nearly sixty years ago, and ever since, following the almost immediate suggestion of Fritz London, it has been the almost universal belief in the condensed-matter community that it is due to the onset of the phenomenon of Bose-Einstein condensation which is theoretically predicted to occur in that system at sufficiently low temperature. However, for various practical reasons, it is extremely difficult even to establish unambiguously that BEC is occurring in 4-He, let alone to test directly some of the ideas which connect it to superfluidity. The recent attainment of BEC in dilute atomic alkali gases opens a new arena in this respect, allowing us to do many experiments which we would have loved to do in 4-He, but which are in practice unfeasible in that system. In this talk, I first review briefly the fundamental ideas developed in the helium context, then give a general introduction to the physics of the BEC alkali gases, and finally discuss some of the novel possibilities they open up, both already realized and still on the drawing-board.

Faculty Host: Martin Greven

Friday, March 10th 2017
Speaker: Yang Tang, University of Minnesota
Subject: Neutron scattering study of the unusual magnetic order in cuprate superconductors
Speaker: Sam McDermott (Stonybrook)
Subject: Supernova Bounds on Dark Sectors

Supernova 1987A created an environment of extremely high temperatures and nucleon densities. The rough agreement between predictions of core collapse models and observations of a "neutrino burst" provide an opportunity to set bounds on a wide range of theories of new physics. We present new bounds on dark sector models, incorporating finite-temperature effects on the production and trapping for the first time, and also utilizing a more realistic model of the high-mixing parameter space than in previous work. This has dramatic effects for the landscape of such models.

1:30 pm:
Speaker: Dr. Evan Grohs
Subject: Big bang nucleosynthesis in high precision neutrino cosmology
Note change in time for this week.

Cosmic microwave background Stage-IV experiments and thirty-meter-class telescopes will come on line in the next decade. The convolution of these data sets will provide on order 1% precision for observables related to neutrino cosmology. Beyond Standard Model (BSM) physics could manifest itself in slight deviations from the standard predictions of quantities such as the neutrino energy density and the primordial abundances from Big Bang Nucleosynthesis (BBN). In this talk, I will argue for the need for precise and accurate numerical calculations of BBN. I will first show the detailed evolution of the neutrino spectra as they go out of equilibrium with the plasma. The spectra are important in changing the ratio of neutrons to protons. I will show how sensitive the primordial mass fraction of helium is to the weak interaction rates which evolve the neutron-to-proton ratio. Finally, I will present an example of how BSM physics can affect BBN by instituting an asymmetry between neutrinos and antineutrinos, commonly characterized by a lepton number.

There will be no colloquium this week.
3:35 pm:
Subject: No HSTM/MCPS Colloquium this Week
Speaker: Paul Crowell
4:40 pm:
Speaker: Peter Bohacek, Sibley High School
Subject: Pivot Interactives (nee Direct Measurement Video Project)

Pivot Interactives is an outgrowth of our five year work on the Direct Measurement Video project. Pivot Interactives is a web platform that allows teachers to create web-based activities that combine matrices of Direct Measurement Videos with other interactive tools such as data tables, graphs, and curve fitting, interactive questions, and student feedback. Within the Pivot Interactives Portal, teachers can assign these activities to students. Students use any web-connected device to complete the activity and submit for teacher feedback. This allows students to conduct inquiry-based learning using all steps eight science in an online environment.

After a quick tour of the platform, we'll explore how Pivot Interactives can be used to facilitate learning labs skills such as model making and testing, linearization, and finding the meaning of slope and intercept.

Wednesday, March 15th 2017
1:25 pm:
No seminar; Spring Break

Thursday, March 16th 2017
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week. Spring Break.
12:05 pm:
No Journal Club; Spring Break
3:35 pm:
There will be no colloquium this week due to Spring Break

Friday, March 17th 2017
No condensed matter lunch this week.
Speaker: NO SEMINAR- SPRING BREAK
1:30 pm:
No seminar; Spring Break
No Colloquium; Spring Break
3:35 pm:
Subject: No HSTM/MCPS Colloquium for Spring Break
No seminar, Spring Break
4:40 pm:
There will be no seminar this week.

Monday, March 20th 2017
12:15 pm:
Speaker: Hugh Dickinson, UMN
Subject:  Visual Classification of Illustris Galaxy Morphologies: Evaluating Cosmological Simulations using Galaxy Zoo

Illustris is one of the first large-scale simulation projects with sufficient resolution and physical realism to model the evolution of galaxy-sized structures within a wider cosmological context. If synthetic observational data for the Illustris galaxies accurately emulate observations of galaxies in the real Universe, then arguments for corresponding parity between physics and history of galaxy formation in simulation and reality and become more credible. Conversely, discrepancies between the simulated and observed populations can be used to infer shortcomings of the Illustris simulation and identify avenues for its potential enhancement.

I will briefly review two traditional approaches that have already been used to quantify the degree of correspondence between simulated and observed galaxy properties. I will then introduce an ongoing initiative to obtain visual morphological classifications for the Illustris galaxies using the Galaxy Zoo citizen science platform. Comparing the initial results of this study with identically obtained data for galaxies observed by the Sloan Digital Sky Survey indicates substantial mismatches between the visual appearance of the real and simulated datasets. I will explore the contexts in which these disparities are apparent before discussing plausible explanations for their origin and promising avenues for further investigation.

Tuesday, March 21st 2017
12:20 pm:
Speaker: Scott Thaller
Subject: Evidence for modulations of the cold plasma density and convection in the inner magnetosphere being driven at the solar rotation period

"In this talk I will present work we have done with Van Allen Probes data which provides strong evidence for solar rotation modulation of the plasmapause location, dawn-dusk electric field, and cold plasma density from 2.5 < L < 5. In this research we show that the solar rotation modulation of the inner magnetosphere is prominent during the declining phase of the solar cycle when there is a heightened occurrence of fast solar wind streams routinely passing over the earth at the solar rotation period, called Co-rotating Interaction Regions (CIRs). The occurrence of enhanced periods of geomagnetic activity being driven by the CIRs every ~27 days leads to modulation of the plasmasphere on that timescale. In contrast, during solar maximum when the geomagnetic activity in the magnetosphere is more likely to be driven by CMEs, the solar rotation modulation is less prominent, if at all present. I will also present research we have conducted on the cold plasma outflows that occur during geomagnetic activity, including outflows driven at the solar rotation period.

4:30 pm:
There will be no seminar this week.

Wednesday, March 22nd 2017
1:25 pm:
Speaker: Chris Hooley, University of St. Andrews
Subject: Feynman path integrals over matrix product states: insights into unconventional phase transitions

An interesting topic in the theory of quantum phase transitions is that of the transition between a classically ordered state, such as a Néel state, and a quantum ordered state, such as a valence bond crystal. On the classically ordered side of the transition, we have a well developed understanding based on the spontaneous breaking of a continuous symmetry and the occurrence of associated Goldstone modes (spin waves). On the quantum ordered side, things are rather less clear. Even the description of the quantum ordered state itself is not straightforward, since it is not a saddle-point of the usual spin-coherent-state path integral.

In this talk, I shall present an approach designed to address this problem by constructing the path integral over matrix product states rather than spin coherent states. This allows both classically ordered states (which are matrix product states of bond dimension 1) and quantum ordered states (which are matrix product states of higher bond dimension) to be captured on an equal footing. I shall use this approach to show that, for at least one example of such a transition, a Landau-Ginzburg-Wilson-type description can be given, where the ‘order parameter’ is a field representing the nearest-neighbour entanglement of the spins.

The talk is designed to be entirely self-contained: in particular, no prior knowledge of matrix product states or quantum ordered phases is assumed. The work about which I shall speak was undertaken in collaboration with Andrew Green (University College London), Jonathan Keeling (St Andrews), and Steve Simon (Oxford), under the auspices of the TOPNES programme. Most of the details can be found at https://arxiv.org/abs/1607.01778.

Faculty Host: Rafael Fernandes
To be announced.
4:30 pm:
CM Journal Club in PAN 120
Speaker: Xuzhe Ying
Subject: Commensurate Incommensurate transition

Thursday, March 23rd 2017
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
12:05 pm:
Subject: There is no Journal Club this week.
3:35 pm:
Speaker: Nandini Trivedi, Ohio State University
Refreshments to be served outside Smith 100 after the colloquium.

A superconductor is a perfect conductor and a perfect diamagnet in which currents flow with zero resistance and screen external magnetic fields. This emergent state of electrons has been described successfully by the Bardeen-Cooper-Schrieffer (BCS) paradigm. Within this standard paradigm, superconductivity arises when the Fermi surface in a normal metal becomes unstable to pairing. What happens when this paradigm breaks down, for example, in systems with very small Fermi surfaces, or in the absence of a Fermi surface altogether, as in a band insulator? In this talk I will provide some answers and also show how exciting new directions for superconductivity and superfluidity research are opening up in quantum materials and ultra-cold atomic gases.

Faculty Host: Fiona Burnell

Friday, March 24th 2017
11:15 am:
There will be no seminar this week.
12:20 pm:
Speaker: David Harrison, University of Minnesota
Subject: Measurements of 1/f Noise in CuMn Thin Films
Note change of room, this week only.
Subject: Phenomenology of gauge and fermion-preheating and the end of axion inflation

Axions are attractive candidates for theories of large-field inflation that are capable of generating observable primordial gravitational wave backgrounds. These fields enjoy shift symmetries that protect their role as inflatons from being spoiled by coupling to unknown UV physics. This symmetry also restricts the couplings of these axion fields to other matter fields. At lowest order, the only allowed interactions are derivative couplings to gauge fields and fermions. These derivative couplings lead to the biased production of fermion and gauge-boson helicity states during and after inflation. I will describe some recent work on reheating in axion-inflation models that are derivatively coupled to Abelian gauge-fields and fermion axial-currents. The biased production of fermion helicity-states in these theories has interesting phenomenological implications for leptogenesis, while gauge preheating in this class of models can be extremely efficient, and can result in cosmologically relevant magnetic fields.

Speaker: Charles 'Chick' Woodward
Subject: Small Worlds – New Vistas

Our solar system contains a surprising diversity of planetary environments whose import has direct bearing on understanding the condensation of materials out of a cooling solar nebula, planetesimal evolution, and the eventual migration of giant worlds beyond the frost line to new orbital positions. Highlighted during this presentation will be recent observational exploration of solar system small bodies, with new remote sensing techniques from ground-based and space-based facilities motivated by the question: How have the myriad chemical and physical processes that shaped the solar system operated, interacted, and evolved over time? Vistas within our solar system shed light on processes that are likely repeated among the plethora of exo-planetary systems and may help us how comprehend how common life might be.

3:35 pm:
Speaker: Lee Vinsel, Stevens Institute of Technology
Subject: "Making Maintainers: A Place for History in an Age of Innovation-Speak and Endless Tech Hype"
Refreshments served at 3:25 p.m.

Our culture is obsessed with innovation, which is thought to be the goal of business, policy-making, philanthropy, education, even play. Yet, the vast majority of human activity aims not at creating or adopting innovative things but in maintaining old ones. This talk first traces the rise of innovation-speak in the USA before turning to an alternative view of human life with technology that focuses on maintenance, repair, and mundane labor, a long tradition of thought that includes historians like Ruth Schwartz Cowan and David Edgerton.

4:40 pm:
Speaker: Shaul Hanany, University of Minnesota
Subject: From the status of the Universe to the status of the planet, the best research group around
Note change of location for this week only.
4:40 pm:
Speaker: Brita Nellermoe, University of St. Thomas
Subject: Student Study Practices, Self-Efficacy, and Classroom Performance

Student surveys from the introductory Physics classes at the University of St. Thomas explore the relationships between student study practices, self-efficacy and classroom performance, including test and class grades. Short-answer surveys were given to a total of approximately 100 students, evenly divided between Calculus-based introductory Physics and Algebra-based introductory Physics. These short answer surveys have been coded and correlated to student grades and in-class observed practices. This talk will discuss preliminary results of the study, both surprising and not, possible further areas of exploration and the relationship with related studies.

Monday, March 27th 2017
12:15 pm:
Speaker: Qi Wen, UMN
Subject:  Falling Rotation Curves of The Star-forming Galaxies Ten Billion Years Ago

In the standard model of cosmology, the mass ratio of baryons to dark matter is about 1 : 5. The mass of the outer disks in nearby (z ~0) massive galaxies are usually dominated by dark matter, which explains the observations of the common flat or slightly rising shapes of galaxies' rotation curves in the local universe. However, a recent study reported that the rotation curves of star-forming galaxies at z ~ 0.6-2.6 may commonly be falling with radius. In this talk, I will discuss this study in detail about their observations, sample selection and methodology. Finally we will look at some implications from the results obtained.

Tuesday, March 28th 2017
12:20 pm:
There will be no seminar this week.
4:30 pm:
There will be no seminar this week.

Wednesday, March 29th 2017
1:30 pm:
There will be no seminar this week.
Speaker: Aaron Mislivec, University of Minnesota
Subject: Neutrino-Nucleus Coherent Pion Production at MINERvA

Neutrino-nucleus coherent pion production is a rare neutrino scattering process that produces a lepton and pion in the forward direction while leaving the target nucleus in its initial state. Despite being rare, coherent pion production is an important background to neutrino oscillation measurements. Previous measurements of coherent pion production in the 1 to 10 GeV neutrino energy range, the energy range in which neutrino oscillation experiments operate, have been limited by either low statistics or detector capabilities. MINERvA, a dedicated neutrino-nucleus scattering experiment, has made precise measurements of neutrino and antineutrino charged current coherent pion production on carbon at 2 to 20 GeV neutrino energies. These measurements are an important input to neutrino-nucleus interaction models utilized by neutrino oscillation experiments.

4:30 pm:
CM Journal Club in PAN 120
Speaker: Mengxing Ye
Subject: Kitaev Spin Liquid
Refreshments will be served.

I will follow Kitaev's original paper [1] and show how the Kitaev honeycomb model can be solved exactly by reduction to free fermions (in a static Z2 gauge field). It is also a good example to see how "quantum order", which pertains to quantum spin liquid, emerges in the spin system. I will try to make the talk friendly to junior graduate students, and the derivation only requires graduate level quantum mechanics.

[1] A. Kitaev, 'Anyons in an exactly solved model and beyond'

Thursday, March 30th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Prof. Peter Kner, University of Georgia
Subject: Wavefront Correction for Superresolution Microscopy

Superresolution microscopy is rapidly becoming an essential tool in the biological sciences allowing imaging biological structure at length scales below 250 nm. Currently, superresolution microscopy has been applied successfully on single cells achieving resolutions of 100nm down to 20nm over a few microns of depth. When superresolution microscopy is applied in thicker samples the resolution rapidly degrades. Optical aberrations and scattering distort and reduce the point spread function causing different superresolution techniques to fail in different ways. I will discuss our work on combining structured illumination microscopy and stochastic optical reconstruction microscopy with adaptive optics to achieve sub-diffraction resolution in thick tissue.

12:05 pm:
Speaker: Matt Gomer and Liliya Williams
3:35 pm:
Speaker: Alex Koulakov, Cold Spring Harbor Laboratory
Subject: Mechanism of Olfaction
Refreshments to be served outside Smith 100 after the colloquium.

Olfaction is the final frontier of our senses - the one that is still almost completely mysterious to us. Despite extensive genetic and perceptual data, and a strong push to solve the neural coding problem, fundamental questions about the sense of smell remain unresolved. Unlike vision and hearing, where relatively straightforward relationships between stimulus features and neural responses have been foundational to our understanding sensory processing, it has been difficult to quantify the properties of odorant molecules that lead to olfactory percepts. In a sense, we do not have olfactory analogs of red, green and blue''. The seminal work of Linda Buck and Richard Axel identified a diverse family of about 1000 receptor molecules that serve as odorant sensors in the nose. However, the properties of smells that these receptors detect remain a mystery. I will review our current understanding of the molecular properties important to the olfactory system. I will also describe a theory that explains how odorant identity can be preserved despite substantial changes in the odorant concentration.

Faculty Host: Boris Shklovskii

Friday, March 31st 2017
11:15 am:
Speaker: Cheng-Hsien Li, University of Minnesota
Subject: Density Matrix Treatment of Neutrino Oscillations In Vacuum

Motivated by our earlier estimate that shows an enormous degree of overlap among neutrino wave packets (WPs) from astrophysical sources, I will present a derivation of vacuum oscillation probability for detecting one neutrino from a pair of neutrino WPs which are described by an anti-symmetric 2-particle wave function. I will begin by briefly reviewing the oscillation probability in the one-particle framework and recast the probability as the expectation value of a projection operator which projects a neutrino WP state onto the detected WP state. In the two-particle framework, such expectation value can be computed with the help of the density matrix of the 2-particle wave function. Additional interference terms in the derived oscillation probability appear to be invariant under arbitrary re-phasing of the relevant WP states but these terms will nevertheless vanish due to the orthogonality between the two neutrino WPs. Therefore, the derived oscillation probability reduces to a simple sum of one-particle oscillation probabilities.

Speaker: Daniel Shaffer, University of Minnesota
Subject: Searching for Topological Superconductivity in MoS_2 (and other transition metal dichalcogenides)
Speaker: Alex Kamenev (UMN)
Subject: TBA
There is no colloquium this week.
3:35 pm:
Subject: Author Meets Readers: David M. Miller's "Representing Space in the Scientific Revolution"
Refreshments served at 3:25 p.m.

Katherine Brading, Philosophy, University of Notre Dame

Samuel Fletcher, Philosophy, University of Minnesota

Edward Slowik, Philosophy, Winona State University

Abstract: The novel understanding of the physical world that characterized the Scientific Revolution depended on a fundamental shift in the way its protagonists understood and described space. At the beginning of the seventeenth century, spatial phenomena were described in relation to a presupposed central point; by its end, space had become a centerless void in which phenomena could only be described by reference to arbitrary orientations. David Marshall Miller examines both the historical and philosophical aspects of this far-reaching development, including the rejection of the idea of heavenly spheres, the advent of rectilinear inertia, and the theoretical contributions of Copernicus, Gilbert, Kepler, Galileo, Descartes, and Newton. His rich study shows clearly how the centered Aristotelian cosmos became the oriented Newtonian universe, and will be of great interest to students and scholars of the history and philosophy of science.

Speaker: Dan Dahlberg, University of Minnesota
Subject: Noise in Mesoscopic Magnetic Systems
4:40 pm:
Speaker: Melissa Eblen-Zayas, Carleton College
Subject: Redesigning an advanced lab course to promote experimental design

The advanced lab course can provide students with an opportunity to develop experimental design skills. However, students often struggle with the challenges and potential for failure that come with designing their own experiments. I will describe how we used results from the Colorado Learning Attitudes About Science Survey for Experimental Physics (E-CLASS) to explore student attitudes about experimental work in a course designed to promote the development of experimental design skills and how we have modified the course through the introduction of metacognitive activities in response to E-CLASS results.

Monday, April 3rd 2017
12:15 pm:
Speaker: Yong-Zhong Qian, UMN
Subject: Effects of eV-Scale Sterile Neutrinos on Supernova Explosion and Nucleosynthesis

We show that for the active-sterile flavor mixing parameters suggested by the reactor neutrino anomaly, substantial conversion between neutrinos (antineutrinos) of the electron and sterile flavors occurs in regions with electron fraction close to 1/3 near the core of an 8.8 solar mass supernova. Compared to the case without such conversion, the neutron-richness of the ejected material is enhanced to allow production of elements from Sr, Y, and Zr up to Cd in broad agreement with observations of the metal-poor star HD 122563. Active-sterile flavor conversion also strongly suppresses neutrino heating at times when it is important for the revival of the supernova shock. Our results suggest that simulations of supernova explosion and nucleosynthesis may be used to constrain active-sterile mixing parameters in combination with neutrino experiments and cosmological considerations.

Tuesday, April 4th 2017
12:20 pm:
There will be no seminar this week; group should attend Adam Kowalski's MIfA colloquium on Friday

Wednesday, April 5th 2017
1:30 pm:
There will be no seminar this week.
Subject: Paper Reading - "First measurement of muon-neutrino disappearance in NOvA"
Note change of room, for the rest of semester.
4:30 pm:
CM Journal Club in PAN 120
Speaker: Ruiqi Xing
Subject: The hunt for the pairing glue in the cuprates
Refreshments will be served.

To understand the microscopic mechanism of electrons forming cooper pairs in the high-Tc cuprates, in a recent(2016) paper[1], the authors made an attempt to quantitatively determine the pairing interactions for copper-oxide high-Tc superconductors through state-of-the-art laser-based angle-resolved photoemission(ARPES) measurements. I will talk about: (1)the key results they found (how they get the pairing interactions between electrons); (2) "loop current" theory, which they use to explain the experiments; how the idea
of marginal Fermi-liquid and loop current is developed by Chandra Varma et al. to explain phenomenon in cuprates; some concepts, some illustration through derivation (depending on the interest of audience) and current status of this theory.

Ref:
[1]Bok et al., "Quantitative determination of pairing interactions for high-temperature superconductivity in cuprates", Sci. Adv., 2,e150132(2016)
[2]Andrey V Chubukov, "The hunt for the pairing glue in the cuprates", http://www.condmatjournalclub.org/jccm-content/uploads/2016/03/JCCM_Mar_2016_01.pdf
[3]Vivek Aji, Arkady Shekhter, and C. M. Varma, "Theory of the coupling of quantum-critical fluctuations to fermions and d-wave superconductivity in cuprates", Phys. Rev. B 81, 064515(2010), etc.

Thursday, April 6th 2017
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
12:05 pm:
Speaker: Cody Carr
3:35 pm:
Speaker: Asimina Arvanitaki, Perimeter Institute
Subject: Particle Physics Beyond Colliders
Refreshments to be served outside Smith 100 after the colloquium.

When we think about Particle physics the first thing that comes to mind is colliders and high energies. Recently there have been several proposals of low-energy precision experiments that can also look for new particles, new forces, and the Dark Matter of the Universe in a way that is complementary to collider searches. In this talk, I propose two different experiments that search for a type of Dark Matter naturally arising in String Theory. In String Theory fundamental constants, such as the electron mass or charge, are determined by fields known as moduli. When these fields are the Dark Matter of our Universe, they cause the fundamental constants to oscillate with a frequency set by the Dark Matter mass. For frequencies smaller than 1 Hz atomic clocks with their unprecedented sensitivity can pick up these oscillations. For higher frequencies above 1 kHz, Dark Matter can excite acoustic modes in resonant mass detectors originally designed to detect gravitational radiation from astrophysical sources. Both techniques extend searches for this type of Dark Matter by several orders of magnitude in the near future.

Faculty Host: Tony Gherghetta

Friday, April 7th 2017
11:15 am:
To be announced.
Speaker: Tianbai Cui, University of Minnesota
Subject: Gap oscillations in superconductors driven out of equilibrium
Speaker: Ely Kovetz (John Hopkins)
Subject: The LIGO Discovery and Primordial Black Hole Dark Matter

The LIGO observatory has recently reported several detections of gravitational waves from the coalescence of binary black holes. We consider the extraordinary possibility that the detected events involving heavier masses are mergers of primordial black holes making up the dark matter in the Universe. We will describe various ways of testing this proposition once more gravitational wave data is gathered, survey some of the existing constraints and present a novel probe of massive compact dark matter in the relevant mass range based on strong gravitational lensing of fast radio bursts. We will conclude with a summary of the observational prospects to test the proposed scenario over the next decade.

Speaker: Today's MIfA colloquium has been cancelled.

During solar and stellar flares, the majority of the radiated energy from the lower atmosphere escapes as white-light continuum emission in the near- ultraviolet and optical wavelength regimes. The spectral energy distribution of the white-light emission is important for assessing biomarkers in planetary atmospheres around M dwarfs and for constraining models of heating at the highest densities in flares. In this talk, I will discuss the properties of solar flares gleaned from recent IRIS data and review recent observations of M dwarf flares, including the hottest and most energetic that has been observed to date. Spectral observations and radiative-hydrodynamic modeling suggest that the white-light continuum and the chromospheric line flux in solar and stellar flares originate over two flaring layers in the lower-to-mid chromosphere. However, the fluxes of accelerated particles that are necessary to reproduce the observations are so high that the propagation of the particles to the lower atmosphere may be affected by beam instabilities. I will present our new prescription for modeling the electric pressure broadening in flare spectra, which will help resolve the problem of how the highest densities in the stellar atmosphere are heated during flares. Finally, I will speculate on aspects of habitability in the recently discovered planetary systems around the flare stars Proxima Centauri and TRAPPIST-1.

3:35 pm:
Subject: "Medical Materialities: Teaching, Feeding, and Healing the Body through Medical Humanities" - A Conversation with Barbara Troise Rioda and David Gentilcore
Refreshments served at 3:25 p.m.
Speaker: Carolyn Bishoff, Physics, Astronomy and Earth Sciences Librarian
Subject: Workshop on data management
4:40 pm:
Speaker: Anita Schuchardt, University of Minnesota
Subject: Enhancing Science Learning and Problem Solving through Mechanism Connected Mathematics

While integrating mathematics into science classrooms has long been part of the conversation in science education, students still struggle to solve quantitative problems across science disciplines. Traditionally, most mathematics use in the science classroom mathematics is for algorithmic calculation of a quantity or as a provided expression of a known scientific law or relationship. Often, in these uses of mathematics, the meaning and connection of the mathematical expression to the scientific phenomenon is lost to naïve learners. An instructional model will be presented that has students engage in the scientific practice of mathematical modeling by developing and refining of equations that connect the variables and functions in the mathematical expression to the entities and mechanisms in the scientific phenomenon. Effects on student learning and problem solving in the context of a unit in biology will be discussed.

Monday, April 10th 2017
12:15 pm:
Speaker: D'Ann Barker, UMN
Subject: Low Energy Background Model for CDMSlite

One trend in dark matter direct detection is the development of techniques which will lower experimental thresholds and achieve sensitivity to low-mass dark matter particles. In doing so, it is necessary to have an understanding of the low energy spectrum and the major background components. To understand this region for the Super Cryogenic Dark Matter Search (SuperCDMS), a variety of specialized low energy models have been simulated and compared against theoretical calculations and SuperCDMS data. An important application of this model is to the CDMS low ionization threshold experiment (CDMSlite). CDMSlite has reached world-leading sensitivities in the search for low-mass weakly interacting massive particle dark matter. The sensitivity of the current data can be improved by understanding and modeling the experimental backgrounds down to threshold. Development of the machinery for creating a low energy background model will also be useful in the future SuperCDMS SNOLAB experiment which will operate multiple high voltage detectors in a manner similar to CDMSlite.

Tuesday, April 11th 2017
12:20 pm:
Speaker: Dr. Andreas Keiling, Space Science Lab, UCB
Subject: Substorms in the Solar System and their Periodicity

Spacecraft observations have established that all magnetized planets in our solar system (Mercury, Earth, Jupiter, Saturn, Uranus, and Neptune) interact strongly with the solar wind and possess well-developed magnetotails. Magnetotails are the site of many dynamic processes critical to the transport of mass, momentum, energy, and magnetic flux. The great differences in solar wind conditions, planetary rotation rates, ionospheric conductivity, and physical dimensions from Mercury’s small magnetosphere to the giant magnetospheres of Jupiter and Saturn provide an outstanding opportunity to extend our understanding of the influence of these factors on magnetotail processes and structure. Among the many differences and similarities, in this presentation I will provide an (sketchy) overview of magnetospheric substorms, together with new results on substorm periodicity.

4:30 pm:
There will be no seminar this week.

Wednesday, April 12th 2017
1:25 pm:
Speaker: Mansour Shayegan, Princeton University
Subject: News from Princeton Flatlands: Probing Exotic Phases of Interacting 2D Systems

In selectively-doped semiconductor structures, the electrons are spatially separated from the dopant atoms to reduce scattering by the ionized impurities. Thanks to the reduced disorder and scattering, such “clean” structures provide nearly ideal 2D systems for studies of electron-electron interaction phenomena, especially at low temperatures and high perpendicular magnetic fields where the thermal and kinetic energies of the electrons are quenched. The dominant electron interaction leads to various fascinating and exotic ground states such as the fractional quantum Hall state, Wigner crystal, and anisotropic (stripe) phases.

In my talk I’ll discuss our latest results in probing the intriguing properties of some of these phases. For example, in high-quality GaAs 2D electrons, a stripe phase is observed in the excited (N = 1) Landau level when a parallel magnetic field (B||) is applied. The stripes are typically oriented perpendicular to the B|| direction. Our experimental data reveals how a periodic density modulation, induced by a surface strain grating from strips of negative electron-beam resist, competes against the B||-induced orientational order of the stripe phase. Even a minute (≪ 1%) imposed density modulation is sufficient to reorient the stripes along the direction of the surface grating, if its period matches the (expected) period of the intrinsic stripes. The data thus suggest that the parallel and perpendicular orientations of the stripes must be energetically very close. I will also present experimental data on other 2D systems, e.g., 2D holes in GaAs or 2D electrons confined to AlAs quantum wells.

Faculty Host: Michael Zudov
Speaker: Minh Nguyen, University of Minnesota
Subject: Neutral Naturalness at the LHC
4:30 pm:
CM Journal Club in PAN 120
Speaker: Konstantin Reich
Subject: Basics of Polymer Physics
Refreshments will be served.

Thursday, April 13th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Prof. Grant W Luxton, University of Minnesota, Dept. of Biochemistry, Molecular Biology and Biophysics
Subject: To be announced.
12:05 pm:
Speaker: Karl Young
3:35 pm:
Speaker: Mansour Shayegan, Princeton
Subject: Measurements of Composite Fermion Geometric Resonance
Refreshments to be served outside Smith 100 after the colloquium.

There has been a surge of recent interest in the physics of interacting, two-dimensional (2D) electrons in a large perpendicular magnetic field when they occupy a half-filled Landau level. The long ago proposed composite fermion (CF) picture, in which two magnetic flux quanta are bound to each electron to form a CF, explains many properties of the system. These include the compressible (metallic) behavior of the 2D system at filling factor ν = ½, the existence of a Fermi contour with a well-defined Fermi wave vector, and the presence of fractional quantum Hall states as the filling deviates from ν = ½. In this talk, I will highlight the results of several recent experiments that probe the presence and properties of CFs via measuring the geometric resonance of CFs’ cyclotron orbit diameter with the period of an imposed, unidirectional density modulation. The data reveal several important aspects: (1) An unexpected asymmetry of the CFs’ Fermi wave vector for filling factors smaller and larger than ν = ½, suggesting a subtle breaking of particle-hole symmetry. (2) Anisotropic Fermi contours for CFs that can be tuned by applying in-plane magnetic field or in-plane strain. The strain results are particularly intriguing as they imply that the CFs inherit a Fermi contour anisotropy from their (parent) zero-field particles through a simple relation. (3) I will also discuss a bilayer experiment where the geometric resonance of CFs in one layer is used to probe an electron Wigner solid in the other layer.

Faculty Host: Michael Zudov

Friday, April 14th 2017
11:15 am:
Speaker: Zewei Xiong, University of Minnesota
Subject: Collective oscillations of dense neutrino gas

We study collective two-flavor oscillations of an isotropic gas of monochromatic neutrinos and antineutrinos. We analytically solve for the eigenstates at fixed neutrino density and perform stability analyses of these states. We use the stable eigenstates to understand the flavor evolution of the dense neutrino gas above the proto-neutron star in a core-collapse supernova or above the accretion disk in a neutron-star merger.

Speaker: Zedong Yang
Subject: Spin-dependent transport in semiconductor nanowires with strong spin-orbit coupling
Speaker: Kevin Zhang (U. Michigan)
Subject: Covariant diagrams: a new approach to one-loop EFT matching

Matching a full theory onto an effective field theory (EFT) by integrating out heavy fields is often useful for connecting low-energy phenomenology to high-scale physics. I introduce a new formulation of one-loop matching in terms of "covariant diagrams," which, unlike conventional Feynman diagrams, preserve gauge covariance and thus simplify calculations. Starting from a set of simple rules, I will demonstrate the use of covariant diagrams with examples. I will also discuss an interesting universal structure of one-loop effective Lagrangians revealed by such calculations.

Speaker: Carl Ferkinhoff, Winona State
Subject: Far-infrared fine-structure line studies of early galaxies: Where are we? Where do we need to go?

This year marks the 42nd anniversary of the first far-infrared fine-structure line detection, the [OIII] 88 micron line, by the NASA Learjet in 1975. Additional pioneering work through the early 90’s revealed the astrophysical importance of the full suite of far-IR lines and demonstrated their power as probes of the physics conditions in the interstellar medium (ISM). While inaccessible from ground at their rest wavelengths, they begin falling into the short submillimeter telluric-windows (~200 to 500 μm) from high-z systems at z~1. Over the past one and half decades ISO, Herschel and now SOFIA have provided detailed studies of the lines in the local universe while ground based observations made the first detections of the lines from the early universe. These first detections in the high-z universe demonstrated the lines’ utility for studying high redshift systems. This includes the ability to constrain the size of star-forming regions, quantity of ionized gas, age of the starburst, and gas phase abundances to name a few. Now in the ALMA era, studies using the fine-structure lines have the potential to dramatically increase our understanding of early galaxies, both in their formation and evolution. Much work is required, however, to fully realize this potential. In this talk I will seek to answer two questions in regards to the far-IR fine-structure lines: Where are we and where do we need to go? In answering these questions, I will summarize the current state of fine-structure line studies—both locally and in the distant universe—while highlighting some of my recent work with ALMA and explaning the “[CII] deficit”. In the last part of the talk, I will discuss future multi-wavelength studies, including that ZINGRS Radio Survey, which will help realize the full scientific potential of the FIR fine-structure lines for studying the early universe.

3:35 pm:
Speaker: Jeremy Greene, Johns Hopkins University
Subject: "Innovation on the Reservation: Information Technology and Health Systems Research Among the Papago Tribe of Arizona, 1965-1980"
Refreshments served at 3:25 p.m.

In May of 1973, an unusual collaboration between the NASA, the Indian Health Service, and the Lockheed Missile and Space Company promised to transform the way that members of the Papago (now Tohono O’odham) Nation of Southern Arizona accessed modern medicine. Through a system of state-of the art microwave relays, slow-scan television links, and mobile health units, the residents of this vast reservation—roughly the size of the state of Connecticut—would access physicians remotely via telemedical encounters instead of traveling to distant hospitals. The STARPAHC (Space Technology Applied to Rural Papago Advanced Health Care) partnership lasted from 1973 to 1977, but its legacies continue today.

The mission of STARPAHC was twofold: first, to help NASA test out its new Integrated Medical and Behavioral Laboratory Measurement System for use in future manned space flight, second, to help the IHS assess the role of new technologies for providing care across a vast rural landscape. While other accounts have explored the role of STARPAHC as an early telemedical system, little has been written on how or why the Papago reservation became an experimental site for biomedical communication technologies. We argue that STARPAHC was not entirely unprecedented, and had roots in other Cold War investigations into the role of health technologies in domestic and international health policy. Well before NASA became involved on the Papago reservation, the IHS had designated the Papago reservation as a “population laboratory” for testing new communications technologies inpublic health and primary health care, and tribal leadership had likewise developed this role through engagements with other forms of prototype electronic medical technologies.

This paper explores the configuration of the Papago reservation as an experimental site whose value derived in part from the ability of stakeholders in the IHS, the Peace Corps, and NASA to generalize its terrain to stand in for any number of other Native American reservations, villages in Malawi, Liberia, and Korea, or extra-terrestrial landscapes, respectively, as a proving ground for health communications technologies. This talk, drawn largely from archival materials and published articles is part of a larger project on the uses of communications technologies to resolve disparities.

Speaker: Nancy Sims, Copyright Program Librarian
4:40 pm:
Speaker: Laura McCullough, UW-Stout

Women are under-represented at every level of physics above high school. At the highest levels of physics, women are particularly scarce. What are the main factors creating barriers for women in physics leadership? How do they compare to the barriers facing women in physics more generally?

Monday, April 17th 2017
12:15 pm:
Speaker: Terry J. Jones, UMN
Subject: Things That Go Bump In the Night

Gamma Ray, X-Ray, and fast radio bursts - Oh My! A potpourri of recent observations of transient events at cosmological distances.

Speaker: Valerie Domcke, APC - University of Paris
Subject: A cosmological B-L phase transition

Cosmic inflation is an impressively successful paradigm in our understanding of the early Universe. Its embedding into particle physics is however still an open question. In this talk, I will present a complete' particle physics model of inflation. Based on the implementation of D-term hybrid inflation in strongly coupled supersymmetric gauge theories, this setup overcomes all the usual problems of D-term hybrid inflation, including the consistent generation of an Fayet-Iliopoulos term in supergravity and the cosmic string problem. The D term may be associated with a gauged U(1)_B-L, so that the end of inflation spontaneously breaks B-L in the visible sector, setting the stage for neutrino mass generation and leptogenesis.

Tuesday, April 18th 2017
12:20 pm:
There will be no seminar this week.
4:30 pm:
There will be no seminar this week.

Wednesday, April 19th 2017
1:25 pm:
There will be no seminar this week.
3:35 pm:
Special Physics and Astronomy Colloquium in Moos Health Science Tower 2-650
Speaker: Arthur McDonald, Queen's University and Sudbury Neutrino Observatory
Subject: Neutrino and Dark Matter Experiments at SNOLAB
Note change of day and location this week only for Van Vleck Lecture -- Refreshments to be served after the colloquium.

The Sudbury Neutrino Observatory (SNO) was a 1,000 tonne heavy-water-based neutrino detector created 2 km underground in an active nickel mine near Sudbury, Canada. SNO studied neutrinos from 8B decay in the Sun by observing one neutrino reaction sensitive only to solar electron neutrinos and others sensitive to all active neutrino flavors. It found clear evidence for neutrino flavor change. This requires modification of the Standard Model for Elementary Particles and confirms solar model calculations with great accuracy. Future measurements at the expanded SNOLAB facility will search for Dark Matter particles thought to make up 26% of our Universe and neutrino-less double beta decay, a rare form of radioactivity that can tell us further fundamental properties of neutrinos. The lecture will provide a brief description of the science of SNO and the status and science to be addressed by SNOLAB experiments.

4:30 pm:
CM Journal Club in PAN 120
Speaker: No CM Journal Club This Week

Thursday, April 20th 2017
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
12:05 pm:
Speaker: Avery Garon and Bob Lysak
3:35 pm:
Speaker: Jingyang Zheng
Subject: Electronic Conduction in Free-Standing Silicon Nanocrystalline Thin Films
Faculty Host: Paul Crowell
7:00 pm:
Van Vleck Public Lecture in Ted Mann Concert Hall
Speaker: Arthur B. McDonald, Queen's University and Sudbury Neutrino Observatory
Subject: A Deeper Understanding of the Universe from 1.2 miles Underground

By going 1.2 miles underground and creating an ultra-clean laboratory it is possible to address some very fundamental questions about our Universe: How does the Sun burn?; What are the dark matter particles making up 27% of our Universe?; What are the properties of neutrinos, elusive particles that are one of the fundamental building blocks of nature?. With the Sudbury Neutrino Observatory (SNO) we were able to observe new properties of neutrinos that go beyond the Standard Model of Elementary Particles and also confirm that the models of how the Sun burns are very accurate. With the expanded laboratory SNOLAB we are welcoming the world in collaborative experiments that are looking for the properties of Dark Matter particles, seeking further properties of neutrinos and looking for neutrino signals from supernovae in our galaxy, from the Earth and from the Sun. The advantages created by the development of one of the lowest radioactivity laboratories in the world and the resulting fundamental science will be described.

Friday, April 21st 2017
11:15 am:
Speaker: Julia Bliss, TU Darmstadt, Institut fur Kernphysik
Subject:  Impact of astrophysical and nuclear physics uncertainties on the nucleosynthesis in neutrino-driven winds

After a successful core-collapse supernova a neutrino-driven wind develops from the nascent neutron star. Neutrino-driven winds are a possible astrophysical site for the synthesis of the lighter heavy elements (26 < Z < 47) which are associated to the r-process and at least one additional process. Despite the fast process in the last years the astrophysical and nuclear physics uncertainties are still relatively large. We study the impact of the astrophysical uncertainties on the nucleosynthesis in the wind and have a special focus on the formation of 92,94Mo and 96,98Ru. The Mo and Ru p-isotopes have raised interest because their nucleosynthesis origin in the solar system is a long lasting mystery. We present the necessary conditions for the synthesis of 92,94Mo and 96,98Ru and show whether the wind can explain their solar system abundances. Moreover, we show that (alpha,n) reactions are critical to redistribute matter in neutron-rich winds. In the absence of experiments most (alpha,n) reaction rates are calculated with statistical models, and thus contain some uncertainties. Our results show that (alpha,n) rate uncertainties are crucial for the abundances. Since the nucleosynthesis path is close to stability, individual critical reactions can be measured with new radioactive beam facilities in the near future.

11:15 am:
Speaker: Dr. Brian J. Anderson, Johns Hopkins University Applied Physics Lab
Subject: Field-aligned auroral current systems at Earth and Mercury: Implications for magnetic convection at Mercury

Birkeland currents are present at both Earth and Mercury and the differences in currents reflect fundamental differences in the convection dynamics of these systems. At Earth, the conductive ionosphere and the high altitude magnetosphere are linked with these currents through the Pedersen conductance which closes the currents in the ionosphere and through magnetospheric plasma that carries the Region 2 currents between the evening and morning sectors, shielding the inner magnetosphere from the convection potential. The currents reflect the convection of magnetic flux from the dayside, over the polar caps into the magnetotail, and subsequently sunward in the tail to the dayside. At Mercury, Birkeland currents close through the planet itself with at least half of the current reaching the core to close laterally at polar latitudes. There is no evidence of Region 2 currents at Mercury implying that the magnetosphere and planet itself are not shielded from the convection cycle and suggesting that the planet also participates in the return convection although how this is actually accomplished is not known.

Speaker: Ioannis Rousochatzakis, University of Minnesota
Subject: Microscopic tunneling description of the spin-1/2 kagome Heisenberg antiferromagnet
Speaker: CANCELLED
Speaker: Stephanie Juneau, NOAO; CEA-Saclay
Subject: Cosmic Hide-and-Seek with Supermassive Black Holes

Supermassive black holes - with masses of millions to billions of times that of the Sun - reside in the nuclei of galaxies. While black holes are not directly visible, surrounding material becomes extremely luminous before being accreted, creating telltale signatures of black hole activity. In turn, the amount of activity tells us about black hole growth, and energy injection back into the host galaxies. This so-called black hole feedback is thought to play a role in galaxy evolution. Black hole activity is normally detectable at a range of wavebands including high energy X-rays. However, in some extreme cases, the usual signatures are either absorbed or obscured by intervening material along the line-of-sight. I will start by reviewing the state of the art in terms of black hole obscuration, and highlight new findings from a multi-scale analysis of gas ionization and dynamics thanks to 3D spectroscopy with the MUSE instrument. I will conclude with a global view of black hole growth and feedback in galaxies, including major questions that remain open for new capabilities such as the James Webb Space Telescope (JWST), and large galaxy survey experiments such as DESI and Euclid.

3:35 pm:
Speaker: Kathryn Tabb, Columbia University
Subject: "The Precision Medicine Turn in Psychiatry: Some Epistemic Puzzles and an Ethical Concern”
Refreshments served at 3:25 p.m.

Recent methodological, financial, and rhetorical shifts by the National Institute of Mental Health (NIMH) reveal the Institute’s growing interest in funding basic science research over clinical research. The most dramatic adjustment has been the abandonment of the Diagnostic and Statistical Manual of Mental Disorders in favor of an alternative classification protocol for psychiatric research, the Research Domain Criteria (RDoC) framework. I begin by giving a history of this shift, noting that RDoC is only a part a larger embrace by biomedical psychiatry of what has been called the “precision medicine model,” a new paradigm for medical research that uses biomarkers to stratify patients into new categories for treatment purposes. This shift in nosological practice is being accompanied—for contingent rather than necessary reasons, I show—by a heightened interest in neuroscientific explanations. I argue that these two new epistemic virtues—precision and neurocentrism—give rise to new epistemic puzzles about psychiatric progress, especially about the sort of explanations and interventions that biomedical researchers are likely to find. I conclude by showing that answering these epistemic puzzles will be a necessary part of tackling what I see as an important ethical concern about precision psychiatry: that it favors future patients over present ones.

Panel on career options
4:40 pm:
There will be no seminar this week.

Monday, April 24th 2017
12:15 pm:
Speaker: Evan Skillman, UMN
Subject: Carbon

I will report on recent measurements of carbon abundances from optical recombination lines of star forming regions in the spiral galaxy M101 obtained with the Modular Double Spectrograph on the Large Binocular Telescope. These observations allow us to study the evolution of the relative abundance of carbon as a function of absolute abundance.

4:40 pm:
Speaker: Bryan Chem
Subject: Computational Studies of Defect Mediated Transport
Faculty Host: Paul Crowell

Tuesday, April 25th 2017
12:20 pm:
There will be no seminar this week.
4:30 pm:
There will be no seminar this week.

Wednesday, April 26th 2017
1:25 pm:
Speaker: Turan Birol, CEMS, University of Minnesota
Subject: Correlated Materials by Design

The process of materials design involves solving the inverse band structure problem to predict what stoichiometry and crystal structure give rise to desired properties. First principles methods, such as Density Functional Theory (DFT), are used extensively to predict/design novel materials, from ferroelectrics to high temperature superconductors. In this talk, I am going to discuss my materials design efforts using Dynamical Mean Field Theory (DFT+DMFT), which is the state of the art first principles method to approach on-site electronic correlations in transition metal systems. In particular, I am going to start with discussing a novel group of J=1/2 fluoro-iridates, and then move on to efforts of designing superior transparent conductors by taking advantage of the electronic correlations in the well known perovskite oxide strontium vanadate.

Faculty Host: Rafael Fernandes

Title: Charged Lepton Violation (theory paper)
Author: Andrea de Gouvea, Northwestern Physics Dept
Topics: Model Independent CLFV, Exotic Models and production at LHC

4:30 pm:
CM Journal Club in PAN 120
Subject: There will be no CM Journal club

Thursday, April 27th 2017
08:00 am:
Untitled in Physics
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Prof. Julius Lucks, Northwestern University
Subject: Uncovering How RNA Molecules ‘Make Decisions’ On the Fly: Towards Understanding and Engineering Cotranscriptional RNA Folding

RNAs are emerging as a powerful substrate for engineering gene expression and cellular behavior since they are now known to control almost all aspects of gene expression. As with all biomolecules, RNA function is intimately related to its structure, since RNA can adopt structures that selectively modulate gene expression. Central questions in biology and bioengineering then are: How do RNAs fold inside cells?; and How can we engineer these folds to control gene expression? In this talk, I will present our work at the interface of these two questions and share results that are beginning to uncover design principles for understanding natural RNAs and engineering RNAs for an array of applications.

I will start by presenting our work on engineering RNA molecular switches that control transcription. The desire to uncover design principles for engineering these RNAs motivates our development of SHAPE-Seq, a technology that couples chemical probing with next-generation sequencing and that helps characterize RNA structures on an ‘omics’ scale. I will then describe our exciting recent developments in using SHAPE-Seq to help break open one of the frontiers of RNA structure-function relationships by uncovering at nucleotide resolution how RNAs fold cotranscriptionally. Specifically I will highlight new data on uncovering the ligand-dependent folding pathways of riboswitches, and how we are beginning to use these datasets to computationally reconstruct cotranscriptional folding pathways. This new ability is allowing us to ask deep questions about how RNA molecules make regulatory decisions ‘on the fly’ during the dynamic process of transcription. By probing the fundamental processes of RNA folding and function, these studies are expected to greatly aid RNA engineering.

12:05 pm:
Speaker: Jett Priewe and Claudia Scarlata
1:00 pm:
Speaker: Jingnan Cai
Subject: Crystal Growth and Seebeck Coefficient Measurement of Hg1201
Faculty Host: Paul Crowell
3:35 pm:
Speaker: Adriano Fontana, National Institute for Astrophysics (Italy)
Subject: The Large Binocular Telescope from first stars to exoplanets: challenges and results.
Refreshments to be served outside Smith 100 after the colloquium.

Modern-day astrophysics is facing many outstanding scientific questions.
They include the nature of the first stars and galaxies, the physics of the assembly and evolution of massive galaxies, the constraints to dark matter and cosmological model, the demographics of exoplanets and the physics of planet formation.

Progress in these fields is often driven by technological developments. Thanks to a wealth of new instrumentation that will become available in the very next years, we expect to be able to address or to make substantial advances toward the solution of most of these problems.

Crucially, key new technologies in the optical domain involve the use of adaptive optics for ground based telescopes, of which the Large Binocular Telescope is a world-leader.

In my talk I will briefly illustrate some of the “big” scientific questions that are on the table - at least in my personal and biased view - and then present the new technologies and instrumentation -mostly of which developed at LBT - that promise to revolutionize the field in a decade, including some early results from LBT.

Faculty Host: Roberta Humphreys

Friday, April 28th 2017
11:15 am:
There will be no seminar this week.
Speaker: Sajna Hameed, University of Minnesota
Subject: Magnetic Order and Excitations in Y1-xLaxTiO3
Faculty Host: Martin Greven
Speaker: Antonio Delgado, (Notre Dame U.)
Subject: Searching for compressed spectra

I will present two scenarios where standard searches for SUSY at the LHC are not very efficient because the mass splitting between the LSP and the NLSP is small and therefore there is not a lot of MET in the events. I will then use different observables to be able to improve the reach of the LHC in this kind of situations.

Subject: No MIfA speaker this week. See the SPA colloquium April 27th
Adriano Fontana, Nat'l Institute for Astrophysics (Italy)
3:35 pm:
Speaker: Jessica Riskin, Stanford University
Subject: "How the Mouse Lost its Tail, Or, Lamarck's Dangerous Idea"
Refreshments served at 3:25 p.m.

The clockwork cosmos of early modern science was a passive and static thing, its shape imposed by an external designer, its movements originating outside itself. The classical mechanists of the seventeenth century evacuated force and agency from the cosmos, including, for the most part, from its living inhabitants, to the province of a supernatural Clockmaker. They thereby built a kind of supernaturalism into the very structure of modern science. But not everyone concurred in this banishment. From the late seventeenth century onward, a tradition of dissenters embraced the opposite principle, that agency -- a capacity to act, to be self-making and self-transforming -- was essential to nature, especially living nature. A crucial member of this dissenting, active-mechanist tradition was the French naturalist Jean-Baptiste Lamarck, professor of natural history at the Muséum national d’histoire naturelle in Paris. This paper examines his rigorously naturalist approach -- which naturalized rather than outsourced agency -- and its exile from the halls of mainstream science.

Lamarck was the leading author of two major, related ideas: first, the term “biology” and the idea of biology as a distinct science of life, and second, the idea of species-change, what we would now call “evolution,” but I will call it “transformism” to avoid reading aspects of later theories back into these early ideas about species-change. In 1802, Lamarck defined “biology” as one of three parts of “terrestrial physics,” the part comprehending everything to do with living bodies, especially their organization and its “tendency to create special organs.” In other words, the idea that living things composed and transformed themselves was central to this original definition of “biology.”

The paper will examine the political history of these conjoined ideas, transformism and a science devoted to its study, which carried with them an atmosphere of materialism, radicalism and anti-clericalism. This atmosphere became especially troubling toward the end of the nineteenth century to people such as the German Darwinist biologist August Weismann, who offered a definitive new interpretation of Darwinism that eliminated any whiff of Lamarckism. He and other neo-Darwinists were so successful that even today, Lamarck’s name is still in bad odor. His ideas themselves cannot tell us why; only their history can do that.

Co-sponsored with the Consortium for the Study of the Premodern World and the Anselm House.

3:35 pm:
Speaker: Vikram Nagarajan
Subject: Antiferromagnetic Excitations in Underdoped HgBa_2CuO_(4+delta)
Faculty Host: Paul Crowell
Group presentations #1
4:40 pm:
There will be no seminar this week.

Monday, May 1st 2017
12:15 pm:
Speaker: Micaela Bagley, UMN
Subject: A High Space Density of Luminous Lyman-alpha Emitters at z~6.5

I will present the results of a systematic search for Lyman-alpha emitters (LAEs) at 6 < z < 7.6 using the HST WFC3 Infrared Spectroscopic Parallel (WISP) Survey. Our survey covers a volume ~ 8x10^5 Mpc^3, comparable to many of the narrowband surveys despite their larger area coverage. We identify two LAEs at z ~ 6.4, which are among the brightest LAEs discovered at these redshifts. Taking advantage of the broad spectral coverage of WISP, we are able to rule out almost all lower-redshift contaminants. These LAEs reside in Mpc-scale ionized bubbles that allow the Ly-alpha photons to redshift out of resonance before encountering the neutral IGM. Based on the observed constraints, we conclude that the observed LAEs alone are not sufficient to ionize their surrounding bubbles.

12:20 pm:
Speaker: Jacob Freyermuth
Subject: Growth Optimization Studies and Measurement of the Cuprate Superconductor HgBaCaCuO
Faculty Host: Paul Crowell

Tuesday, May 2nd 2017
12:20 pm:
Speaker: Cindy Cattell, University of Minnesota
Subject: What new information can high frequency waves tell us about the July 2012 'Carrington' event? Preliminary results from STEREO
4:30 pm:
There will be no seminar this week.

Wednesday, May 3rd 2017
1:25 pm:
Speaker: Michael Levin, University of Chicago
Subject: Bulk-boundary correspondence for three dimensional topological phases

For certain classes of insulating materials, it is possible to derive a very precise connection between properties of the bulk and properties of the surface. A connection of this kind is known as a bulk-boundary correspondence. While such correspondences can be very useful, unfortunately the only cases where they are understood in generality involve either non-interacting or low-dimensional systems. In this talk, I will discuss progress on the bulk-boundary correspondence for a large class of three-dimensional, interacting systems. Specifically, the systems I will discuss are known as symmetry-protected topological phases and can be thought of as generalizations of topological insulators and superconductors.

Faculty Host: Oriol T. Valls
To be announced.
3:35 pm:
Speaker: Michael Hank
Subject: Detecting Very-High-Energy Gamma Ray Sources with Machine-Learning
Faculty Host: Paul Crowell
4:30 pm:
CM Journal Club in PAN 120
Speaker: Daniel Shaffer, University of Minnesota
Subject: Topological Superconductor
Refreshments will be served.

References:
1.Masatoshi Sato, Yoichi Ando, 'Topological superconductors: a review', https://arxiv.org/abs/1608.03395
2.Barry Simon, 'Holonomy, the Quantum Adiabatic Theorem, and Berry's Phase
', https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.51.2167
3.Edward Witten, 'Three Lectures On Topological Phases Of Matter', https://arxiv.org/abs/1510.07698

Thursday, May 4th 2017

8:45 am REGISTRATION
Keller Hall
200 Union Street SE
Room 3-180

8:55 am Welcome and opening comments
Boris Shklovskii
FTPI, University of Minnesota

9:00 am Role of Surface Chemistry on Charge Carrier Transport in Quantum Dot Solids
Cherie Kagan
University of Pennsylvania

9:45 am Charge transport in nanocrystal arrays: a chemist’s perspective
Dmitri Talapin
University of Chicago

10:30 am COFFEE BREAK

11:00 am Physics of mid-infrared detection with colloidal quantum dots
Philippe Guyot-Sionnest
University of Chicago

11:45 am Quantum-Dot Spasers and Plasmonic Amplifiers
David Norris
ETH Zurich

12:30 pm LUNCH BREAK

2:00 pm Early time photoconductance dynamics in quantum-dot solids probed by ultrafast photocurrent spectroscopy
Victor Klimov
Los Alamos National Laboratory

2:45 pm Field-Induced Doping of Colloidal Nanocrystal Assemblies: Traps, Transport & Utilizations
Satria Zulkarnaen Bisri
RIKEN Center for Emergent Matter Science

3:30 pm COFFEE BREAK & POSTER SESSION

5:30 pm Workshop ends for the day

10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
11:00 am:
Subject: Impact of nematicity in the optical response of iron-based superconductors
Faculty Host: Rafael Fernandes
12:05 pm:
Speaker: Vihang Mehta and Michael Rutkowski, Stockholm University
3:35 pm:
Speaker: Henry Sobel, University of California, Irvine
Subject: The Study of Neutrinos and Nucleon Decay in Japan
Student Awards will be presented at the start of Colloquium. Refreshments to be served outside Smith 100 after the colloquium.

The study of neutrinos and nucleon decay has along history in Japan beginning with the Kamiokande experiment in the 1980’s and continuing today with Super-Kamiokande and the T2K long baseline experiment. I will describe the sequence of experiments, their major results, and the current planning for the next stage of experiments with Super-Kamiokande-Gd, Hyper-Kamiokande and T2K-II.

Faculty Host: Yong-Zhong Qian

Friday, May 5th 2017

9:00 am Charge and energy transport in films of touching nanocrystals
Konstantin Reich
FTPI, University of Minnesota

9:45 am COFFEE BREAK

10:30 am Electron and exciton transport in plasma-produced, disordered nanocrystal films
Uwe Kortshagen
University of Minnesota

11:15 am Matrix engineering for efficient charge transport in PbX quantum dot solids
Matt Law
University of California, Irvine

12:00 pm LUNCH BREAK

2:00 pm Bright and dark exciton transfer in quantum dot arrays
Anna Rodina
Ioffe Institute, St. Petersburg, Russia

2:45 pm Visualizing Current Flow at the Mesoscale in Assemblies of Touching
Semiconducting Nanocrystals
Elijah Thimsen
Washington University in St. Louis

3:30 pm COFFEE BREAK

4:15 pm Photogeneration, diffusion and decay of charge carriers in quantum-dot solids
Arjan Houtepen
Delft University of Technology, The Netherlands

5:00 pm Workshop ends for the day

11:15 am:
There will be no seminar this week.
Speaker: Gino Graziano, University of Minnesota
Subject:  Topological Josephson Devices in InAs/GaSb Quantum Wells
Speaker: Andrew Matas (University of Minnesota)
Subject: Aspects of Massive Gravity

I will review the motivation for and construction of a theory of Lorentz-invariant massive gravity which is free of the Boulware-Deser ghost. After giving an overview of observational constraints on massive gravity, I will describe in more detail spherically symmetric solutions which exhibit the Vainshtein screening mechanism, which is required to avoid the van Dam-Veltman-Zakharov discontinuity. I will show how these solutions can be used to study fifth force effects in the solar system, as well as scalar radiation from binary pulsars.

Subject: MXP Poster Session

Poster session for the PHYS 4052 projects class in the atrium of PAN from 2:30 to 3:20.

Please come on by and check out all the excellent projects the students have been doing.

Subject: The Spectral Signatures of Deep Atmospheric Heating in Solar and Stellar Flares

During solar and stellar flares, the majority of the radiated energy from the lower atmosphere escapes as white-light continuum emission in the near-ultraviolet and optical wavelength regimes. The spectral energy distribution of the white-light emission is important for assessing biomarkers in planetary atmospheres around M dwarfs and for constraining models of heating at the highest densities in flares. In this talk, I will discuss the properties of solar flares gleaned from recent IRIS data and review recent observations of M dwarf flares, including the hottest and most energetic that has been observed to date. Spectral observations and radiative-hydrodynamic modeling suggest that the white-light continuum and the chromospheric line flux in solar and stellar flares originate over two flaring layers in the lower-to-mid chromosphere. However, the fluxes of accelerated particles that are necessary to reproduce the observations are so high that the propagation of the particles to the lower atmosphere may be affected by beam instabilities. I will present our new prescription for modeling the electric pressure broadening in flare spectra, which will help resolve the problem of how the highest densities in the stellar atmosphere are heated during flares. Finally, I will speculate on aspects of habitability in the recently discovered planetary systems around the flare stars Proxima Centauri and TRAPPIST-1.

3:35 pm:
There will be no colloquium this week.
Group presentations #2
4:40 pm:
There will be no seminar this week.

Saturday, May 6th 2017

9:00 am Symmetry breaking induced activation of the nanocrystal photoluminescence
Alexander Efros
Navy Research Laboratory

9:45 am Disorder, Nonequilibrium Transport, and the Origin of Deep Traps in Quantum Dot Solids
William Tisdale
Massachusetts Institute of Technology

10:30 am COFFEE BREAK

11:00 am Tracking the Energy Flow on Nanoscale via Sample-Transmitted Excitation Photoluminescence (STEP) Spectroscopy
Mikhail Zamkov
Bowling Green State University

11:45 am Electronic Transport Phenomena in Composite Nanocrystalline/amorphous and Free-Standing Nanocrystalline Thin Films
James Kakalios
University of Minnesota

12:30 pm Workshop ends.

Thursday, May 11th 2017
12:15 pm:
Thesis Defense in PAN 110
Speaker: Andy Julin, University of Minnesota
Subject: Measurement of DD Decays from the psi(3770) Resonance
This is the public portion of Mr. Julin's thesis defense. His advisor is Ron Poling.

We measure the production cross section of e^+ e^− → ψ(3770) → DD near the peak of the ψ(3770) resonance. The (69.80 ± 0.03) pb^−1 of e^+ e^− annihilation data used were collected in 2010 over a center-of-mass energy range of 3.735 GeV to 3.870 GeV. From previously observed e^+ e^− → DD cross section measurements, this shape cannot be explained by a single Breit-Wigner. Instead, in this analysis we fitted the cross section by including interference effects from non-resonant DD production, and measured the mass and width of the ψ(3770) more precisely than previous results.

Friday, May 12th 2017
11:00 am:
Thesis Defense in PAN 110
Speaker: Xiaoyu Wang, University of Minnesota
Subject: Interplay between charge, spin and superconducting properties in copper-based and iron-based superconductors.
This is the public portion of Mr. Wang's thesis defense. His advisor is Rafael Fernandes.

Saturday, May 13th 2017
3:35 pm:

Wednesday, May 17th 2017
08:55 am:
"Olivefest: Astroparticle Physics Looking Forward" workshop in in Humphrey School of Public Affairs - Cowles Auditorium

8:45 AM
Registration

8:55 AM
Welcome and Opening Remarks

9:00 AM
Mark Srednicki
University of California, Santa Barbara
Dark Matter: a Historical Perspective

9:30 AM
Howie Baer
University of Oklahoma
What does it take to discover or falsify weak scale SUSY?

10:00 AM
Pearl Sandick
University of Utah
A galaxy and it's dark matter profile: a story of enhanced annihilations

10:30 AM
COFFEE BREAK

11:00 AM
Carlos Munoz
On a reinterpretation of the Higgs field in supersymmetry and a proposal for new quarks

11:30 AM
Natsumi Nagata
The University of Tokyo
Probing metastable gluinos at the LHC

12:00 PM
LUNCH BREAK

2:00 PM
Maxim Pospelov
University of Victoria
Light particle solutions to the lithium problem in cosmology

2:30 PM
Brian D. Fields
University of Illinois, Urbana-Champaign
A Bitter Pill? The Primordial Lithium Problem

3:00 PM
Jean-Philippe Uzan
Institut d'Astrophysique de Paris
Gravitation: constants, a wall and some waves

3:30 PM
COFFEE BREAK

4:00 PM
Alon Faraggi
University of Liverpool
Olive Groves in the Garden of Eden and other Dark Middle Eastern delights

4:30 PM
Michael Barnett
Lawrence Berkeley National Laboratory
Bringing Astrophysics and Cosmology to the Particle Data Book

5:00 PM
Kimmo Kainulainen
Baryogenesis from Dark Sector

Thursday, May 18th 2017
09:00 am:
"Olivefest: Astroparticle Physics Looking Forward" workshop in in Humphrey School of Public Affairs - Cowles Auditorium

9:00 AM
John Ellis
Kings College London
Keith’s dark side (and some others)

9:30 AM
Sven Heinemeyer
IFT/IFCA (CSIC)
Preferred DM Scenarios in SUSY Theories

10:00 AM
Feng Luo
IPMU
QCD bound-state effect on dark matter relic abundance

10:30 AM
COFFEE BREAK

11:00 AM
Dimitri Nanopoulos
Texas A&M University
Keith Inflated

11:30 AM
Marcos Garcia Garcia
Rice University
Toward a stochastic description of reheating

12:00 PM
Rocky Kolb
University of Chicago
Particle Creation in the Expanding Universe

12:30 PM
LUNCH BREAK

2:00 PM
Joe Silk
Johns Hopkins University
The Limits of Cosmology

2:30 PM
Elisabeth Vangioni
Institut d'Astrophysique de Paris
From local chemical evolution to cosmic chemical evolution

3:00 PM
Evan Skillman
University of Minnesota
Observational Constraints on the Primordial Helium Abundance

3:30 PM
COFFEE BREAK

4:00 PM
Renata Kallosh
Stanford University
Alpha-attractors and B-mode targets

4:30 PM
Emilian Dudas
Center de Physique Theorique
Protection of scalar masses from higher dimensions

Friday, May 19th 2017
09:00 am:
"Olivefest: Astroparticle Physics Looking Forward" workshop in in Humphrey School of Public Affairs - Cowles Auditorium

9:00 AM
Andrei Linde
Stanford University
Large field inflation: recent progress and observational predictions

9:30 AM
Jason Evans
Low-Scale D-term Inflation and the Relaxion

10:00 AM
Kin-Wang Ng
Ultra-light axion dark matter and CMB B-mode polarization

10:30 AM
COFFEE BREAK

11:00 AM
Stefano Profumo
University of California, Santa Cruz
Astrophysical Searches for Dark Matter: A Status Report

11:30 AM
Vassilis Spanos
University of Athens
Gravitino dark matter

12:00 PM
Yann Mambrini
Universite Paris-Sud
A minimal model of gravitino dark matter

12:30 PM
LUNCH BREAK

2:00 PM
Grant Mathews
Notre Dame University
Constraints on superstrings, inflation, and extra dimensions from the CMB and big bang nucleosynthesis

2:30 PM
Katherine Freese
University of Michigan
Dark Stars: Dark Matter Annihilation can power the first stars

3:00 PM
Pierre Salati
LAPth & Universitat Savoie Mont Blanc
Antimatter cosmic rays: recent results with the semi-analytic approach

3:30 PM
COFFEE BREAK

4:00 PM
Masahiro Ibe
IPMU
Dark Matter Candidates in a Heavy QCD Axion Model

4:30 PM
Nemanja Kaloper
University of California, Davis
TBA

12:20 pm:
Special Seminar in PAN 110
Speaker: Yuan Wan, Perimeter Institute for Theoretical Physics
Subject: Generation and control of non-equilibrium landscape in a frustrated magnet

Geometrically frustrated magnets often possess accidentally degenerate ground states at zero temperature. At low temperature, thermal fluctuations lift the accidental degeneracy and stabilize ground states with maximal entropy. This phenomenon, known as “order by disorder”, underlines the fluctuation contribution to the free energy landscape in frustrated magnets.

In this talk, I show that such free energy landscape may be controlled in a non-equilibrium setting. This is owing to the fact that the slow motion along the ground state manifold is governed by the fast modes deviating away from the manifold. I will demonstrate this idea on a model system, namely the classical pyrochlore XY antiferromagnet, where exciting the fast modes produces a tuneable effective free energy landscape with minima located at thermodynamically unstable states. I will also discuss the implications on pyrochlore antiferromagnet materials such as Er2Ti2O7 and NaCaCo2F7.

Faculty Host: Natalia Perkins
1:00 pm:
Speaker: Tadayuki Takahashi, JAX/ISAS and the University of Tokyo
Subject: New hard X-ray and gamma-ray detectors for future high energy astronomy missions

This seminar will be of interest to anyone interested in semiconductor detectors, high-energy astronomy, space physics, and other X-ray measurements.

Monday, May 22nd 2017
08:00 am:

Monday, May 29th 2017
08:00 am:

Tuesday, June 6th 2017
09:00 am:

Friday, June 9th 2017

Monday, June 12th 2017
08:00 am:

Wednesday, June 14th 2017
2:00 pm:
Thesis Defense in PAN 110
Speaker: Mehdi Lamee, University of Minnesota
Subject: The Ionized Intergalactic Medium and its Influence on Galaxies and Galaxy Clusters
This is the public portion of Mr. Lamee's PhD examination, advisor L. Rudnick

Friday, June 16th 2017
10:30 am:
Thesis Defense in PAN 210
Speaker: Jiaming Zheng, University of Minnesota
Subject: Dark Matter Models in Non-Supersymmetric SO(10) Unification Theories
This is the public portion of Mr. Zheng's thesis defense. His advisor is Keith Olive.

We studied systematically non-supersymmetric SO(10) models that contain dark matter candidates. The stability of the dark matter particle is guaranteed by a remnant Z_2 subgroup of SO(10). We build models base on various dark matter production mechanisms and check them against several phenomenological constraints, such as the light neutrino masses, direct detection bounds on dark matter candidates and the proton decay lifetime. The requirement of gauge coupling unification offers a severe constraint on the model building. We also demonstrate that the vacuum stability problem of the Standard Model can be evaded by one of our scalar dark matter models.

Saturday, June 24th 2017
8:30 pm:
Universe in the Park in Nerstrand Big Woods State Park
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Tuesday, June 27th 2017
12:30 pm:
Speaker: O. Sushkov, University of New South Wales
Subject: Quantum magnetic criticality in 3D

In this talk, Oleg will discuss:

(i) the p-B-T phase diagram.
(ii) logarithmic decay of the coupling constant ("asymptotic freedom").
(iii)Narrow paramagnons in magnetically disordered regime.
(iv) Bose condensation.
(v) Higgs mode and its decay width in different regimes.
(vi) Comparison with data on TlCuCl3.

Faculty Host: Andrey Chubukov

Saturday, July 1st 2017
8:30 pm:
Universe in the Park in William O'Brien State park
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Tuesday, July 4th 2017

Friday, July 7th 2017
11:00 am:
Thesis Defense in PAN 110
Speaker: Yuriy Sizyuk, University of Minnesota
Subject:  4d and 5d compounds as the new frontier of the anisotropic spin physics
This is the public portion of Mr. Sizyuk's thesis defense. His advisor is Natalia Perkins.

My talk will be on the strong spin-orbit coupling as a source of heavily anisotropic magnetic Hamiltonians in 4d and 5d compounds, most notably iridates and RuCl3. I will discuss the derivation of the anisotropic Hamiltonians from microscopic parameters, and the competition and cooperation of different interactions that lead to the complex magnetic states in iridates and RuCl3.

Saturday, July 8th 2017
8:30 pm:
Universe in the Park in Afton State Park
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Monday, July 10th 2017
08:00 am:

Thursday, July 13th 2017
09:30 am:
Thesis Defense in PAN 110
Speaker: Samuel Ducatman, University of Minnesota
Subject: Magnetic Excitations of Hyperhoneycomb beta-Lithium Iridate.
This is the public portion of Mr. Ducatman's thesis defense. His advisor is Natalia Perkins.

Friday, July 14th 2017
2:30 pm:
Thesis Defense in 110 PAN
Speaker: Han Fu, University of Minnesota
Subject: Electron transport in SrTiO3 accumulation layers and semiconductor nanocrystal films
This is the public portion of Ms. Fu's Thesis Defense. Her advisor is Boris Shklovskii

We start from the low temperature conductivity of electron accumulation layers induced by the very strong electric fi eld at the surface of STO sample. Due to the strongly nonlinear lattice dielectric response, the three-dimensional density of electrons n(z) in such a layer decays with the distance from the surface z very slowly as n(z) ~1/z^{12/7}. We show that when the mobility is limited by the surface scattering, the contribution of such a tail to the conductivity diverges at large z because of growing time electrons need to reach the surface. We explore truncation of this divergence by the fi nite sample width, by the bulk scattering rate, by the back gate voltage, or by the crossover to the bulk linear dielectric response with the dielectric constant \kappa. As a result we arrive at the anomalously large mobility, which depends not only on the rate of the surface scattering, but also on the physics of truncation. Similar anomalous behavior is found for the Hall factor, the magnetoresistance, and the thermopower.

Finally, we switch to the study of NC films. We focus on the variable-range hopping of electrons in semiconductor NC fi lms below the critical doping concentration nc at which fi lms become metallic. The hopping conductivity is then described by the Efros-Shklovskii law which depends on the localization length of electrons. We study how the localization length grows with the doping concentration n in the film of touching NCs. For that we calculate the electron transfer matrix element t(n) between neighboring NCs when NCs touch by small facets. We use the ratio of t(n) to the disorder-induced NC level dispersion to fi nd the localization length of electrons due to the multi-step elastic co-tunneling process.

8:00 pm:
Universe in the Park in Dodge Nature Center
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Saturday, July 15th 2017
8:30 pm:
Universe in the Park in Lowry Nature Center
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Friday, July 21st 2017
2:00 pm:
Thesis Defense in PAN 110
Speaker: Chun Chen, University of Minnesota
Subject: A New Type of Many-Body Majorana Zero Modes in Fermionic Flux Ladder Model
This is the public portion of Mr. Chen's thesis defense. His advisor is Fiona Burnell.

One-dimensional topological superconductors and superfluids are typically classified and understood through Bogoliubov–de Gennes mean-field Hamiltonians. This raises the question of whether they can exist in truly one-dimensional systems where particle number is conserved. We discuss a new mechanism by which Majorana zero modes can arise in a number-conserving Fermi ladder. This interaction-enabled topological phase is protected by a unitary symmetry that is not related to any microscopic fermion-parity symmetry.

8:30 pm:
Universe in the Park in Cedar Creek Ecosystem Science Reserve
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Saturday, July 29th 2017
8:30 pm:
Universe in the Park in Afton State Park
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Friday, August 4th 2017
08:00 am:
Untitled in Physics
12:15 pm:
No Seminar, Labor Day
8:30 pm:
Universe in the Park in Mille Lacs kathio State Park
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Saturday, August 5th 2017
8:30 pm:
Universe in the Park in Father Hennepin State Park
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Friday, August 11th 2017
8:30 pm:
Universe in the Park in William O'Brien State park
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Saturday, August 12th 2017
8:30 pm:
Universe in the Park in Lake Maria State Park
Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing. This event is free and open to the public, though a vehicle permit is usually required to enter state parks.

Sunday, August 13th 2017
12:00 pm:
Pre-eclipse Block Party in Outdoor space between Physics and Nanotechnology Building and Akerman Hall
Speaker: James Flaten, Aerospace Engineering and Mechanics; Lindsay Glesener, School of Physics and Astronomy
Subject: "Live-streaming the Solar Eclipse from the Stratosphere," and "A Rare Look at the Sun's Corona."

1) (Flaten) NASA’s Space Grant Consortia from 30 states are fielding teams of college students to develop light-weight video-telemetry systems to live stream the view of the shadow of the Moon from the stratosphere. Over 50 ballooning teams are preparing to fly into the path of totality from Oregon all the way to South Carolina. The U of M team will show off their flight units and ground station hardware and talk about their preparations to participate in this nationwide project.

2) (Glesener) Solar eclipses are beautiful and fascinating events, and they also offer rare opportunities to study the elusive corona -- the outermost layer of the Sun's atmosphere. With a temperature hundreds of times greater than that of the Sun's surface, the mysterious corona is governed by strong magnetic fields that control all structure and motion. Explore the fascinating nature of the outer layers of the Sun and learn how you can contribute to solar science while you view the eclipse!

Friday, August 18th 2017

Monday, August 28th 2017
2:00 pm:
Thesis Defense in Akerman 225
Speaker: Quentin Ebner, University of Minnesota
Subject: The Effects of Alloy Disorder and Density on Non-Equilibrium Transport in Two-Dimensional Electron Gases

Tuesday, August 29th 2017
12:15 pm:
Thesis Defense in Tate 301-20
Speaker: Melanie Galloway, University of Minnesota
Subject: Morphology is a Link to the Past: examining formative and secular galactic evolution through morphology
This is the public portion of Ms. Galloway's thesis defense. Her advisor is Lucy Fortson

Monday, September 4th 2017
08:00 am:
12:15 pm:
No Seminar, Labor Day

Tuesday, September 5th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Nicole Vilmer, LESIA, Paris Observatory
Subject: Radio Diagnostics of Energetic Electron Beams and of Magnetic Fields in the Corona

RADIO DIAGNOSTICS OF ENERGETIC ELECTRON BEAMS AND OF MAGNETIC FIELDS IN THE CORONA

Faculty Host: Lindsay Glesener

Wednesday, September 6th 2017
1:30 pm:
There will be no seminar this week.
3:35 pm:
Planning meeting
4:30 pm:
CM Journal Club in PAN 120
No journal club this week.

Thursday, September 7th 2017
09:00 am:
Thesis Defense in Tate 301-20
Speaker: Cheng-Hsien Li, University of Minnesota
Subject: Astrophysics and Physics of Neutrino Detection
This is the public portion of Mr. Li's thesis defense. His Advisor is Yongzhong Qian.

A galactic core-collapse supernova is a powerful neutrino source of which the signals can be picked up by a water Cherenkov detector on the Earth. From an astrophysical point of view, the signals reveal the dynamics of core-collapse supernova explosion and the subsequent cooling of a proto-neutron star (PNS). In this regard, we compare the neutrino emission profiles from the recent 1D hydrodynamics simulation by Mirizzi et al. (2016) with the historical SN1987A data through a statistical goodness-of-fit test. Such test reveals the tension between the data and rapid PNS cooling prescribed by the convection treatment employed in the simulation. The implications will be discussed. From a quantum-mechanical point of view, on the other hand, the supernova neutrino flux is so intensive such that a huge degree of wave-packet overlap is estimated. Such overlap may give rise to an interference effect known as the Hanbury Brown and Twiss (HBT) effect. We derive the solution for a 3D Gaussian wave packet and, with such solution, the joint-detection probability. We demonstrate that an observable interference occurs if the joint-detection were to render the two detected neutrinos in the same phase space cell. Upon further examination, however, we conclude that such effect is difficult to observe from neutrinos in practical experimental settings.

10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
Speaker: Kazunori (Bish) Ishibashi, Nagoya U.
Subject: A survival guide for a PhD student

When you graduate, you will not have a job in academia.” This is the message that I received upon entering the University of Minnesota in 1994. This rings true in today's world, perhaps more so. Here I will share stories about how I survived grad school, fierce competition in the job market, and ended up being a tenured faculty at the university, while making some cool scientific discoveries along the way in X ray astronomy, the "little Homunculus" of eta Car, and development of a space based observatory. From this “unusual” journal club talk, I hope that grad students can pick up some tips to survive – or better yet, “to thrive” – in whatever they choose to do with their lives after grad school.

Faculty Host: Roberta Humphreys
3:35 pm:
There will be no colloquium this week.

Friday, September 8th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
12:20 pm:
Speaker: Thais Trevisan, University of Minnesota
Subject: Impact of disorder on the superconducting transition temperature near a Lifshitz transition: application to the phase diagram of SrTiO3
Speaker: Bharat Ratra (Kansas State U.)
Subject: Cosmological Seed Magnetic Field from Inflation

A cosmological magnetic field of nG strength on Mpc length scales could be the seed magnetic field needed to explain observed few microG large-scale galactic magnetic fields. I first briefly review the observational and theoretical motivations for such a seed field, two galactic magnetic field amplification models, and some non-inflationary seed field generation scenarios. I then discuss an inflation magnetic field generation model. I conclude by mentioning possible extensions of this model as well as potentially observable consequences.

There is no colloquium this week.
3:35 pm:
Speaker: Dr. Jennifer Alexander, History of Science and Technology - University of Minnesota
Subject: Technology, religion, and postwar debates about the order of creation: how the history of science and religion has led us into error in analyzing technology and religion
Refreshments served at 3:15 p.m.

Technology and religion in history can no longer fruitfully be analyzed within current parameters, which have been set by debates about science and religion. This talk uses debates about technology, theology, and the order of creation at the post-war forming of the World Council of Churches to illustrate that questions about science and religion were marginal, and that they yielded conservative political perspectives on the rebuilding of war-torn Europe. The talk comments on Peter Harrison's Gifford Lectures of 2011, recently published as The Territories of Science and Religion (Chicago, 2015), and on Harrison's respondents, who have suggested using the World Council of Churches and its emphasis on technology and practical projects as a way to rebuild the notion of a dialogue between science and religion.

Speaker: Lindsay Glesener, University of Minnesota
Subject: Course Introduction

Monday, September 11th 2017
12:15 pm:
Speaker: Kelley Hess, Department of Astronomy, University of Cape Town
Subject: Galaxy groups and the assembly of large scale structure

Galaxy groups are the most common environment, and the site where the majority of galaxy evolution occurs. Gas processing--through tidal interactions, ram pressure stripping, viscous stripping, etc--depletes the cold gas, shuts down star formation, and contributes to the build-up of the warm-hot intragroup medium that is sometimes detected in X-rays. As groups accrete more galaxies, the groups themselves become increasingly poor in neutral atomic hydrogen (HI), and more cluster-like. I will present the results of stacking ROSAT All-Sky Survey images for a large sample of groups for which we have complementary HI data from the ALFALFA HI survey in an attempt to detect the build-up of the WHIM in intermediate mass groups M>10^13 M_Sun, where we begin to see the impact of the group environment on the HI content of their member galaxies.

Understanding pre-processing in galaxy groups is in-turn critical to understanding the galaxy cluster population, and in the second half I will present two nearby clusters where we have used wide-field observations in radio, infrared, optical, and X-ray to identify substructure and used the galaxies' kinematics, HI gas, stellar, and hot gas properties to deconstruct the cluster assembly history.

Faculty Host: Liliya L.R. Williams

Tuesday, September 12th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Andrew Inglis, NASA/Goddard
Subject: Characterizing discrete power in solar flares and the magnetosphere using the AFINO algorithm.

The search for discrete power in timeseries is an important goal throughout many areas of Heliophysics, from the physics of solar flares to understanding waves in the Earth's magnetosphere. The AFINO (Automated Flare Inference of Oscillations) code is a novel algorithm which was originally developed to search for periodic signatures in solar flares using a model comparison technique. We present the original results of AFINO, which was used to carry out a large-scale search for quasi-periodic pulsations in 675 M- and X-class flares observed by GOES in 1-8 Å soft X-rays between 2011 February 1 and 2015 December 31. For the first time, we are able to estimate the occurrence rate of periodic signatures in flares, their characteristic periods, and their dependence on other flare parameters.

Since then, we have adapted AFINO in order to search for regions of discrete and broadband wave power in the Earth's magnetosphere, in particular to search for ULF waves. ULF waves play a fundamental role in the dynamics of the inner-magnetosphere during geomagnetic storms and in particular the dynamics of energetic electron in the outer radiation belt. Here, we show the results of AFINO applied to GOES magnetometer data, and also to a moderate geomagnetic storm observed by MMS. By analyzing multiple magnetic field components simultaneously we can determine which types of ULF wave modes dominate at different L-shells, and their typical properties. These results can be combined with a novel method utilizing the close separation of the MMS spacecraft and cross-phase between wave signals to estimate the ULF wave azimuthal wave number m.

Faculty Host: Lindsay Glesener
4:30 pm:
To be announced.

Wednesday, September 13th 2017
Speaker: Xinxin Cai
Subject: Magnetoresistance oscillations and the half-flux quantum state in mesoscopic Sr2RuO4

Spin-triplet superconductor Sr2RuO4 was predicted to support exotic objects such as half-quantum vortices, which carry a magnetic flux half of the flux quantum Phi_0=hc/2e. We report electrical transport measurements on micron-sized, doubly connected cylinders of Sr2RuO4 single crystals with the cylinder axis along the c axis. Large amplitude magnetoresistance oscillations were observed, revealing unconventional Little-Parks effect dominated by vortex crossing. The free energy barrier that controls the vortex crossing was modulated by the magnetic flux enclosed in the cylinder, an in-plane field, measurement current, and factors related to sample geometry. Distinct features on magnetoresistance peaks were found consistent with the emergence of the half-quantum state in this material, only in samples for which the vortex crossing is confined at specific parts of the sample.

3:35 pm:
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 120
Speaker: To be announced.

Thursday, September 14th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Jared Hennen, University of Minnesota
Subject: Studying Protein Oligomerization in the Nuclear Envelope of Living Cell
Speaker: Terry Jones
3:35 pm:
Speaker: Jeremy Mans, University of Minnesota
Subject: A Look at LHC Physics beyond the Higgs Discovery

The LHC collider and its detectors have been a generational effort to design, construct, and commission, with the primary mission to understand the nature of electroweak symmetry-breaking and the origin of rest-mass for fundamental particles. The discovery of the Higgs boson in 2012 marked a major achievement for particle physics, but this discovery has brought a number of long-standing puzzles into sharper focus. I will discuss several of these questions and how the University of Minnesota CMS group is addressing them. These questions include neutrino mass and left-right symmetry in particle interactions, the internal consistency of the Standard Model, and the nature of cosmological dark matter.

Friday, September 15th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
12:20 pm:
Speaker:  Michael Sammon, University of Minnesota
Subject:  Anomalous Thermodynamic Properties of Electron Accumulation Layer in SrTiO3

Due to the nonlinear dielectric response within SrTiO3 (STO),
an accumulation layer created by positive charges at the surface of the STO sample (x = 0) has an electron density pro file n(x) that slowly decays as 1=x^{12/7}. Previous works have shown that the slow decay of the tail leads to a divergence of kinetic coefficients when the scattering is primarily at the surface. Here we extend that work to the thermodynamic properties of the layer, and show that a similar divergence occurs in the magnetization and the specific heat when averaged over the accumulation layer. I will discuss several ways in
which the averaging may be truncated. The second half of the talk will focus on the capacitance as a function of the back gate voltage and explain how it can be used as an experimental tool for studying the tail of the distribution.

Speaker: There will be no seminar this week
2:30 pm:
MN Institute for Astrophysics Colloquium in Tate Lab of Physics and Astronomy 101
Speaker: Sarah Vigeland, U. Wisconsin, Milwaukee
Subject: Detecting Low-Frequency Gravitational Waves with NANOGrav
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.

For the past decade pulsar timing arrays (PTAs) have been monitoring
millisecond pulsars looking for the correlated timing residuals
caused by low-frequency gravitational waves (GWs) with frequencies
between 1 - 100 nHz. One type of source in this regime are
supermassive black hole binaries (SMBHBs). PTAs are sensitive to both
GWs from individual SMBHBs as well as a GW stochastic background produced
by the superposition of all SMBHBs. I will discuss the detection techniques
used by PTAs as well as the current status of the North American Nanohertz
Observatory for Gravitational Waves (NANOGrav) PTA.

Faculty Host: Vuk Mandic
3:35 pm:
Speaker: David Herzberg, Department of History - University at Buffalo
Subject: 'He Will be a Better Citizen as a Legitimate Addict': The Forgotten History of Harm Reduction in America’s First Opioid Epidemic
Refreshments served at 3:15 p.m.

This talk argues that medical maintenance of opiate addicts was an important element in the effective response to America’s first opioid epidemic in the late 19th and early 20th centuries. Physicians were relatively free to prescribe morphine to addicts despite federal authorities’ effort to stop them, because surveillance and policing were weak and state Medical Boards were often protective. Maintenance was clandestine and informal, however, and depended on addicts’ gaining sympathy and/or trust from individual physicians on a case-by-case basis. This restricted its reach along the familiar lines of American social prejudices, favoring addicts who could claim to be (as one described himself) “nice people in good standing.” This early and limited form of harm reduction did not ultimately serve as a model for future drug policy because of its secrecy and because of the racially-charged assumption that good addicts—rather than good policy—had helped bring an end to the opioid epidemic.

A Dorothy Bernstein Lecture in the History of Psychiatry

Speaker: Rafael Fernandes, University of Minnesota
Subject: To be announced.

Monday, September 18th 2017
12:15 pm:
12:30 pm:
National Postdoc Association Townhall in Mayo Memorial Auditorium, Room 3-100

We will be reviewing what we have done over the past year, including: explaining changes to the FLSA and its status under the new administration, advocating for postdoctoral rights with the White House, travelling to DC, changing our position in the University Senate, changing mentoring at the U, trying to create a career office, advocating with the National Postdoc Association, and more.

Food to be provided

Tuesday, September 19th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.
2:00 pm:
National Postdoc Association Seminar in Weaver-Densford Hall W2-110
Speaker: Noro Andriamanalina
Subject: My IDP

A seminar reviewing an efficient process at creating the professional agreement that guarantees a successful postdoctoral appointment and improving the relationship between you and your mentor.

4:30 pm:
There will be no seminar this week.

Wednesday, September 20th 2017
1:25 pm:
Speaker: Natalia Drichko, Johns Hopkins University
Subject: From spin liquid candidate to dipole liquid in quasi-two dimensional organic Mott insulators: a Raman scattering study.

One of the simplest models representing lattice frustration in magnetic materials is the triangular lattice Heisenberg antiferromagnet. It was shown theoretically that it orders into 120 degree order. However, a large number of spin liquid candidates on triangular lattice are found among quasi-two-dimensional molecular- based Mott insulators. One explanation is that new charge degrees of freedom that can emerge in molecular-based Mott insulators resulting in a quantum dipole liquid state. Studies of the materials has been hampered by a lack of spectroscopic information, since neutron scattering has generally not been possible.

We use Raman scattering to detect spectrum of magnetic excitations in these magnetic compounds. At first I will demonstrate a Raman scattering study of the helical antiferromagnet α -SrCr2O4 (T_N=42K). Further, we identify magnetic excitations in an antiferromagnetic compound k-(BEDT-TTF)2Cu[N(CN)2]Cl and a spin liquid candidate k-(BEDT-TTF)2Cu2(CN)3. We show that their spectrum of excitations is very different from that of another triangular lattice Mott insulator k-(BEDT-TTF)2Hg(SCN)2Br. Our data demonstrate the emergence of an on-site dipole degree of freedom in the latter material. Raman scattering allows us to detect dipole fluctuations both with vibrational molecular spectroscopy and through observation of a collective mode at about 8 meV. Heat capacity of k-(BEDT-TTF)2Hg(SCN)2Br demonstrates a linear term at low temperatures, supporting a scenario where composite spin and electric dipole degrees of freedom remain fluctuating down to the lowest temperatures.

Faculty Host: Natalia Perkins
3:00 pm:

An ice cream social for postdocs on campus! Show up, have some free ice cream, play games, talk to your fellow coworkers, and have a chance to relax on campus!

Speaker: D. Cronin-Hennessy, University of Minnesota
Subject: Paper reading: "Mechanical Detection and Measurement of the Angular Momentum of Light" by Richard A. Beth
4:30 pm:
CM Journal Club in PAN 120
Speaker: No CM Journal Club

Thursday, September 21st 2017
10:10 am:
Speaker: Prof. Bo Huang UCSF, Pharmaceutical Chemistry
Subject: Watching in the inner life of a cell: beyond super-resolution microscopy
Note room change, this week only.
Speaker: Evan Tyler and Pat Kelly
3:35 pm:
Speaker: Yan Song, University of Minnesota
Subject: Formation of Alfvenic Electromagnetic Plasma Structures and Auroral Particle Acceleration: -- Exploring Theory of High Energy Plasma Physics

The acceleration of charged particles to high energy and the associated emission of electromagnetic (EM) radiation produced by the accelerated electrons and ions, occur throughout space and cosmic plasmas. During these processes, a large part of stored free magnetic energy can rapidly and efficiently convert into the kinetic energy of charged particles producing non-thermal high energy particles and EM radiation. To find the mechanism of such high energy particle acceleration is one of the most important unsolved problems in space and cosmic plasmas.

In general, applying parallel electrostatic electric fields associated with charge separation is the simplest and powerful method to directly accelerate particles to high energy. However, once the electric fields are produced, they will quickly short themselves out by the motion of free charges. Thus, a central question in auroral physics is to find the mechanism by which long-lasting parallel electrostatic electric fields can be generated.

I will present the theory of the generation of parallel electrostatic electric fields (Song and Lysak, 2001, 2006), and point out that the generation of parallel electric fields is favored by a low plasma density and high magnetic shear. In the auroral current system, nonlinear Alfvenic interactions between Alfven wave packets can produce EM plasma structures, such as Alfvenic Double Layers. The Alfvenic Double Layer consists of localized long-lasting electrostatic electric fields, which are embedded in low density cavities and surrounded by enhanced magnetic stresses. These structures are dynamical in nature, where the Poynting flux carried by Alfven waves continuously supplies energy to the Alfvenic Double Layers to maintain strong electrostatic electric fields for a fairly long time. These structures become a new fundamental dynamical state in cosmic plasmas, which constitute powerful high energy particle accelerators.

It has been broadly considered that the magnetic reconnection is a fundamental physical process which is responsible for almost all high energy plasma processes in space and cosmic plasmas. Magnetic reconnection is described as a process occurring when oppositely directed magnetic field lines in a plasma are cut and rejoined. I will show that the crucial components of magnetic reconnection lack support from fundamental physical theory, and suggest that we should use the fundamental physical laws and principles to study “reconnection” related processes.

Friday, September 22nd 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.

The postdoc research symposium is a poster session where postdocs will have the chance to interact with judges and representatives from local industry. There will be awards both from the PDA and local companies and the awards ceremony will feature various speakers

You can register posters for the poster session here, there is no fee, there is a limit to the number of poster spots available.

If you have questions, please direct them to pda@umn.edu. We hope you'll take advantage of this opportunity to build a stronger postdoc community at the U.

Limited poster printing is available. Contact pda@umn.edu with questions.

12:20 pm:
Speaker: Daniel Shaffer, University of Minnesota
Subject: Properties of the Superconducting Gap in NbSe_2 Monolayers in Presence of in-Plane Magnetic Field.

NbSe_2 monolayers have been observed to superconduct in presence of relatively large (~35T) in-plane magnetic fields (as compared to the naïve Pauli limit estimate), an effect attributed to large out-of-plane spin orbit coupling (referred to in the literature as Ising SOC) in the niobium atom that pins electron spins perpendicular to the NbSe_2 plane. This lead some theorists to speculate about the effect of such magnetic fields on the nature of the superconducting gap function, which due to the SOC may be topologically non-trivial. In particular, it has been suggested that for fields above the Pauli limit, NbSe_2 becomes a nodal topological superconductor. In order to investigate this claim, I perform an RG analysis (without SOC) and solve the linearized gap equation using a simplified single band model that incorporates SOC. It turns out that while there exists a self-consistent solution to the gap equation in which an in-plane magnetic field induces a phase transition from a fully gapped phase to a nodal one, such a solution is neither favored by RG nor likely to occur in a real system due to in-plane (Rashba) SOC caused by ripples in the monolayer, which leads instead to a topologically trivial gap.

Speaker: Marilena Loverde (Stonybrook U.)
Subject: Neutrinos, Quintessence, and Structure Formation in the Universe

The large-scale structure of our universe (the distribution of galaxies on very large-scales for instance) contains a wealth of information about the origin, evolution, and matter content of the universe. Extracting this information relies crucially on understanding how galaxies and other biased objects trace the large-scale matter distribution. In a universe such as our own, with both cold dark matter and massive neutrinos, or in alternative cosmologies with clustered quintessence, this problem is much more complicated. I will discuss new tools that my group has developed to study gravitational evolution in cosmologies with multiple fluids, the novel signatures we have identified including a new probe of neutrino mass, and the broader implications for models of large-scale structure.

There will be no colloquium this week.
3:35 pm:
Speaker: Alison Gopnik, Department of Psychology, University of California - Berkeley
Subject: When Children are Better Learners than Adults: Theory Formation, Causal Models, and the Evolution of Learning
Refreshments served at 3:15 p.m.

In the past 15 years, we have discovered that even young children are adept at inferring causal relationships and that they do so in much the same way as scientists, using causal models and inductive inference to construct intuitive theories of the world. But are there differences in the ways that younger children, older children and adults learn? And do socioeconomic status and culture make a difference? I will present several studies showing a surprising pattern. Not only can preschoolers learn abstract higher-order principles from data, but younger learners are actually better at inferring unusual or unlikely principles than older learners and adults. This pattern also holds for children in Peru and in Headstart programs in Oakland, California. I relate this pattern to computational ideas about search and sampling, to evolutionary ideas about human life history, and to neuroscience findings about the negative effects of frontal control on wide exploration. My hypothesis is that our distinctively long, protected human childhood allows an early period of broad hypothesis search, exploration and creativity, before the demands of goal-directed action set in.

4:40 pm:
Speaker: Martin Greven, University of Minnesota
Subject: Doped Mott insulators and unconventional superconductors: exciting experimental research opportunities

Saturday, September 23rd 2017
08:30 am:
An International Conference Honoring Mitchell Luskin on the Occasion of his 65th Birthday

Summary: Multiscale modeling, theory, and computation have made fundamental contributions to many areas of physical, chemical, and biological sciences. Recent theoretical and experimental advances present new challenges for multiscale theory and computation. This conference will seek to stimulate new approaches and collaborations by bringing together both senior and junior researchers with expertise spanning molecular to continuum scales and stochastic to deterministic methods.

Some examples of talks of possible interest to Physics on the schedule:
Epitaxially Strained Elastic Films: Quantum Dots and Dislocations
The Problem of Small Temperatures in a Quantum Gas
Multiscale Dynamical Systems
Wandering in Flatland: the Wonders of 2D Materials
"Metastability: a Journey from Stochastic Processes to Semiclassical Analysis
Spin-Diffusions and Diffusive Molecular Dynamics

Register here

Sunday, September 24th 2017
08:30 am:
An International Conference Honoring Mitchell Luskin on the Occasion of his 65th Birthday

Summary: Multiscale modeling, theory, and computation have made fundamental contributions to many areas of physical, chemical, and biological sciences. Recent theoretical and experimental advances present new challenges for multiscale theory and computation. This conference will seek to stimulate new approaches and collaborations by bringing together both senior and junior researchers with expertise spanning molecular to continuum scales and stochastic to deterministic methods.

Some examples of talks of possible interest to Physics on the schedule:
Epitaxially Strained Elastic Films: Quantum Dots and Dislocations
The Problem of Small Temperatures in a Quantum Gas
Multiscale Dynamical Systems
Wandering in Flatland: the Wonders of 2D Materials
"Metastability: a Journey from Stochastic Processes to Semiclassical Analysis
Spin-Diffusions and Diffusive Molecular Dynamics

Register here

Monday, September 25th 2017
08:30 am:
An International Conference Honoring Mitchell Luskin on the Occasion of his 65th Birthday

Summary: Multiscale modeling, theory, and computation have made fundamental contributions to many areas of physical, chemical, and biological sciences. Recent theoretical and experimental advances present new challenges for multiscale theory and computation. This conference will seek to stimulate new approaches and collaborations by bringing together both senior and junior researchers with expertise spanning molecular to continuum scales and stochastic to deterministic methods.

Some examples of talks of possible interest to Physics on the schedule:
Epitaxially Strained Elastic Films: Quantum Dots and Dislocations
The Problem of Small Temperatures in a Quantum Gas
Multiscale Dynamical Systems
Wandering in Flatland: the Wonders of 2D Materials
"Metastability: a Journey from Stochastic Processes to Semiclassical Analysis
Spin-Diffusions and Diffusive Molecular Dynamics

Register here

12:15 pm:
There will be no seminar this week.

Tuesday, September 26th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.
4:30 pm:
See Joint Quantum Materials & Condensed Matter Seminar on Wednesday this week only.

Wednesday, September 27th 2017
1:25 pm:
Speaker:  Peter Abbamonte, University of Illinois, Urbana-Champaign
Subject: Bose condensation of excitons in a transition metal dichalcogenide

Bose condensation has shaped our understanding of macroscopic quantum phenomena, having been realized in superconductors, atomic gases, and liquid helium. Excitons are bosons that have been predicted to condense into either a superfluid or an insulating electronic crystal. But definitive evidence for a thermodynamically stable exciton condensate has never been achieved. In this talk I will describe our use of momentum-resolved electron energy-loss spectroscopy (M-EELS) to study the valence plasmon in the transition metal dichalcogenide semimetal, 1T‐TiSe2. Near the phase transition temperature, TC = 190 K, the plasmon energy falls to zero at nonzero momentum, indicating dynamical slowing down of plasma fluctuations and crystallization of the valence electrons into an exciton condensate. At low temperature, the plasmon evolves into an amplitude mode of this electronic crystal. Our study represents the first observation of a soft plasmon in any material, the first definitive evidence for exciton condensation in a three-dimensional solid, and the discovery of a new form of matter, “excitonium.”

Faculty Host: Martin Greven
To be announced.
7:00 pm:
2017 Misel Lecture in Memorial Hall, McNamara Alumni Center
Speaker: Wendy L. Freedman
Subject: THE UNIVERSE CONTINUES TO REVEAL SURPRISES

Over the past few decades, astronomers have for the first
time identified the major constituents of the universe.
Unexpectedly, the universe hardly resembles what we
thought only a couple of decades ago. The universe is filled
with dark matter more abundant than ordinary matter and
dark energy that is causing a runaway acceleration. Theory
is not yet able to explain this unexpected universe. New
giant telescopes planned for the next decade are likely to
reveal more surprises. In her lecture, Professor Freedman

Thursday, September 28th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Dr. Tejas M Gupte, University of Minnesota
Subject: To be announced.
Speaker: Matt Gomer
3:35 pm:
Speaker: Wendy Freedman, University of Chicago
Subject: A New Calibration of the Hubble Constant
Fall 2017 Misel Lecturer

The accuracy with which we can measure the Hubble
constant, Ho has been steadily increasing over the past
is based on measurement of distances and velocities to
galaxies in the local universe; for example, using Cepheid
variables and Type Ia supernovae. A model-dependent
Ho can be inferred from applying a cosmological model
to measurements of anisotropies in the cosmic microwave
background. Recently, these two precise techniques have
yielded values of Ho that disagree at more than 3-sigma.
This disagreement may be signaling errors in one or both
techniques. Alternatively, it could be signaling new physics
not currently included in the standard model of cosmology.
The Chicago-Carnegie Hubble Program is undertaking a
completely independent calibration of the Hubble constant
using red giant stars in the nearby universe. These stars
are proving to be both more precise and more accurate
than the traditional Cepheid variables. Moreover, with
the imminent launch of the James Webb Space Telescope
and new geometric parallaxes measured by Gaia, they will
provide a means of extending the distance scale beyond
the realm of Cepheids, and for measuring Ho to both a
precision and accuracy of 1%.

Friday, September 29th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
Subject: Organizational Meeting
12:20 pm:
Speaker: Mahendra DC, University of Minnesota
Subject: Giant spin-orbit torque from sputtered bismuth selenide films

The spin-orbit torque (SOT) arising from materials with large spin-orbit coupling promises a path for ultra-low power and fast magnetic-based storage and computational devices. We investigated the SOT from magnetron-sputtered BixSe(1-x) thin films in BixSe(1-x)/CoFeB heterostructures by using dc planar Hall and spin-torque ferromagnetic resonance (ST-FMR) methods. Remarkably, the spin Hall angle (SHA) was determined to be as large as 18.62 ± 0.13 and 8.67 ± 1.08, using the dc planar Hall and ST-FMR methods, respectively. Moreover, switching of perpendicular CoFeB multilayers using SOT from the BixSe(1-x)has been observed at room temperature (RT) with critical switching current density 4.3 × 105 A/cm2, which is the lowest-ever critical switching current density reported in a bilayer system. The transmission electron micrographs (TEM) show that the sputtered BixSe(1-x) films have a polycrystalline structure, whose grain size decreases with the film thickness. Quantum transport simulations using realistic sp3 tight binding model suggests that the giant SOT in sputtered BixSe(1-x)is due to a quantum confinement effect, whose spin-accumulation enhances with reduced size and dimensionality. The demonstrated giant SHA, ease of growth of the films on a silicon substrate, and successful growth and switching of perpendicular CoFeB multilayers on BixSe(1-x) film provide an avenue for the use of the topological insulator (TI) BixSe(1-x) as a spin-current generator in SOT-based memory and logic devices.

Speaker: Kiel Howe (Fermilab)
Subject: Flavorful UV Instantons and the Strong CP Problem

We describe a new solution to the strong CP problem inspired by the massless up quark solution. At high energies, QCD is embedded in a SU(3)xSU(3)xSU(3) model, with each matter generation charged under a different site. Instanton effects are unsuppressed at the scale of Higgsing to the SM diagonal QCD, and a set of anomalous U(1)_PQ symmetries removes the low-energy strong CP phase. A non-zero theta parameter is generated at loop level near current bounds. Similar models can also lead to a heavy axion solution to the strong CP problem.

Speaker: No colloquium this week
Subject: See the Misel lecture information for September 27th
3:35 pm:
Speaker: Amy Bix, Department of History - Iowa State University
Subject: Inviting Girls Into the Lab: the Rise of Diversity Advocacy in STEM, 1950-Present
Refreshments served at 3:15 p.m.

One of the biggest transformations in modern science and engineering isn't a particular discovery, invention, or technique, but a revolution in assumptions about who can and should enter those disciplines. For years, American efforts focused on steering more young white men into science and engineering. By the mid-1950s, some scientists and engineers began programs to open opportunities to broader groups of youngsters. Their advocacy fostered wide-ranging campaigns to expand STEM opportunities for K-12 female students, which came to command major support from scientific and technical organizations, corporations, government, community groups, educators, even celebrities. This talk explores when, how, and why evolving ideas about gender roles, education, and the nature of STEM generated the modern movement for STEM diversity and outreach.

4:40 pm:
Speaker: Yong-Zhong Qian, University of Minnesota
Subject: The Origin of the Elements and A Supernova Trigger for the Formation of the Solar System

A brief introduction to nucleosynthesis and chemical evolution will be given. Production of stable and radioactive nuclei by supernovae will be discussed in connection with the trigger for the formation of the solar system.

Saturday, September 30th 2017
12:00 pm:
School Picnic in Boom Island Park Shelter B

All members of the School and their families are invited to join a picnic at Boom Island Park Shelter B. I will also be sending out another reminder email to the department this week, but figured it couldn't hurt to try and get as much ad space as we can!

Monday, October 2nd 2017
12:15 pm:
Speaker: Samir Banik, NISER, Bhubaneswar, India
Subject: LIPs analysis in SuperCDMS

Standard model for particle physics does not demand quantization of particle charges. This opens the possibility of finding particles with fractional charges. These particles lose energy at a rate which is proportional to square of charges, much more slowly than any known minimum ionizing particles. These particles are commonly termed as Lightly Ionizing Particles or LIPs. SuperCDMS low threshold detectors offer an opportunity to search for LIPs with very small fractional charges. I will discuss about some previous LIPs search experiments and will present LIPs analysis in SuperCDMS.

Faculty Host: Priscilla Cushman

Tuesday, October 3rd 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Mark Engebretson, Augsburg College
Subject: Recent observational studies of EMIC waves
4:30 pm:
Speaker: Eric McCalla, Chemical Engineering and Material Sciences
Subject: A gap in the literature: heat capacity in Nb-doped SrTiO3

Wednesday, October 4th 2017
1:25 pm:
Speaker: Tobias Gulden, Technion - Israel Institute of Technology, Haifa
Subject: Prethermal states in slowly driven many-body systems

Topological phases offer diverse novel properties of matter. These are mostly determined by material properties which can not easily be changed. An alternative are driven topological systems such as Floquet topological insulators and charge pumps. In these cases application of an external time-periodic field allows for easy control of the topology of the system. In this talk I discuss general properties of slowly driven systems in the presence of interactions with the example of a charge pump. Intraband scattering thermalizes all particles within one band which makes topological properties of partly filled bands accessible. On the other hand interactions also cause excitations to the other band with opposite topological index. I will show that for a wide class of systems there exists a prethermal state in which one band is fully thermalized while the other band remains unoccupied. During this time window the topological properties are experimentally accessible.

Faculty Host: Alex Kamenev
Subject: "The modified Newtonian dynamics—MOND and its implications for new physics"
4:30 pm:
CM Journal Club in PAN 120
There is no journal club this week.

Thursday, October 5th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Ahmed Haikal, University of Minnesota, Duluth
Subject: Macromolecular Crowding Effects on Excited-State Dynamics of Hetero-FRET Probes in Mimetic Environments

Macromolecular crowding is prevalent in all living cells due to the presence of proteins, nucleic acids, and organelles. Cellular crowding is heterogeneous and is known to influence biomolecular transport, biochemical reactions, and protein assembly and folding. Emerging evidence suggests that some cell pathologies may be correlated with compartmentalized crowding. As a result, there is a need for robust biosensors to quantify crowding both spatially and temporally in living cells. Importantly, those biosensors should be compatible with noninvasive and quantitative micro-spectroscopy methods. I will highlight our recent wavelength-dependent excited-state dynamics of new hetero-FRET (mCerulean–linker–mCitrine) biosensors in environments of varying homogeneous and heterogeneous viscosities. Using time-resolved fluorescence and polarization anisotropy measurements, we elucidate the effects of the linker length and flexibility on the energy transfer efficiency as a function of the surrounding environment. Our results represent an important step towards the application of quantitative and non-invasive approaches to investigate macromolecular crowding and protein-protein interactions in living cells using hetero-FRET probes.

Speaker: Chris Nolting
3:35 pm:
Speaker: David Kaiser, MIT
Subject: Testing Bell’s Inequality with Astrophysical Observations

Albert Einstein once dubbed quantum entanglement "spooky action at a distance," and the concept remains one of the starkest examples of how quantum theory differs from our usual intutions about space, time, and matter. Physicists have tested Bell’s inequality experimentally for over four decades, and have always found results consistent with quantum theory; today entanglement is at the heart of next-generation devices like quantum computers and quantum encryption. Yet every experimental test to date has been subject to one or more "loopholes," which could possibly account for the results even in the absence of genuine quantum entanglement. This talk describes the latest experimental tests of quantum entanglement, including a new series of experiments that uses some of the oldest light in the universe to address the last major loophole and pave the way for a genuinely loophole-free test of Bell’s inequality.

Faculty Host: Michel Janssen

Friday, October 6th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Christopher Plumberg, University of Minnesota
Subject: To be announced
12:20 pm:
Speaker: Justin Watts, University of Minnesota
Subject: Elliott-Yafet Scaling of Spin Lifetimes in Al and Cu Non-Local Spin Valves

Spin relaxation in metals is often discussed within the framework of Elliott-Yafet (EY) relaxation, where the spin relaxation and elastic scattering rates are related via a proportionality constant referred to as the EY parameter. Although this parameter is known for some scattering sources (e.g., phonons) in certain elemental metals, experimental knowledge and general understanding remains limited. Here, we significantly expand the experimental knowledge base by determining EY phonon and defect parameters in Al and Cu non-local spin valves with channel thicknesses from 400 to 20 nm. For Al we find a surprisingly broad range for the phonon parameter which contrasts with expectations of a constant value for a specified material. In particular, we find an unexpected size dependence that is discussed in terms of finite size effects and the Debye temperature.These results identify factors limiting metallic spin diffusion lengths and hence the performance of nanoscopic spin transport devices.

Speaker: Edwin Ireson (U. Minnesota)
Subject: Worldsheet-Induced Corrections to the Holographic Veneziano Amplitude

The Veneziano amplitude is a very useful tool to model meson scattering in confining gauge theories, with many attractive features, namely providing an example of amplitudes with a clear linear Regge trajectory. But this formulation is incomplete- it effectively only exist in theories where the coupling never runs. We expect the Regge trajectory to bend away from linearity due to the running of the coupling at higher energies: we propose a way of doing so, using string theory and the holographic duality, in order to improve on a long-standing result of Makeenko and Olesen.

Speaker: Anna Nierenberg, Ohio State U
Subject: Dwarf galaxy formation and the nature of dark matter
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.

The abundance of low mass dark matter halos (M_vir <10^9 M_sun) provides key insight into the nature of dark matter, as this abundance depends on the free-streaming length of dark matter at early times and thus its particle properties. Measuring the abundance of low mass halos is difficult as stars become increasingly poor tracers of structure on these scales owing to the complex and not yet well understood physics of star formation in these systems. I will present two complementary approaches to resolving these issues. First I will present measurements of the properties of faint satellite galaxies at a range of redshifts and around a variety of host types and demonstrate how these place strong new constraints on theoretical models of star formation in low mass halos. Secondly, I will present a novel approach to gravitational lensing which makes it possible directly measure the subhalo mass function to masses well below the mass scale of the missing satellite problem in a much larger sample of systems than previously possible. I will conclude by discussing future prospects for these programs given the next generation of ground and space based facilities.

Faculty Host: Liliya L.R. Williams
3:35 pm:
Speaker: David Kaiser, Program in Science, Technology and Society - Massachusetts Institute of Technology
Subject: Cold War Curvature: Measuring and Modeling Gravity in Postwar American Physics
Refreshments served at 3:15 p.m.

A popular image persists of Albert Einstein as a loner, someone who avoided the hustle and bustle of everyday life in favor of quiet contemplation. Yet Einstein was deeply engaged with politics throughout his life; indeed, he was so active politically that the FBI kept him under surveillance for decades. His most enduring scientific legacy, the general theory of relativity -- physicists' reigning explanation of gravity and the basis for nearly all our thinking about the cosmos -- has likewise been cast as an austere temple standing aloof from the all-too-human dramas of political history. But was it so? By focusing on two examples of research on general relativity from the 1950s and 1960s -- the Shapiro time-delay test and early efforts in numerical relativity -- this lecture will examine some of the ways in which research on Einstein's theory was embedded in, and at times engulfed by, the tumult of world politics.

Co-sponsored with the School of Physics and Astronomy

4:40 pm:
Speaker: Pat Kelly, University of Minnesota
Subject: "Using Transients and Gravitational Lensing to Probe Stellar Astrophysics, Dark Matter, and Cosmology"

Monday, October 9th 2017
12:15 pm:
Speaker: Anthony Villano, UMN
Subject: The Sensitivity Frontier for Cryogenic Semiconductor Detectors

Cryogenic semiconductor particle detectors are undergoing revolutionary advancements that can greatly improve the reach of dark matter direct detection experiments. In order to fully realize the potential of these detector advancements, major challenges in ultra-low-energy calibration and device physics must be overcome. I will discuss techniques to use sub-keV energy deposits to bring the physics of detector response into sharper focus. Using the framework developed to study detector response at this level we will then muse about future devices with even more extraordinary capabilities.

Faculty Host: Priscilla Cushman

Tuesday, October 10th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Bob Lysak and Yan Song, University of Minnesota
Subject: Report on the 13th International Conference on Substorms

Wednesday, October 11th 2017
1:25 pm:
Speaker: Chien-Hung Lin, University of Minnesota
Subject: Protected surface states of 3D bosonic symmetry-protected topological phases

We show that the surface states of three-dimensional bosonic symmetry protected topological (SPT) phases with unitary symmetries are protected: their surface must be gapless as long as the symmetry is not broken and the surface is not topologically ordered. We demonstrate the result by constructing an exactly soluble lattice model which realizes a nontrivial Z2×Z2 SPT phase in three dimensions and showing that the model has protected surface states.

Faculty Host: Fiona Burnell
Speaker: Anthony Villano, UMN
Subject: The Sensitivity Frontier for Cryogenic Semiconductor Detectors

Cryogenic semiconductor particle detectors are undergoing revolutionary advancements that can greatly improve the reach of dark matter direct detection experiments. In order to fully realize the potential of these detector advancements, major challenges in ultra-low-energy calibration and device physics must be overcome. I will discuss techniques to use sub-keV energy deposits to bring the physics of detector response into sharper focus. Using the framework developed to study detector response at this level we will then muse about future devices with even more extraordinary capabilities.

4:30 pm:
CM Journal Club in PAN 120
To be announced.

Thursday, October 12th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Wendy Gordon, Dept. of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota
Subject: Decoding mechanotransduction mechanisms of cell-surface receptors

Alteration of mechanical forces is an emerging factor in diseases like cancer. Changes in macroscopic stiffness in disease are accompanied by a wealth of changes in a cell’s tensional homeostasis at a molecular level where mechanotransduction signaling pathways are aberrantly activated. Our lab aims to understand molecular mechanisms utilized by cell-surface receptors to sense and respond to physical stimuli in the cellular environment. I will discuss a new bioluminescence resonance energy transfer (BRET)-based molecular tension sensor that we have developed to help identify mechanosensing proteins in the cell. I will also discuss the molecular mechanisms utilized by the extracellular matrix receptor dystroglycan to regulate proteolysis.

Speaker: Qi Wen and John Phillips
3:35 pm:
Speaker: Clem Pryke, University of Minnesota
Subject: Studying the Beginning of the Universe from the Bottom of the World

The theory of Cosmic Inflation postulates that our entire observable universe
was spawned from a quantum fluctuation in an incredibly brief burst of hyper
expansion. Some believe that the evidence for Inflation is already
overwhelming (especially now that the results from the Planck space mission
are in). However, there are determined skeptics, and such extraordinary claims
require extraordinary evidence. Fortunately there is a chance that we can
obtain this! During the exponential inflationary expansion perturbations of
all kinds will have been injected into the fabric of spacetime, including a
background of gravitational waves. It turns out that our best hope to detect
these is to look for their imprint in the polarization pattern of the cosmic
microwave background (CMB). The BICEP/Keck telescopes, located at the South
Pole in Antarctica are currently the world leaders in this endeavor. In this
talk, I will describe the instruments, the results, and the continuing hunt
for inflationary gravitational waves.

Speaker: Lawrence Rudnick, University of Minnesota
Subject: A Walk on the Dark Side

Our Universe is comprised of far more than meets the eye. For 13.8 billion years, gravity has been creating enormous bound structures, the largest of which are clusters of galaxies. Modern telescopes are uncovering an astonishing variety of structures in these clusters which are invisible to the human eye – from X-ray emitting gas at 100s of millions of degrees, to supermassive black holes at the centers of cluster galaxies, to the popularized but not yet understood dark matter that holds everything together. Even the enigmatic dark energy plays a role in cluster formation. Our tour of clusters will start with the first recognition of curious concentrations of fuzzy objects in the sky to the latest discoveries using telescopes across the Earth and space.

About the Speaker: Professor Rudnick is a Distinguished Teaching Professor of Astrophysics, whose research focuses on clusters of galaxies and other large scale structures in the Universe. He uses ground and space telescopes, primarily in the radio and X-ray part of the spectrum. His teaching includes eclectic freshman seminars such as “The Ultimate Questions,” and “Nothing.” Professor Rudnick has been active for many years with a variety of television, radio, and other public programming, and is now working toward the opening of the Bell Museum and Planetarium in 2018 on the St. Paul campus.

Friday, October 13th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
This week's seminar has been postponed to Monday, Oct. 16th, at 1:25
12:20 pm:
Speaker: David Harrison, University of Minnesota
Subject: Measurements of 1/f Noise in CuMn and AgMn Thin Films

We have measured the 1/f noise in the spin glass state of CuMn and AgMn thin films. Our results are consistent with previous measurements that have demonstrated low-frequency resistance fluctuations abruptly increase in magnitude as a spin glass is cooled. It is believed that the noise originates from fluctuations in the orientation of the local magnetic moments (spins'') within the spin glass. It was originally suggested that the abrupt increase in the noise magnitude corresponded to the glass temperature of the spin glass system. However, we have found that the noise increases at a somewhat lower temperature, indicative of a second transition. Some theoretical work has predicted transitions below the glass temperature, though none has been previously observed. We are working to understand the nature of this transition presently.

Subject: Swampland Conjectures and their Applications to Cosmology and Particle Physics
Speaker: Eliza Kempton, Grinnell College
Subject: Revealing the Atmospheres of Extrasolar Super-Earths
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.

Discoveries of extrasolar planets over the last two decades have reshaped our understanding of how planetary systems form. Super-Earths – planets intermediate in size/mass between Earth and Neptune – do not exist in our Solar System, and the discovery of such planets poses a challenge to theories of planetary formation and composition based on the Solar System paradigm. Through observations of the atmospheres of these planets, we can learn about their formation history, their climate, and in some cases their propensity to support life. This talk will focus on the modeling of super-Earth atmospheres as it relates to current and future observations. I will detail the current state of characterization efforts for super-Earth atmospheres, focusing on the challenges and successes in modeling and interpreting the early observations of these objects. I will conclude with a forward-looking view of super-Earth atmospheric studies over the next 5-10 years, in the era of the James Webb Space Telescope (JWST) and 30-meter class ground-based telescopes.

Faculty Host: Liliya L.R. Williams
3:35 pm:
Speaker: Rebecca Kukla, Department of Philosophy - Georgetown University
Subject: Structural Bias and the Commercialization of Medicine
Refreshments served at 3:15 p.m.

The rapid and massive commercialization and privatization of medical research and practice constitutes a seismic shift in how medical knowledge is built, disseminated, and applied. In this presentation, I examine the epistemological (as opposed to the narrowly ethical) effects of this commercialization. I consider how private interests shape what gets researched, using what methods, and how research results are communicated, as well as how these interests shape clinical practice and even our theoretical understanding of what counts as a disease. I argue that commercialization and private interests result in various epistemically distorting biases being built directly into how we organize medical research and practice, quite independently from anyone’s intentions or conscious goals.

4:40 pm:
Speaker: Dan Dahlberg, University of Minnesota
Subject: Nano/meso scale magnets and fundamental statistical mechanics

Monday, October 16th 2017
09:00 am:
Live-stream of press conference, followed by Q & A with LIGO members.

LIGO, Virgo, and about 70 observatories will announce new details and discoveries made in the ongoing search for gravitational waves. This will take place at the National Press Club in Washington, D.C, which will be live-streamed.

12:15 pm:
Speaker: Tom Jones, UMN
Subject: Particle Acceleration in Galaxy Clusters
1:25 pm:
Speaker:  Jens Andersen, Norwegian University of Science and Technology
Subject: QCD thermodynamics. Hard-thermal-loop perturbation theory vs lattice
Note change of time and day for the seminar, this week only

The perturbative series for finite-temperature field theories has very poor convergence properties and one needs a way to reorganize it. In this talk, I review one way of reorganizing the perturbative series thermal QCD, namely hard-thermal-loop perturbation theory (HTLpt). I will present results for the pressure, trace anomaly, speed of sound and the quark susceptibilities from a 3-loop HTLpt calculation. A careful comparison with available lattice data shows good agreement for a number of physical quantities.

Speaker: Prof Oded Agam, Hebrew University Jerusalem,
Subject: Saturation of strong electron-electron umklapp scattering at high temperature.
Please note change of time, room and day for the seminar, this week only.

It is usually believed that in clean metals, at finite temperature, the electron-electron umklapp scattering is proportional to the inelastic scattering rate, 1/\tau_{ee}. In this talk it will be shown that, for three dimensional systems, when \hbar/\tau_{ee} is of order or larger than the band splitting energy, the umklapp scattering rate saturates to a value which is independent of both \tau_{ee} and the temperature, T. This phenomenon sheds new light on the old problem of the resistivity saturation at high temperature.

Faculty Host: Alex Kamenev

Tuesday, October 17th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
To be announced.
3:30 pm:
CM Journal Club in Tate-301-20
Speaker: Laxman Raju Thoutam, CEMS, University of Minnesota
Subject: Research update: Conductivity and beyond at the LAO/STO interface
Please note change of time, room and day for the seminar, this week only.
4:30 pm:
See Joint Quantum Materials & Condensed Matter Seminar on Thursday this week only.

Wednesday, October 18th 2017
1:25 pm:
Speaker: Joe Orenstein, UC Berkeley
Subject: Is there a bound on the nonlinear optical response of crystals?

The second-order nonlinear response, defined by the relation, J^((2)) (ω±ω)=σ^((2) ) (ω)E_ω^2, is allowed only in media without a center of inversion. A new class of inversion breaking materials, “Weyl semimetals,” have been synthesized and are currently under intense investigation. Recently we reported that the first of this class of materials to be discovered, the transition metal monopnictides such as TaAs, and NbAs, exhibit the largest σ^((2) ) (ω)E_ω^2 of any known crystal. Large values of σ^((2) ) (ω) are of interest for applications involving frequency generation and conversion of light to electrical current. The observation of a “giant” response raises two related questions for which I will attempt to provide partial answers: what is special about TaAs, and is there an upper bound on σ^((2) ) (ω) of inversion-breaking crystal?

Faculty Host: Martin Greven
To be announced.

Thursday, October 19th 2017
09:00 am:
Thesis Defense in Tate 201-20
Speaker: Allison Kennedy, University of Minnesota
Subject: SuperCDMS Prototype Detector Design and Testing
This is the public portion of Ms. Kennedy's thesis defense. Her advisor is Vuk Mandic.

The SuperCDMS test facility at University of Minnesota aids in the detector R&D and characterization of prototype detectors, as part of the scale-up effort for SuperCDMS SNOLAB. This thesis presents the first full ionization and phonon characterization study of a 100 mm diameter, 33 mm thick prototype Ge detector with interleaved phonon and ionization channels. Results indicate that 100 mm diameter, interleaved Ge detectors show potential for use in SuperCDMS SNOLAB.

As part of detector R&D, the Minnesota test facility also looks beyond the next stage of SuperCDMS, investigating larger individual detectors as a means to easily scale up the sensitive mass of future searches. This thesis presents the design and initial testing results of a prototype 150 mm diameter, 33 mm thick silicon ionization detector. The detector was operated with contact-free ionization electrodes to minimize bias leakage currents, which can limit operation at high bias voltages. The results show promise for the operation of both large volume silicon detectors and contact-free ionization electrodes for scaling up detector mass and bias.

10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Jose Alejo Amaya, Engelhart/Adamala lab, GCD, University of Minnesota
Subject: The Unexplored Mechanisms and Regularatory Functions of Ribsome Translocation

In every cell, protein synthesis is carried out by the the ribosome, a complex macromolecular RNA-protein assembly. Single-molecule fluorescence methods have been applied to decipher the mechanism and regulatory roles of the multi-step process of translocation that accompanies every round of translation. The elongation factor G(EF-G)-catalyzed movement of substrates through the ribosome was examined from several perspectives or signals reporting on various ribosomal degrees of freedom. Two states interconvert in the presence of EF-G(GDP), displaying novel head domain motions, until translocation is completed. In order to test if the mentioned state fluctuations leading to translocation are correlated to the engagement of the P-site by the incoming peptidyl-tRNA, the translocation of miscoded tRNAs was studied. Severe defects in the late stages of translocation reveal the correlation between this new stage of translocation and P-site tRNA engagement.

11:00 am:
Special Seminar in B50 Tate
Speaker: Andrew Matas, University of Minnesota
Subject: Implications of LIGO announcements
Speaker: Trevor Knuth
3:35 pm:
Speaker: Paula Heron, University of Washington
Subject: Preparing Physics Students for 21st Century Careers: The PHYS21 Report

With support from the NSF IUSE program, the AAPT and APS formed a Joint Task Force on Undergraduate Physics Programs (JTUPP). The task force reviewed employment data, surveys of employers, and reports generated by other disciplines. We also met with physicists in selected industries to get their views on the strengths and weaknesses of physics graduates, commissioned a series of interviews with recent physics graduates employed in the private sector, and identified exemplary programs that ensure that all of their students are well prepared to pursue a wide range of career paths. The resulting report “PHYS21: Preparing Physics Students for 21st Century Careers” describes the skills and knowledge that undergraduate physics degree holders should possess to be well prepared for a diverse set of careers and makes recommendations intended to help departments and professional associations support student career preparation.

Paula R.L. Heron is a Professor of Physics at the University of Washington. She holds a B.Sc. and an M.Sc. in physics from the University of Ottawa and a Ph.D. in theoretical physics from Western University. She joined the Physics Department at the University of Washington in 1995. Dr. Heron’s research focuses primarily on student ability to apply what they have learned about the dynamics of point particles in more advanced contexts involving elastic media, rigid bodies, etc. She has given numerous invited talks on her research at national and international meetings and in university science departments. Dr. Heron is co-Founder and co-Chair of the biannual “Foundations and Frontiers in Physics Education Research” conference series, the premier venue for physics education researchers in North America. She has served on the Executive Committee of the Forum on Education of the American Physical Society (APS), the Executive Committee of the Topical Group on Physics Education Research of the APS, the Committee on Research in Physics Education of the American Association of Physics Teachers (AAPT) and on the ad hoc National Research Council committee on the status and outlook for undergraduate physics education. She co-chaired the Joint Task Force on Undergraduate Physics Programs of the APS and AAPT, which produced the report Phys21: Preparing Physics Students for 21st Century Careers. She also serves as Associate Editor of Physical Review – PER. She was elected Fellow of the APS In 2007 and in 2008 she shared the APS Education award with colleagues Peter Shaffer and Lillian McDermott. Dr. Heron is a co-author on the upcoming 2nd Edition of Tutorials in Introductory Physics, a set of instructional materials that has been used in over 200 institutions in the US and that has been translated into German and Spanish.

Faculty Host: Kenneth Heller

Friday, October 20th 2017
08:00 am:
Untitled in Physics
12:20 pm:
Speaker: Timothy Peterson, University of Minnesota
Subject: Ferromagnetic resonance measurements of dynamic magnetization damping in Co(2)FeAl thin films in the ultra-low damping regime

Ferromagnetic resonance (FMR) linewidth measurements are used to study the magnetization damping constant of Heusler compound Co(2)FeAl. The FMR linewidth is found to be highly anisotropic and exhibit a nonlinear dependence on FMR frequency, contrary to simple expectations . A magnon-magnon scattering theory is used to explain the linewidth behavior, which reveals a ultra-low intrinsic damping constant of less than 10^-3. Prospects for further exploration of intrinsic damping processes based on these results are discussed.

Speaker: Stefania Gori (U. Cincinnati)
Subject: Novel windows into the dark sector

Dark Matter (DM) provides strong evidence for physics beyond the Standard Model (SM). Arguably, rather than suggesting a specific mass scale for New Physics, it may point to a dark sector, weakly-coupled to the SM, as hinted at by the comparable abundances of dark matter and visible baryons. In the past few years, a program of new experiments has expanded DM searches far beyond the WIMP paradigm to include new hidden forces and matter. While this program has made impressive progress, there are considerable challenges that must be overcome to fully explore the viable dark sector scenarios over a wide range of mass scales. In this talk, I will discuss on the one hand the unprecedented opportunity to test electroweak scale dark sectors using high-energy experiments, and in particular the high-luminosity LHC. On the other hand, I will present new search strategies to test lighter dark sectors at low-energy high-intensity experiments, with a special emphasis on existing and planned experiments at Fermilab.

Speaker: Nicholas Battaglia, Princeton University
Subject: Large-Scale Structure Information Encoded in the Cosmic Microwave Background
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.

A new window into the growth and evolution of large-scale structure has opened up with the recent measurements kinetic Sunyaev-Zel’dovich (SZ) effect. I will show how we can constrain the important baryonic process that govern galaxy formation through SZ measurements. Additionally, I will describe the prospects for future cosmic microwave background experiments to constrain fundamental physics from kinetic SZ observations and how to mitigate the modeling uncertainties associated with the baryonic processes that will limit these constraints.

Faculty Host: Shaul Hanany
3:35 pm:
Speaker: Victor Boantza, History of Science and Technology - University of Minnesota
Subject: "Fluidity, Elasticity, and Activity: Conceptualizing Air from Boyle to the Early Newtonians"
Refreshments served at 3:15 p.m.

The category of ‘permanently elastic fluids’, which by the late eighteenth century was widely used by investigators of pneumatic phenomena, embodies key aspects of the history of air as it gradually turned into a chemical species and a physical state of matter. In this talk, I explore the evolution of early conceptions of Air in terms of fluidity, elasticity, and
material activity. I examine the interplay between theory and practice from early mechanistic depictions of Air, through Boyle’s use of the notion of ‘springiness’, to the emergence of various conceptions of fluids, including aerial ones, based on the work of Boyle, Newton, and their contemporaries. Mobilizing new accounts of elastic fluids, in the early 1700s pneumatic practitioners drew analogies between Air and Fire. In the 1720s–30s, following Stephen Hales’s experimental demonstration that air could be fixed in and obtained from solid and liquid substances, natural philosophers and chemists introduced further distinctions between atmospheric Air and views of air as an active material agent and a form of matter. By the middle of the century, increasingly prevalent references to permanently elastic fluids marked the culmination of these developments. This reading challenges and complements the accepted narrative of the rise of pneumatic chemistry as essentially driven by a series of landmark experiments, facilitated by technological innovations ranging from the air pump to the pneumatic trough.

Promotion & Tenure Seminar - Co-sponsored by the School of Physics and Astronomy

4:40 pm:
Speaker: Marvin Marshak, University of Minnesota
Subject:  The big questions in particle physics

Monday, October 23rd 2017
12:15 pm:
Speaker: Colin Hill, Department of Physics, Columbia University
Subject: New Information in Ancient Photons: Novel Approaches to CMB Foregrounds and Secondary Anisotropies

Studies of the cosmic microwave background (CMB) radiation have driven the current era of precision cosmology. The tightest cosmological constraints to date have been derived from the primary CMB anisotropies, which predominantly probe the universe in its infancy. However, CMB experiments have recently entered a new regime in which constraints derived from the secondary anisotropies -- sourced by effects between our vantage point and the surface of last scattering -- substantially improve upon those derived from the primary anisotropies alone. Moreover, the secondary anisotropies contain valuable astrophysical information about the distribution and thermodynamic properties of baryons and dark matter at late times. I will describe new approaches to extract information from these signals, highlighting recent results related to the thermal (tSZ) and kinematic Sunyaev-Zel'dovich (kSZ) effects, which refer to the Compton-scattering of CMB photons off ionized gas with high temperature or non-zero bulk momentum, respectively. In particular, I will show how the kSZ effect probes the abundance of ionized gas in and around modern-day galaxies, which I have used to resolve the long-standing "missing baryon problem". I will then discuss new methods for combining multi-frequency CMB data to extract these signals in the presence of large (and correlated) foregrounds, with additional applications to CMB polarization analyses. I will conclude with a look ahead to such measurements with the Simons Observatory (SO), focusing on methods to determine the optimal frequency coverage of the large-aperture SO telescope for secondary anisotropy science, including CMB lensing.

Faculty Host: Shaul Hanany

Tuesday, October 24th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week. Please attend Stuart Bale's MIFA Colloquium.

Wednesday, October 25th 2017
1:25 pm:
Speaker: Cindy Regal, University of Colorado-Boulder
Subject: Prospects for an optical link to superconducting qubits via engineered micromechanical motion
Faculty Host: Clement Pryke
Speaker: Doug Glenzinski, Fermilab
Subject: The Mu2e Experiment
4:30 pm:
CM Journal Club in Tate 201-20
Speaker: Ruiqi Xing
Subject: Machine Learning circumvents sign problem in Quantum Monte Carlo

The journal club talk will be about the paper [1]. I will first introduce the famous fermion sign problem [2] in Determinantal Quantum Monte Carlo(DQMC) [3], and then discuss how to circumvent it using a method developed in machine learning community, convolutional neural networks. Introduction to neural networks [4] will be given. In the end, A successful application of this method to distinguish phases and to identify quantum phase transitions will be presented.

Thursday, October 26th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Hao Wu, University of Minnesota
Subject: To be announced.
10:30 am:
Thesis Defense in 110 PAN
Speaker: Qianhui Shi, University of Minnesota
Subject: Magneto-transport in quantum Hall systems at high Landau levels
This is the public portion of Ms. Shi's thesis defense. Her advisor is Michael Zudov.
Speaker: Micaela Bagley
3:35 pm:
Speaker: Cindy Regal, University of Colorado-Boulder
Subject: Interferometry in a Strong Light

Optical interferometry is at the heart of many precise measurements from gravitational wave searches to microscopy. Generally one improves interferometer precision by increasing the light intensity, as well as by calming the many technical sources of noise that can perturb the mirrors or optical path. However, at extreme levels of light strength where radiation forces are significant, a new and interesting disturbance should appear – the quantum shaking associated with random arrival of individual photons at a mirror of the interferometer. This quantum backaction of light has been long foreseen and played a formative role in quantum optics theory. In this talk I will discuss an experiment in which we used a particularly compliant micro-scale drum to observe backaction in an interferometer, and demonstrate how quantum correlations can improve measurement in the presence of backaction. In this strong-light limit, interferometer mirrors can also be used as a nonlinear medium to manipulate light – for example to make squeezed light.

Faculty Host: Clement Pryke

Friday, October 27th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
12:20 pm:
Speaker: Yilikal Ayino, University of Minnesota
Subject: Superconductivity in NdxSr1-xTiO3 Thin Films

Superconductivity in SrTiO3(STO) has remained an open question for more than half a century. In this talk I will present experimental results showing superconductivity in Nd doped STO thin flims (50-250 nm), where Nd is expected to carry a net magnetic moment. All the samples we studied show an anisotropic resistance along the two in-pane orthogonal directions, where the normal state resistances along the two directions differ by more than several factors. Although the normal state resistances between the channels seem to be qualitatively similar, the resistive superconducting transition is drastically different. Along the channel with larger normal state resistance we observe a smooth transition from metallic to superconducting state with decreasing temperature (“normal channel”), but along the channel with smaller normal state resistance we observe an insulating state (resistance rising by up to an order of magnitude in a narrow temperature range) between the metallic and superconducting states. The onset of the insulating state is closely related to superconductivity and that its behavior is qualitatively different from known effects of granularity or superconducting fluctuations in an insulating matrix. For the “normal channel” the out of plane upper critical field as a function of temperature shows opposite curvature from what would be expected based on WHH theory and that the critical field doesn’t seem to saturate with decreasing temperature. I will present possible explanations for such anomalous behavior, including effects related to magnetic impurities and two-band superconductivity.

Speaker: Gustavo Marques Tavares (Stanford)
Subject: Detecting Dark Matter from Supernovae

The central region of Supernovae are one of the hottest and densest regions in the Universe. Due to the high temperatures, particles with masses below hundreds of MeV can be copiously produced if they have non-negligible couplings to the Standard Model. In this talk I will show that in a wide range of dark sector models, the dark matter flux from past Supernovae could be sufficiently large enough to be detected in dark matter direct detection experiments.

Speaker: Stuart Bale, Berkeley Space Science Lab.
Subject:  Plasma kinetics in the inner heliosphere and the NASA Parker Solar Probe mission
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.

I will describe measurements of velocity distribution functions and waves in the solar wind at 1 AU using instruments on NASA's WIND spacecraft and at 0.3 AU using Helios spacecraft. Plasma velocity distributions at 1 AU suggest the evolution by Coulomb collisions from nonthermal states to collisional equilibrium. Measurements at 0.3 AU are generally more nonthermal. This Coulomb coupling relationship can be used probe the plasma distributions of the inner heliosphere and suggests that the coronal population will be highly nonthermal. Furthermore, measurements of plasma waves at 1 AU suggest nonlinear evolution from a population of intense Alfven waves in the inner
heliosphere. Taken together, these observations suggest that the coronal plasma
environment is highly nonthermal and perhaps permeated by impulsive jets or waves. I will also describe the NASA Solar Probe Plus mission which will launch in summer 2018 and orbit the Sun with a final perihelion altitude of 9.8 solar radii, well within the predicted Alfven surface. Parker Solar Probe will make the first ever in situ measurements of plasma heating processes in the solar corona.

Faculty Host: Cynthia Cattell
3:35 pm:
Speaker: C. Kenneth Waters, Department of Philosophy - University of Calgary
Subject: An Epistemology of Scientific Investigation
Refreshments served at 3:15 p.m.

Basic accounts of scientific knowledge typically present it as a system for representing the world, often as a system that represents the fundamental structure of the world. This talk presents science as a system centered on investigating the world. It begins by posing the metaphysical possibility that the world has no fundamental structure. The world seems to have lots of structures, but perhaps it has no overall, general structure that spans scales. The talk continues by examining how geneticists and allied biologists systematically investigate, manipulate, and explain aspects of such a world. It shows that the systematicity of these investigations depends on strategies for manipulating and learning about aspects of parts of the world; it does not depend on scientists having a representation of the overall structure of these parts. The talk concludes that we can dispense with the assumption that the parts of the world investigated by these scientists have a general overall structure to be represented. These parts of the world have lots of structure, and investigation depends on them having lots of structure, but it does not depend on them having a general, overall structure.

4:40 pm:
Speaker: Jian-Ping Wang, University of Minnesota
Subject: To be announced.

Monday, October 30th 2017
12:15 pm:
Speaker: Andrew Matas, UMN
Subject: Testing General Relativity with Gravitational Wave Polarizations

General relativity predicts that gravitational waves should have two helicity-2 polarization states. However, a generic metric theory of gravity allows up to four additional states: two helicity-1 and two helicity-0 modes. Observations of gravitational waves allow tests of this basic prediction of general relativity. In this talk I will review three tests of gravitational wave polarization, using Advanced LIGO and Virgo. First I will discuss a polarization test from GW170814 event. Next, I will discuss tests based on emission from rotating pulsars, which emit continuous, periodic gravitational waves. Finally, I will discuss a search method for a stochastic background of scalar and vector polarizations.

Faculty Host: Vuk Mandic

Tuesday, October 31st 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.

Wednesday, November 1st 2017
10:00 am:
Speaker: Juergen Haase, Felix Bloch Institute for Solid State Physics, University of Leipzig
Subject: Emergence of a new interpretation of NMR of cuprates superconductors

As a fundamental, local, bulk probe nuclear magnetic resonance (NMR) is expected to be at the center of the discussion of the properties of cuprate superconductors. Indeed, in addition to profound insight into chemical structure and bonding, NMR provided vital clues about the electronic spin susceptibility, based on the magnetic hyperfine interaction: the pseudogap (spin gap), single-fluid physics, and spin-singlet pairing were discovered by NMR. However, the data did not appear to contain necessary details for theory. The less often discussed electric hyperfine interaction served a similar chemical purpose, but its understanding in terms of planar charge remained difficult. Here, early on, NMR found that the stoichiometric compounds (Y-1237, Y-1248) appeared to be very homogeneous, as very narrow NMR lines for Cu and O in the CuO_2 plane seemed to prove very small spatial variations of charge. However, all the other materials exhibit mostly broad featureless NMR resonances, indicative rather strong electric field variations in the CuO_2 plane. This conundrum was often considered as proof that charge ordering - apparently not ubiquitous - must be due to chemical inhomogeneity from doping and other crystal imperfections.

Recently, with a number of experiments on different materials we established that a single spin component is not able to explain the NMR shifts, pointing to a different magnetic hyperfine scenario. Very recently, we compiled all literature NMR shift data for planar Cu and with simple plots it becomes already obvious that the hitherto adopted NMR interpretation is wrong, e.g., the magnetic hyperfine scenario is inappropriate. Also recently, we showed that the charges in the plane can be quantified with NMR, which led to the discovery that the sharing of holes between Cu and O (not the doping) is responsible for various cuprate properties, e.g., the maximum T_c . In another set of challenging experiments we just completed a fundamental proof that shows that the above mentioned ‘homogeneous’ materials with sharp NMR lines are in fact highly charge ordered systems, with the order responding to pressure, temperature, and magnetic field. This charge ordering which is ubiquitous to the Y-based systems is likely to be ubiquitous to the CuO_2 plane of all cuprates as it would solve the above mentioned conundrum.

Thus, we view our findings - that will be discussed in more detail - as the emergence of a new interpretation of cuprate NMR, which must have fundamental impact on the understanding of these materials.

Faculty Host: Martin Greven
2:30 pm:
Speaker: Shivaji Sondhi, Princeton University
Subject: Two variations on the theme of operator spreading

Operator spreading refers to the growth of local operators in spatial support and complexity under unitary dynamics. I will discuss some exact results on operator spreading under local random unitary circuits, how they tie into more general beliefs about how operators spread in different settings, and finally how these beliefs constrain the phase space for finding examples of time translation symmetry breaking.

Faculty Host: Fiona Burnell
There will be no seminar this week.
4:30 pm:
CM Journal Club in Tate 201-20
Subject: Quantum tunneling and dynamics in dissipative systems

This week we are going to discuss effects of dissipation on quantum tunneling. The main part of the talk will be devoted to the Caldeira-Leggett model [1], which describes a quantum-mechanical system coupled to an ensemble of oscillators. We will also discuss some specific cases of CL model, which involve two-state systems [2]. The plan of talk is as follows: we first introduce model, discuss experimental relevance and derive general formalism to describe dissipative dynamics. In the second part we will apply this formalism to two-state system and discuss possible applications. Literature: First two references are the renowned papers. The last reference is a good (and very detailed) book on quantum dissipative systems in general.
[1] Caldeira, A. O., & Leggett, A. J. (1983). Quantum tunnelling in a dissipative system. Annals of physics, 149(2), 374-456.
[2] Leggett, A. J., Chakravarty, S. D. A. F. M. G. A., Dorsey, A. T., Fisher, M. P., Garg, A., & Zwerger, W. (1987). Dynamics of the dissipative two-state system. Reviews of Modern Physics, 59(1), 1.
[3] Weiss, U. (2012). Quantum dissipative systems (Vol. 13). World scientific.

Thursday, November 2nd 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Daniel Schmidt, University of Minnesota
Subject: To be announced.
Speaker: Tony Young and Hugh Dickinson
3:35 pm:
Speaker: Shivaji Sondhi, Princeton University
Subject: Statistical Mechanics, Localization and Periodically Driven Quantum Systems

The statistical mechanics of equilibrium systems is characterized by two fundamental ideas: that closed systems approach a late time thermal state and that of phase structure wherein such late time states exhibit singular changes as various parameters characterizing the system are changed. Recent progress has established generalizations of these ideas which apply to periodically driven, or Floquet, closed quantum systems. I will describe this progress, which centrally uses other recent advances in our understanding of many body localization. I will describe how it has resulted in the discovery of entirely new phases such as the Pi-spin glass/Floquet time crystal which exist only in driven quantum system

Faculty Host: Fiona Burnell

Friday, November 3rd 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
12:20 pm:
Speaker: Biqiong Yu, University of Minnesota
Subject: Charge-Density-Wave Correlations and Phonon Anomalies in Cuprates

The recent discovery of CDW order in hole- and electron-doped cuprates has attracted much attention, as there appears to be a close connection between superconductivity and charge-order, and possibly also the mysterious pseudogap phenomenon. A crucial question regarding the nature of the CDW phenomenon in the hole-doped cuprates is whether the observed short-range order is static or associated with dynamic spectral features. We studied the model high-Tc superconductor HgBa2CuO4+δ (Hg1201) via resonant inelastic X-ray scattering (RIXS) at the L3-edge of copper. We measured a single crystal of Hg1201 with Tc = 69K (hole concentration p = 0.083) and constructed energy-momentum RIXS intensity maps, with focus on the CDW momentum transfer, qCDW. The connection between CDW and other low energy excitations (magnons, phonons) will also be discussed.

Speaker: Mark Hertzberg (Tufts U.)
Subject: Lorentz Invariance from Spin 2

In this talk, I study all translationally and rotationally invariant local theories involving massless spin 2 and spin 1 particles that mediate long range forces, allowing for general energy relations and violation of boost invariance. Although gauge invariance is not a priori required to describe non Lorentz invariant theories, I first establish that locality requires a type of soft gauge invariance'. Then by taking the soft graviton limit in scattering amplitudes, I prove that in addition to the usual requirement of universality of couplings, the special relativistic energy formula is also required and must be exact. I contrast this to the case of theories with only spin 1 particles, where, although one can still derive charge conservation from locality, special relativity can be easily violated. I provide indications that the entire structure of relativity can be built up from spin 2 in this fashion. This talk is based on Phys. Rev. D 96, 084048 (2017) arXiv:1704.05071.

Speaker: Ori Fox, Space Telescope Science Institute
Subject: Supernovae, Their Progenitor Systems, and...Kilonovae!
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.

Despite the robust empirical supernova (SN) classification scheme in place, the underlying progenitor systems remain ambiguous for many SN subclasses, particularly stripped-envelope SNe. Mounting evidence over the past decade suggests that the mass loss in a large fraction of these systems occurs due to binary interaction. To date, however, only two binary companions have been detected: SNe 1993J and 2011dh. Here I will present an ongoing observational campaign with the Hubble Space Telescope (HST) to understand SN progenitors and the binary fraction, which has direct implications on the theoretical physics of binary evolution. In contrast, the progenitors of kilonovae are thought to be well known, but a number of questions still exist. While not normally part of my talk, I cannot avoid setting aside some time to discuss the excitement surrounding GW170817, with a focus on HST's contribution to our understanding of the explosion and progenitor system.

Faculty Host: Patrick Kelly
3:35 pm:
Speaker: Darin Hayton, Department of History - Haverford College
Subject: Astrology from University Lecture to Print Culture
Refreshments served at 3:15 p.m.

n 1502 Conrad Tockler became a professor of astrology at the University of Leipzig. Manuscript copies of his lectures on a range of astrological topics and techniques survive as do a number of printed works, ranging from technical treatises on instruments to popular wall calendars and annual prognostications. Tockler’s lecture notes give us a fascinating glimpse into the concrete practices of teaching astrology at the early modern university, while his printed works help us recover the broader uses for astrological literature. Taken together, these materials reveal how Tockler extended a coherent astrological program from the exclusive university lecture hall to wider audiences for printed astrological pamphlets.

Co-sponsored with the Center for Early Modern History and the Center for Austrian Studies

4:40 pm:
Speaker: Cindy Cattell, University of Minnesota
Subject: What can radio waves tell us about particle acceleration in space plasmas ? Satellite and laboratory experiments

Monday, November 6th 2017
12:15 pm:
Speaker: Vihang Mehta, UMN
Subject:  UV Luminosity Functions at the Cosmic High-Noon

Using the Hubble UltraViolet Ultra Deep Field (UVUDF), I investigate the star formation in galaxies at the peak of the cosmic star formation history (around redshift of 2) by using the ultraviolet (UV) light as a tracer for star formation. Particularly, I measure the UV luminosity function (LF) to probe the volume-averaged star formation properties of galaxies at these redshifts. The UVUDF allows for a direct measurement of the faint end slope of the UV LF. This redshift range also provides a unique opportunity to directly compare UV to the "gold standard" of star formation indicators, namely the H-alpha nebular emission line. A joint analysis of the UV and H-alpha LFs suggests that, on average, the star formation histories in low mass galaxies (~10^9 Msol) are more bursty compared to their higher mass counterparts at these redshifts.

Faculty Host: M. Claudia Scarlata

Tuesday, November 7th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Scott Thaller, University of Minnesota
Subject: "First direct observation of modulations in the plasmasphere and large-scale convection electric field driven at the solar rotation period"

Wednesday, November 8th 2017
1:25 pm:
Speaker: Emil Yuzbashyan, Rutgers University
Subject: Quantum Integrability in Systems with Finite Number of Energy Levels

Since the discovery of quantum mechanics, from the Bohr atom and the harmonic oscillator, to the present day, quantum integrable models have played a central role in our understanding of physics at the quantum level. Recently, the field has acquired a new prominence with a range of solid state and cold atom experiments, which demonstrate that integrable systems fail to equilibrate, and thereby defy a conventional statistical description. Roughly speaking, a quantum integrable system is one whose quantum Hamiltonian contains additional integrals of motion beyond the usual total energy and momenta. Yet a complete, unambiguous notion of quantum integrability has long remained elusive, and our understanding of its nonequilibrium and other manifestations is correspondingly incomplete. In the opposite case of chaotic systems, Random Matrix Theory famously provides a tremendously successful analysis of their universal properties. In this talk, I will propose a surprisingly simple and yet unambiguous notion of quantum integrability which leads to a clear explanation and delineation of its various features, culminating in Integrable Matrix Theory: a counterpart of Random Matrix Theory for integrable quantum Hamiltonians.

Faculty Host: Alex Kamenev
Speaker: Zachary Lesko, University of Minnesota
Subject: Using The Drell–Yan process to test accuracy of simulated data sets.

Measurement of the transverse momentum (Qt) of the Z boson is useful for testing the accuracy of simulation software. The hadronization step, which simulates the QCD results of a proton proton collision, is a major potential beneficiary of this study . A highly accurate hadronization is vital for finding the mass of the other weak force carrier, the W boson. However the measurement of the Z's Qt is inaccurate at low values. I will discuss the use of the variable φ∗ which has a high correlation with the Qt of the Z boson

Thursday, November 9th 2017
09:00 am:
Thesis Defense in Tate 201-20
Speaker: Chris Conklin, University of Minnesota
Subject: Electrokinetic Phenomena and Singularity-Driven Flows in Nematic Liquid Crystals
This is the public portion of Mr. Conklin's thesis defense. His advisor is Jorge Vinals.

Electrokinetic phenomena, including electrophoresis and electroosmosis, provide a significant tool for engineering the transport of fluids and particles at microscopic scales. This thesis describes additional mechanisms for generating electrokinetic flow by using a nematic liquid crystal electrolyte. Under an applied electric field the anisotropic properties of the liquid crystal lead to separation of ionic impurities present in the fluid, which couple with the applied field to produce electrostatic forces that drive fluid and particle motion. This force is quadratic in the electric field, implying that systematic flow occurs even in the presence of an oscillating field. This thesis presents numerical and analytical investigations of this electrokinetic mechanism. We show that the charge density and fluid velocity of a system depends strongly on the topology of the liquid crystal orientation, and we present results for several distinct configurations, including periodic distortions, isolated disclinations, and particle suspensions. We also show that liquid crystal electrokinetic systems can be designed to mimic the behaviors of active nematics -- collections of particles which can self-propel along a particular direction.

10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Paul Francois, McGill University
Subject: Untangling the biological hairball of immune recognition networks

Complex mathematical models of interaction networks are routinely used for prediction in systems biology. However, it is difficult to reconcile network complexities with a formal understanding of their behavior. I will introduce several models of immune recognition by T cells and will show how a simple procedure can be used to reduce them to functional submodules, using statistical mechanics of complex systems combined with a fitness-based approach inspired by in silico evolution. Our procedure works by putting parameters or combination of parameters to some asymptotic limit, while keeping (or slightly improving) the model performance, and requires parameter symmetry breaking for more complex models. An intractable model of immune recognition with close to a hundred individual transition rates is reduced to a simple two-parameter model, and connected to the adaptive sorting" principle that we previously identified and experimentally validated. Our procedure extracts three different mechanisms for early immune recognition, and automatically discovers similar functional modules in different models of the same process allowing for model classification and comparison.

11:00 am:
Speaker: Alexey V. Kimel, Radboud University, Institute for Molecules and Materials, Nijmegen, The Netherlands
Subject: Cold opto‐magnetic recording at the edge of time
Please note time and room change for this seminar.

The ability to switch magnets between two stable bit states is the main principle of modern data storage technology. Controlling the magnetic state of media with the lowest possible dissipations and simultaneously at the fastest possible time‐scale is a new and great challenge in fundamental and applied magnetism. A femtosecond laser pulse is one of the shortest stimuli in contemporary condensed matter physics. Exciting magnets on a timescale much faster than characteristic times of atomic, orbital and spin motion can steer magnetization dynamics along yet unexplored non-thermodynamic routes. In my talk I would like to discuss these routes for the cases of magnetic dielectrics [1‐3] and propose ways to design a medium for ultrafast and cold opto‐magnetic recording.

Reference: [1] D. Afanasiev, et. al. , Phys. Rev. Lett. 116, 097401 (2016). [2] S. Baierl, et. al., Nature Photonics 10, 715 (2016). [3] A. Stupakiewicz, et.
al, Nature 542, 71–74 (2017).

Faculty Host: Mo Li
Speaker: Avery Garon and Larry Rudnick
3:35 pm:
Speaker: Stan Brodsky, SLAC
Subject: Physics on the Light Front: A Novel Approach to Quark Confinement and QCD Phenomena

I will survey a number of exciting new developments in hadron and nuclear physics which can be derived from the underlying conformal properties of quantum chromodynamics and the application of Dirac's boost-invariant light-front quantization. These include new insights into the origin of the QCD mass scale and the physics of quark confinement, as well as surprising supersymmetric relations between the masses of mesons, baryons, and tetraquarks. I also will discuss a number of novel features of QCD, such as color transparency, hidden color, intrinsic heavy quark phenomena, and factorization-breaking lensing effects.

Faculty Host: Keith Olive

Friday, November 10th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
12:20 pm:
Speaker: Mengqun Li, University of Minnesota
Subject: Magnetic excitations in Z2 vortex crystals

Z2 vortex crystals have been recently shown to be
realized in triangular Kitaev-Heisenberg systems. These Z2 vortices are
stabilized by spin-orbit coupling introduced via the Kitaev term in the
Hamiltonian. Here, we analyze the magnetic excitations of these Z2 vortex
crystals and investigate the spin wave spectrum, energy gap and
dynamical spin structure factor in terms of the interplay between the
Kitaev and isotropic Heisenberg interaction.

Speaker: Stan Brodsky (SLAC)
Subject: Supersymmetric Features of Hadron Physics and other Novel Properties of Quantum Chromodynamics from Light-Front holography and Superconformal Algebra

Speaker: No colloquium this week.
3:35 pm:
Speaker: Rob DiSalle, Department of Philosophy - Western University
Subject: Absolute Space, Relative Motion, and the Method of Newtonian Physics
Refreshments served at 3:15 p.m.

Philosophical discussions of Newton’s theory of absolute space and motion generally focus on metaphysical questions that were raised by philosophical critics, such as Leibniz, who emphasized the relativity of motion. Such discussions generally overlook the fact that, in the course of developing his dynamics, Newton himself pursued the problem of the relativity of motion further than his opponents realized. While they defended the relativity of motion as a general principle, only Newton developed what ought to be called a theory of relativity: a systematic theoretical account of what is objective in the description of physical interactions, and a principled distinction between the objective properties and those that depend on the choice of a frame of reference. On this basis Newton articulated, more clearly than his contemporaries, the conceptual revisions imposed by the relativity of motion on prevailing notions of force, inertia, and causality. Indeed, the history of his thinking shows that Newton introduced the theory of absolute space precisely in order to articulate his theory of relativity, and to apply it to the outstanding problem of “the frame of system of the world.

4:40 pm:
There will be no seminar this week.

Monday, November 13th 2017
12:15 pm:
Speaker: Karl Young, UMN
Subject: Optical Design of PICO - The Probe of Inflation and Cosmic Origins

The Probe of Inflation and Cosmic Origins (PICO) is a mission concept study for a Probe-class NASA mm-wave satellite. By mapping the full sky in temperature and polarization, PICO would probe the physics of the Big Bang and the energy scale of inflation, constrain the sum of neutrino masses and measure the growth of structure, map the history of reionization, and shed new light on the role of magnetic fields in galactic evolution and star formation. I will present the current optical design of PICO and discuss the design process that led to this version. Additionally I will present a white noise model of the instrument and estimated mission sensitivity.

Faculty Host: Shaul Hanany

Tuesday, November 14th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Jenna Samra, CFA, Harvard
Subject: Eclipse Science Results from the Airborne Infrared Spectrometer (AIR-Spec)

On August 21, 2017, the Airborne Infrared Spectrometer (AIR-Spec) observed the total solar eclipse at an altitude of 14 km from aboard the NSF/NCAR Gulfstream V research aircraft. The instrument successfully observed the five coronal emission lines that it was designed to measure: Si X (1.43µm), S XI (1.92µm), Fe IX (2.85µm), Mg VIII (3.03µm), and Si IX (3.94µm). The Fe IX observation is likely the first of this line. The linewidths, peak intensities, and center wavelengths of all five lines were measured radially outward from the limb at four positions in the corona. One of the positions sampled a prominence, where a number of H I lines were also observed. The telluric absorption at 14 km was significant near some of the lines, which has implications for future ground-based infrared instruments. Several follow-on experiments are being proposed to expand on the results from the 2017 eclipse. These include a re-flight of AIR-Spec during the 2019 total eclipse, development of a spectropolarimeter operating at AIR-Spec wavelengths, and a laboratory study of infrared coronal emission lines.

3:30 pm:
CM Journal Club in Tate 301-20
Speaker: Morten Christensen
Subject: The physics of quantum materials

The paper to be discussed is The physics of quantum materials by B. Keimer and J. E. Moore. Reading it before the journal club meeting is strongly encouraged.
https://www.nature.com/nphys/journal/v13/n11/full/nphys4302.html

4:30 pm:
Speaker: To be announced

Wednesday, November 15th 2017
1:25 pm:
Speaker: Cory Dean, Columbia University
Subject: Graphene in the extreme quantum limit

Soon after the discovery of monolayer graphene, it was shown that bilayer graphene (BLG), consisting of two bernal stacked monolayers, could theoretically support an even-denominator fractional quantum Hall state equivalent to the 5/2 Moore-Read Pfaffian first identified in GaAs . Owing to the unique landau level spectrum in BLG, the Pfaffian in this system is expected to be tunable by electric and magnetic fields, with the potential to be stronger than in GaAs for accessible field parameters. In my talk I will discuss recent magnetotransport studies of high mobility, BLG. Utilizing a dual gate geometry to tune through different orbital and layer polarizations, we find four even denominator states appearing within the N = 1 orbital branches of the lowest LL. We investigate how these states evolve with varying parameters and provide the first mapping of the B – D phase diagram. Our results confirm the unique tunability of the even denominator state in BLG, and we reach a regime where the energy gap is found to exceed several kelvin. I will also present recent measurements of bilayer systems in which we separate the two layers by a thin BN spacer. Here, by tuning the interlayer interaction strength via the layer separation, we are able to stabilize new correlated states in the double layer systems formed from interlayer excitons.

Faculty Host: Boris Shklovskii
Speaker: Dr Jason Bono from Fermilab
Subject: To be announced.

Thursday, November 16th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Bo Huang UCSF, Pharmaceutical Chemistry
Subject: Watching in the inner life of a cell: beyond super-resolution microscopy

Cellular processes are orchestrated by a large number of biomolecules in a spatially and temporally coordinated manner within a tiny volume. To uncover the underlying organizational principles and their functional relevance, we take microscopy visualization as the primary approach to map the spatial localization, temporal dynamics and activity profiles of proteins and nucleic acids. We have used super-resolution microcopy to dissed the molecular organization of the cilium transition zone, revealing its function as a gate of ciliary trafficking. We have also been developing techniques for the mapping of the physical organization of the genome in the nucleus.

Speaker: Huaqing Mao
3:35 pm:
Speaker: Cory Dean, Columbia University
Subject: From 3D to 2D and Back Again
Note the room change for this week only

Graphene , a single layer of carbon atoms arranged in a hexagonal lattice, is probably the best known, and most extensively characterized two-dimensional material. However, this represents just one of a larger class of van der Waals materials, in which atomic monolayers can be mechanically isolated from the bulk. By integrating these materials with one another, an exciting new opportunity has emerged in which layered heterostuctures can be fabricated with properties beyond those of the constituent materials. In this talk I will present some of our recent efforts where, by tuning the geometry of these heterostructures at the nanoscale, we are able to realize yet a new level of control over their electronic properties.

Faculty Host: Boris Shklovskii
4:30 pm:
Climate and Diversity Meet and Greet in Tate Hall, Church Street Lobby
Subject: Introduction and Information gathering session
Refreshments will be served.

Meet the committee
Find out what we're doing and how we can serve you
Give us feedback and suggestions

What you'll find at our tables:

Topic 1: Resources
This table will describe some of the resources available to faculty, researchers, staff, and students campus-wide and within our own School. Stop by and take a handout or fill out a survey, and get to know the members of the School’s Climate and Diversity Committee.

Topic 2: School of Physics and Astronomy climate
These tables will solicit feedback from graduate students on climate issues within the school and describe our upcoming poster campaign.
We will also have representatives from WIPA, GradPhi, SPS, and WISE to provide information about their events and organizations and ways that they provide support.

Topic 3: Inclusiveness
This table will provide information on workshops, training programs, and involvement opportunities available to help all members of the community to better understand and support each other.

Climate and Diversity Website: http://climate-diversity.physics.umn.edu/

Friday, November 17th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Zewei Xiong, University of Minnesota
Subject: Active-sterile neutrino oscillations in the neutrino-driven wind
12:20 pm:
Speaker: Sajna Hameed
Subject: Neutron Scattering Study of the Magnetic Phase Transition in Rare-Earth Titanates

The Mott-insulating rare-earth (R) titanates (RTiO3) are known to exhibit a ferromagnetic-antiferromagnetic transition as the Ti-O-Ti bond angle increases in the GdFeO3-type distorted perovskite structure. Evidence for a similar transition at a critical doping xc~ 0.3 has been found in the solid-solution system Y1-xLaxTiO3. Although neutron scattering has been used to study the magnetic response of single crystals of the parent compounds YTiO3 and LaTiO3, such studies have not been reported for the solid solution. Here we report on our neutron scattering work on the magnetic order and excitations in doped system Y1-xLaxTiO3.

Speaker: Ben von Harling (DESY)
Subject: Electroweak baryogenesis in composite Higgs models

Electroweak baryogenesis is an appealing scenario in which the baryon
asymmetry of the universe is generated during the electroweak phase
transition. However, in the standard model it fails because the phase
transition is not first order. And even if it were, the amount of
CP-violation is also not enough to generate the observed asymmetry. In
this talk, I discuss how these problems can be solved in the context
of composite Higgs models. The electroweak phase transition can be
sufficiently strong if it happens simultaneously with the confining
phase transition of the composite Higgs sector. Furthermore, enough
CP-violation for successful electroweak baryogenesis can arise if the
Yukawa couplings vary during the phase transition.

Subject:  How to Reionize the Universe - Clues from the Low-Redshift Green Pea Galaxies
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.

Reionization represents a fundamental transition in the universe’s properties, and yet, we know little about how it occurred. The most likely explanation is that Lyman continuum (LyC) radiation escaped into the intergalactic medium from early star-forming galaxies. However, most star-forming galaxies show no signs of LyC escape. Recently, the "Green Pea" galaxies have emerged as the first known star-forming galaxy population where strong LyC escape is common. I will discuss what we are learning from the Green Peas about ways to identify LyC-leaking galaxies, the role of feedback in LyC escape, and the properties of LyC-emitters.

Faculty Host: M. Claudia Scarlata
3:35 pm:
Speaker: Molly Kao, Department of Philosophy - University of Montreal
Subject: Unification and Heuristic Strategies in the Development of Quantum Theory
Refreshments served at 3:15 p.m.

In this talk, Dr. Kao provides a heuristic conception of the feature of unification in the context of developing scientific theories. She argues that the value of a unifying hypothesis is not necessarily that of its ability to explain phenomena, nor must it be that it is more likely to be true. Instead, unifying hypotheses can be valuable because they guide experimental research in different domains in such a way that the results from those experiments contribute to our understanding of a theory under pursuit. Dr. Kao supports this characterization by appealing to the early development of quantum theory.

4:40 pm:
Speaker: Woods Halley, University of Minnesota
Subject: Origin of Life: A problem in nonequilibrium statistical mechanics.

Monday, November 20th 2017
12:15 pm:
Speaker: Allison Noble, MIT, Kavli Institute
Subject: Dissecting z>1 Galaxy Clusters: Studying Star Formation from the Outskirts to the Core

Understanding the influence of environment on baryonic processes is a fundamental goal in studies of galaxy evolution, and galaxy clusters offer ideal laboratories with which to examine environmental effects on their constituent members. Clusters continually evolve and build up mass through the accumulation of galaxies, resulting in distinct galaxy populations based on their accretion history. I will discuss using cluster phase space (line-of-sight velocity versus projected clustercentric radius) as a way to probe the accretion histories of cluster galaxies to study environmental effects on star formation at z~1. I will also present recent ALMA observations of massive gas reservoirs in z=1.6 cluster galaxies. The raw fuel of star formation, molecular gas is typically absent in low-redshift cluster galaxies; with these new ALMA data, we are witnessing the first direct evidence that gas-rich galaxies are located indistinguishably in both the field and clusters at high-redshift.

Faculty Host: Lawrence Rudnick

Tuesday, November 21st 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Aaron Breneman, University of Minnesota
Subject: Observations directly linking relativistic electron microbursts to whistler mode chorus: Van Allen Probes and FIREBIRD II

We present observations that provide the strongest evidence yet
that discrete whistler mode chorus packets cause relativistic electron microbursts.
On Jan 20th, 2016 near 1944 UT the low Earth orbiting CubeSat FIREBIRD
II observed energetic microbursts (near L=5.6 and MLT=10.5) from its lower
limit of 220 keV, to 1 MeV. In the outer radiation belt and magnetically conjugate,
Van Allen Probe A observed rising-tone, lower band chorus waves with
durations and cadences similar to the microbursts. No other waves were observed.
This is the first time that chorus and microbursts have been simultaneously observed
with a separation smaller than a chorus packet. A majority of the microbursts
do not have the energy dispersion expected for trapped electrons bouncing between
mirror points. This confirms that the electrons are rapidly (nonlinearly)
scattered into the loss cone by a coherent interaction with the large amplitude
(up to ∼900 pT) chorus. Comparison of observed time-averaged microburst flux
and estimated total electron drift shell content at L=5.6 indicate that microbursts may represent a significant source of energetic electron loss in the outer radiation
belt.

12:20 pm:
Speaker: Alexander Kuntsevich, P. N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow, Russia
Subject: Spin magnetization and entropy measurements in two-dimensional systems

We apply recharging technique to measure derivatives dS/dn and dM/dn (S and and M are the entropy and the magnetization per unit area, n is the carrier density) in two-dimensional gated systems. In particular, we demonstrate that 2D metal-to-insulator transition is accompanied by formation of spin droplets. We also detect fingerprints of these droplets in transport properties of the system. Entropy measurements reveal signatures of electron-electron interactions in both Fermi liquid (T<< E_F) and correlated plasma (T~E_F) regime. In the quantum Hall effect gaps, entropy decreases significantly. In the Fermi-liquid regime (high densities)S goes to zero as temperature decreases as S \propto T, thus independently checking the 3rd law of thermodynamics.

Wednesday, November 22nd 2017
Speaker: Hajime Muramatsu, University of Minnesota
Subject: Leptonic Decays of Charmed Mesons at BESIII

BESIII now holds the world's largest e+e- annihilation samples taken at Ecm = 3.773 and 4.178 GeV which produce copious charmed mesons, D0, D+, and Ds+. In this talk, I would like to report our on-going studies on D+ -> l nu and
Ds -> l nu (l = mu and tau). These allow us to determine the elements of the CKM matrix within the standard model, to test the unitarity of the second rows of the CKM matrix, probe lepton universality, as well as to calibrate the LQCD calculations of the decay constants, fD(s)+.

Thursday, November 23rd 2017
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week (Thanksgiving Break)
Speaker: No Journal Club - Thanksgiving holiday
3:35 pm:
Speaker: There will be no colloquium this week due to Thanksgiving

Friday, November 24th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week (Thanksgiving Break)
12:20 pm:
There will be no seminar this week (Thanksgiving Break)
Speaker: NO SEMINAR (THANKSGIVING)
Speaker: No colloquium - Thanksgiving Holiday
3:35 pm:
There will be no seminar this week (Thanksgiving Break)
4:40 pm:
There will be no seminar this week (Thanksgiving Break)

Monday, November 27th 2017
12:15 pm:
Speaker: Nader Mirabolfathi, Texas A&M University
Subject: From Single-Electron Resolution Phonon-Mediated Detectors To Directional Dark Matter Searches
THIS SEMINAR IS CANCELLED due to illness - To be rescheduled next semester

Direct detection dark matter experiments are striving to develop technologies that allow for ultra low-threshold large modular mass detectors. After a brief overview of the current efforts in the field, I will discuss our new studies suggesting that at the quantum electronic excitation level, solid state detectors exhibit significant directional sensitivity to DM interactions. The solar neutrino-nucleus elastic coherent scattering will soon become the irreducible background for direct detection experiments. Directional sensitivity offers a solution to further gain in DM sensitivity beyond this so called "neutrino floor".

Faculty Host: Priscilla Cushman
1:25 pm:
Speaker: Rajan Gupta, LANL
Subject: Probing TeV physics with precision calculation of nucleon Structure using lattice QCD.
Note change in time and day for the Nuclear Seminar, this week only.

This talk will present a number of high precision results on matrix
elements of quark bilinear operators between nucleon states using
lattice QCD. From these, we extract a number of exciting quantities,
at the intersection of nuclear and particle physics. We show that the
accuracy with which axial charge gA , a fundamental parameter encapsulating the weak interaction of nucleons, can be calculated. Results for the scalar and tensor charges, g_S and g_T, which combined with precision neutron decay distribution probe novel scalar and tensor interactions at the TeV scale. Vector form factors are probed in electron scattering, while axial vector form factors are used in the calculation of the cross-section of neutrinos on nuclear
targets. These energy dependent cross-sections are needed to determine the neutrino flux, an important systematic in neutrino oscillation experiments. Finally we will present results for flavor diagonal charges that provide the contribution of the quark spin to the nucleon spin, the quark EDM to the neutron EDM, and needed to determine the cross-section of dark matter with nuclear targets.

Tuesday, November 28th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Sheng Tian, University of Minnesota
Subject: The flow of Poynting flux into the terrestrial cusp and auroral zone and its role in powering energy intensive collisionless acceleration mechanisms
4:30 pm:
Speaker: Guichan Yu, University of Minnesota
Subject: Precursor of superconductivity in the normal state of cuprates

Wednesday, November 29th 2017
Speaker: Marvin Marshak, University of Minnesota
Subject: Neutrino Experiments at the Soudan Underground Laboratory

I will discuss the 38-year history of proton decay and neutrino experiments
at the Soudan Underground Laboratory, with a focus on the early history
of how and why the lab started and how it developed an extensive program
of physics experiments.

4:30 pm:
CM Journal Club in Tate Hall 201-20
Speaker: Mengxing Ye
Subject: Deconfined quantum criticality

I will give an overview of the theory of deconfined quantum criticality following [1]. As an example, it shows that the quantum phase transition of the S=1/2 square lattice antiferromagnet between the Neel state (which breaks spin rotation symmetry) and the paramagnetic valence bond crystal (which preserves spin rotation but breaks lattice symmetry) is second order without fine-tuning. To achieve it, the field theory at the quantum critical point cannot be described by order parameters of either phases. I will focus on the physical picture and briefly discuss how the low energy field theory is formulated. A look at the less technical overview paper [2] is recommended.

7:00 pm:
Speaker: Philip Kim, Harvard University
Subject: Stacking atomic layers: quest for new materials and physics
Refreshments in atrium after the lecture .

Modern electronics has been heavily relied on the technology to confine electrons in the interface layers of semiconductors. In recent years, scientists discovered that various atomically thin materials including graphene, a single atomic carbon layer, can be isolated. In these atomically thin materials, quantum physics allows electrons to move only in an effective 2-dimensional (2D) space. By stacking these 2D quantum materials, one can also create atomic-scale heterostructures with a wide variety of electronic and optical properties. I will discuss the creation of new heterostructures based on atomically thin materials and emerging new physics with technological implications therein.

Thursday, November 30th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: David Odde, University of Minnesota
Subject:  Simulating cell migration

David Odde, University of Minnesota Cell migration is key to many biological processes including embryonic development, wound healing, and disease progression. Recent studies have shown that cell migration is sensitive to microenvironmental stiffness, and many cells display a stiffness optimum at which migration is maximal. To create a unified theoretical framework for cell migration, we have now developed and experimentally tested a whole cell migration simulator based on the motor-clutch model of cellular force transmission by imposing coupled force balances and mass balances on molecular motors, adhesion molecules (“clutches”), and actin subunits in a compliant microenvironment. The model predicts a stiffness optimum that can be shifted by altering the number of active molecular motors and clutches. This prediction was tested experimentally using glioma (brain cancer) cells, and we find that the motor-clutch cell migration simulator provides a theoretical framework with which to predict cell adhesion and migration in defined mechanochemical microenvironments in 1D, 2D, and 3D.

Speaker: Vihang Mehta and Tom Jones
3:35 pm:
Speaker: Philip Kim, Harvard University
Subject: Unusual quasiparticle correlation in graphene
Fall 2017 Van Vleck Lecturer

Interactions between particles in quantum many-body systems can lead to a collective behavior. In a condensed matter system consisting of weakly interacting particles, a propagating particle interacting with its surroundings can be viewed as a ‘dressed’ quasiparticle with renormalized mass and other dynamic properties. The lack of screening enables strong Coulomb interactions between charged particles, leading to new collective dynamics. In this talk, I will discuss three examples concerning strongly interacting quasiparticles in graphene. In the first example, it will be shown that the thermally populated electrons and holes to realize Dirac fluid, where a huge violation of Wiedemann-Franz law is observed. The second example is realizing magnetoexcitons to correlated the quasiparticles in quantized Landau levels to form magnetoexcitons, which can condense into Bose-Einstein condensation. Finally, we will also discuss another way of correlated quasi-particles in graphene using superconducting proximity effect. Here, we employ the crossed Andreev reflection across thin type II superconducting electrodes to correlated spatially separated quasiparticles. Under strong magnetic fields, the quantum Hall edge states can carry these quasiparticles.

Friday, December 1st 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
The Nuclear seminar will be held on Monday this week.
12:20 pm:
Speaker: Protyush Sahu
Subject: Spin Hall magnetoresistance in W/CFB bilayers
To be announced.

Heavy metal/ferromagnet (HM/FM) bilayers have garnered a lot of attention in recent years, owing to the rise of spintronics. These systems are central to the study of spin-orbit torque, originating from the interaction between spin polarized electrons from HM and magnetization of FM. This interaction can produce change in resistance of the device, which is strongly dependent on the relative orientation between electron spin and the magnetization, called spin Hall magnetoresistance (SMR). The relative change in MR is theoretically predicted to be strongly dependent on the spin Hall effect (SHE) in HM and the magnetic properties of FM. SHE in W is strongly dependent on the crystal phase, which was characterized by X-ray diffraction. We study and characterize SMR in Tungsten(W)/CoFeB(CFB) bilayers with perpendicular magnetic anisotropy at different thermal annealing temperatures using two different experimental technique. Stoner-Wolfharth model was used to explain deviations in our experimental data from the predicted behavior.

Speaker: Vitaly Vanchurin (UMN Duluth)
Subject: General Relativity from Non-Equilibrium Thermodynamics of Quantum Information

In this talk I will argue that general relativity may be viewed as a useful limit of quantum mechanics with many degrees of freedom, very much like thermodynamics is a useful limit of classical mechanics with many degrees of freedom. First, I will construct statistical ensembles of ket-vectors using spatially covariant dual field theories with a metric tensor playing the role of a conjugate thermodynamic variable to the so-called information tensor (which is related to both Fisher matrix and Fubini-Study metric). Secondly, I will analyze evolution of the ensembles of ket-vectors to argue that an approximate space-time covariance of the dual field theories can be achieved if certain quantum computational complexities are minimized. And finally, I will show that minimization of a non-equilibrium entropy production can lead to the Einstein-Hilbert dynamics of the metric tensor for a particularly simple and highly symmetric form of the Onsager tensor.

Speaker: Shea Brown, U of Iowa
Subject: Astrophysical Machine Learning: Applications for the next generation all-sky surveys
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.

Machine learning is playing an ever increasing role in astrophysics, due in part to the large number of all-sky astronomical surveys that are being carried out in this decade. Massive data-rates make it effectively impossible for humans to individually inspect all the data, so we must rely on "intelligent" algorithms to classify scientifically relevant and exciting sources. I will highlight a few areas where machine learning, and in particular deep-learning, can play a significant role in upcoming surveys at radio wavelengths, leading up to the planned Square Kilometre Array.

Faculty Host: Lawrence Rudnick
3:35 pm:
Speaker: Nora Berenstain, Department of Philosophy - University of Tennessee-Knoxville
Subject: Active Ignorance and the Rhetoric of Biological Race Realism
Refreshments served at 3:15 p.m.

Biological race realism is frequently assumed in scientific investigations into presumed connections between race and physical and psychological features such as intelligence, temperament, criminality, and athleticism. I analyze ways scientists and philosophers actively cultivate ignorance surrounding biological race science by using rhetorical tools to portray critiques of biological race realism as in opposition to science itself. These rhetorical strategies involve painting substantive scientific criticisms—such as questions about empirical and methodological issues with data interpretation, unjustified background assumptions, and failure to rule out alternative explanations of data—as motivated purely by ideological concerns. These rhetorical strategies invoke an assumed distinction between epistemic and non-epistemic values in science and misrepresent criticisms of biological race realism as existing wholly outside the realm of epistemic values.

4:40 pm:
Speaker: Bob Lysak, University of Minnesota
Subject: Alfven Waves and the Aurora

Monday, December 4th 2017
12:15 pm:
Speaker: Larry Rudnick, UMN
Subject: Line (searches) from the EOR - an update

There are a wide variety of experiments underway or planned to probe H and molecular emission from the EOR, to determine the structure and evolution of ionization. I will provide an update on current limits and prospects over the next five years.

1:00 pm:
Thesis Defense in Akerman 317
Speaker: Sheng Tian, University of Minnesota
Subject: The flow of Poynting flux into the terrestrial cusp and auroral zone and its role in powering energy intensive collisionless acceleration mechanisms
This is the public portion of Mr Tian's thesis defense. His advisor is John Wygant.

Tuesday, December 5th 2017
11:15 am:
Space Physics Seminar in Tate 301-20
Speaker: AGU Practice Talks
Note change of time, this week only.

Wednesday, December 6th 2017
1:25 pm:
Speaker: Mark Bowick, KITP, Santa Barbara
Subject: Facets of Order

What determines shape? Energy minimization in flexible systems with competition between order and shape change can lead to a wide variety of shapes including highly faceted singular structures. I will discuss the shape of molecularly-thin vesicles with liquid crystalline order.

Faculty Host: Boris Shklovskii
4:30 pm:
CM Journal Club in Tate 201-20
Speaker: Bo Xiong
Subject: Topological field theory treatment to quantum hall liquids

Following Ref.[1] and [2], I am going to introduce the approach of Chern-Simons theory to quantum hall liquids, focusing on fractional quantum hall effect. Classification of Abelian quantum hall states will be given at the end.

[1] Zee, A. "Quantum hall fluids." Field theory, topology and condensed matter physics. Springer, Berlin, Heidelberg, 1995. 99-153.
[2] Wen, Xiao-Gang. "Topological orders and edge excitations in fractional quantum Hall states." Advances in Physics 44.5 (1995): 405-473.

Thursday, December 7th 2017
08:00 am:
Untitled in Physics
To be announced.
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Renee Frontiera, University of Minnesota
Subject: Towards label-free super-resolution imaging

Super-resolution imaging methods have revolutionized our understanding of biological processes on nanometer length scales, due to their ability to break the optical diffraction limit. These new techniques enable direct visualization of fluorescently-labeled samples on the 10 nm length scale. However, the fluorescent labels required by current super-resolution imaging approaches can be perturbation to structure and function, and fluorophores are prone to significant photobleaching. Thus, we have developed a novel super-resolution imaging technique which does not require the use of fluorescent labels, based on chemically-specific Raman imaging. We combine stimulated Raman microscopy with concepts from stimulated emission depletion microscopy to achieve label-free sub-diffraction imaging. This talk will cover the photophysical principles behind super-resolution Raman imaging, highlight the highest resolution achieved to date, and discuss biological applications of the technique, particularly with respect to imaging nanoscale cellular membrane dynamics.

Speaker: Sharan Banagin and Claudia Scarlata
3:35 pm:
Speaker: Mark Bowick, KITP Santa Barbara
Subject: Fragile Objects: The Hard Science of Soft Matter

The natural and synthetic world has an extremely rich variety of states of matter. Many of these are fragile structures that are both flexible and complex and they range from atomic in scale to the very large. I will present four vignettes from the world of fragile objects (soft matter) that illustrate their counter-intuitive behavior and the intellectual challenge they present. I will demonstrate how the concept “state of matter” is often not as simple as one might think and show how fluctuations can lead to rather surprising behavior.

Faculty Host: Boris Shklovskii

Friday, December 8th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Ming Li, University of Minnesota
Subject: Towards the Hydrodynamic Evolution of the High Baryon Density Matter at the Forward Rapidity of High Energy Heavy-Ion Collisions.

In high energy heavy-ion collisions, for collision energy attainable at RHIC and LHC, we previously showed that high baryon density matter (more than ten times larger than normal nuclear density) can be achieved in the fragmentation regions at the early stage. Considering the large energy density and the high baryon density, it is reasonable to assume these matter can thermalize just as what had happened in the central rapidity region. The subsequent time evolution of these matter will follow the principle of fluid dynamics. In this talk, I will present my results on implementing the Central-Upwind scheme (a.k.a the Kurganov-Tadmor scheme used by MUSIC ) in numerically solving the 1+1D relativistic ideal hydrodynamic equations with the high baryon density initial condition mentioned above. This is the first step towards the inclusion of baryon diffusion effects in the hydrodynamic evolution of the high baryon density matter.

12:20 pm:
Speaker: Zach Anderson, University of Minnesota
Subject: Inelastic neutron scattering measurements of antiferromagnetic excitations in HgBa2CuO4+δ

Unconventional superconductivity and antiferromagnetism often appear close to each other in the phase diagrams of the cuprates and other unconventional superconductors, and it has been proposed that antiferromagnetic (AF) correlations drive the pairing underlying unconventional superconductivity. A quantitative understanding of these correlations is therefore of great importance. We studied AF excitations in the cuprate superconductor HgBa2CuO4+δ (Hg1201) using inelastic neutron scattering. The structural simplicity of Hg1201 makes it an ideal system in which to study the physics of the essential copper-oxygen plane. Our neutron scattering results differ qualitatively from what is seen in other cuprates, suggesting that structural complications in other materials significantly alter the AF excitations.

Speaker: Matthew Johnson (Perimeter Institute and York University)
Subject: Understanding the Ultra Large Scale Structure of the Universe through observation and theory

Anomalies in the CMB on large angular scales could find an explanation in terms of pre-inflationary physics or intrinsic statistical anisotropies. However, due to cosmic variance it is difficult to conclusively test many of these ideas using the primary cosmic microwave background (CMB) alone. In this talk, I will outline a program to place stringent observational constraints on theories that predict ultra-large scale structure or statistical anisotropies using the Sunyaev Zel'dovich effect and tracers of large-scale structure. These methods will become accessible with next-generation CMB experiments and planned galaxy surveys. I will forecast constraints on novel models in the scalar and tensor sectors. The prospect of better observations makes it important to deliver precise predictions on the theory side. I will end by briefly describing efforts to connect pre-inflationary physics to observation using numerical relativity.

Speaker: Jeremy Webb, Indiana U
Subject: Do Globular Clusters Have an Identity Problem? - The Dynamics of Mass Segregation and Tidal Stripping
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.

Globular clusters, once thought to be simple dynamical systems, are proving to be increasingly complex as our observational capabilities continue to grow. Advancements in ground based telescopes in particular have made it possible to study how various cluster properties change as a function of clustercentric distance, as such studies require multiple pointings per cluster. Being able to study the radial dependence of cluster properties allows for the internal dynamical evolution of clusters to be directly probed. Of particular interest is the ability to measure the degree of mass segregation in a cluster as it provides an indication of a cluster's dynamical age. Coupled with estimates of how much mass a cluster has lost since formation, based on its global mass function, it becomes possible to begin piecing together each cluster's dynamical history. In this talk, I will first present a new method for quantifying the degree of mass segregation in a cluster based on the radial variation of its mass function and relate this measurement to a cluster's kinematic properties. I will then illustrate the application of this method to select Milky Way Globular Clusters and discuss how the degree of mass segregation within a cluster is inconsistent with its present day mass function. Potential remedies to this discrepancy will also be discussed.

Faculty Host: Liliya L.R. Williams
3:35 pm:
Speaker: Andy Bruno
Subject: Eurasianism in Soviet Science: The Environmental Views of Aleksandr Fersman
Refreshments served at 3:15 p.m.

Thoroughly a product of imperial Russia’s aristocratic culture, the mineralogist and geochemist Aleksandr Fersman rose to the top of the country’s scientific establishment after the Bolsheviks took control. He then remained a staunch supporter of various industrial projects through much of the Stalinist period. This talk puts Fersman’s thinking about the natural world in conversation with a quite distinctive mode of intellectual inquiry that developed contemporaneously. Eurasianism was a philosophical doctrine of a group of Russian émigrés who emphasized Russia’s unique status straddling Europe and Asia. While Fersman did not belong to this group of thinkers, a number of his ideas drew on specific experiences in the environments of the Eurasian landmass. Indeed, I argue that Fersman’s dualistic understanding of nature, his advocacy for the field of geochemistry, his definition of deserts, and a scheme he proposed for industrial operations owed much to the Eurasian settings of the science he practiced. Furthermore, this case of a Eurasian mineralogist illuminates novel aspects of the interplay between national and global sciences.

4:40 pm:
Speaker: To be announced.

Monday, December 11th 2017
12:15 pm:
Speaker: Patrick Kelly, UMN
Subject:  Using A Highly Magnified Star and the Multiply Imaged Supernova Refsdal to Constrain the Outcomes of Star Formation, Stellar Evolution, and the Abundance of Primordial Black Holes

We recently detected an individual blue supergiant star in a multiply imaged spiral galaxy at redshift z=1.49 behind the MACS J1149 galaxy cluster (z=0.54). In the spring of 2016, the star (dubbed LS1) appeared to brighten by a factor of three in Hubble Space Telescope imaging due to microlensing by a star in the intracluster medium of the foreground cluster. Lens models of the cluster show that the star, which is adjacent to the galaxy cluster’s critical curve, likely became magnified briefly by more than a factor of 2000. Additional monitoring subsequently revealed a second transient object which may be LS1’s counterimage in October 2016. I will describe ongoing work to model LS1’s light curve and to draw conclusions about the stellar population in the intracluster medium, the outcomes of massive stellar evolution, and the abundance of primordial black holes. The multiply imaged supernova, SN Refsdal, has appeared as five separate images, and a new measurement of its time delay provides useful and complementary constraints on the cluster lens model.

1:25 pm:
Nuclear Physics Seminar in Tate 201-20
Speaker: Huaiyu Duan
Subject: Fast neutrino oscillations in supernovae
(Note Special Time)

Neutrinos dominate the energetics of core-collapse supernovae and are crucial to the evolution of the nascent neutron star. An important question of supernova physics is whether neutrino oscillations can occur deep enough in the supernova envelope to have a significant impact on the nucleosynthesis and even the shock revival of the supernova. It was pointed out recently that neutrino oscillations can occur on very short distance/time scales and even in the limit of (almost) zero neutrino masses. I will discuss the mechanism of this fast neutrino oscillation phenomenon and how one may understand it with a few simple but insightful toy models.

Faculty Host: Yong-Zhong Qian

Tuesday, December 12th 2017
11:15 am:
Speaker: Tomoya Nakatani
Subject: Recent advances in CPP-GMR materials: Heusler alloys and new non-magnetic spacers
Faculty Host: Paul Crowell
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.
2:00 pm:
Thesis Defense in PAN 110
Speaker: Ziran Wang, University of Minnesota
Subject: Magnetism for Data Storage: Magnetoresistance Enhancement by Wave Vector Filtering and Transition Shifts in HAMR
This is the public portion of Mr. Wang's thesis defense. His advisor is Randall Victora.

Magnetoresistive heterostructures have important applications in magnetic storage technology and spintronics. This thesis uses Green’s function techniques to calculate the transport properties of a novel structure Fe/Ag/Fe/InAs/Ag. We show that the magnetoresistance can be enhanced to above 1000% due to the wave-vector filtering effect imposed by the InAs layer; meanwhile, the resistance-area product is as low as ~10Ωµm^2. The magnetoresistance shows oscillations with the InAs thickness when the Fermi level is in the conduction band, and the oscillations are quantitatively explained by theory.
Heat-assisted magnetic recording (HAMR) is a leading technology for the next-generation magnetic data storage. This thesis uses micromagnetic simulations to study magnetization transition shifts induced by nonequilibrium spin dynamics in HAMR. We examine the effects of thermal profile, head velocity, damping, and head field rise-time. We also propose methods to determine spin temperature and its lag relative to lattice temperature. By quantifying switching time, spin temperature lag, and superparamagnetic writing, we show that superparamagnetic effects cause largest transition shifts and dominate in typical HAMR processes.

Wednesday, December 13th 2017
09:05 am:

Aaron Durgin & Chase McCabe, "Moessbauer Spectroscopy of Fe57 Compounds"

Jarod White, "NMR Spectroscopy"

Pedro Angulo-Umana & Kai Wang, "Optical Whispering Gallery Mode Resonances"

Jacob Christy & Mitchell Frand, "Single Photon Quantum Interference"

1:25 pm:
Speaker: Wolfram Brenig, Technical University Braunschweig
Subject: Thermal transport in Kitaev-Heisenberg spin systems

Mott insulators with strong spin orbit coupling have become a testbed for exotic quantum phases, spin liquids and emergent Majorana matter. In this context we present results for the thermal conductivity of the Kitaev-Heisenberg model on ladders and the Kitaev model on honeycomb lattices. In the pure Kitaev limit, and in contrast to other integrable spin systems, the ladder represents a perfect heat insulator. This is shown to be a direct fingerprint of fractionalization into mobile Majorana matter and a static Z2 gauge field. We find a full suppression of the Drude weight and a pseudogap in the conductivity. With Heisenberg exchange, we find a crossover from a heat insulator to conductor, due to recombination of fractionalized spins into triplons. Increasing the dimension, and for the 2D honeycomb lattice, we show that very similar behavior occurs with however dissipative heat transport resulting in the thermodynamic limit. Our findings rest on several approaches comprising a mean-field theory, complete summation over all gauge sectors, exact diagonalization, and quantum typicality calculations.

Faculty Host: Natalia Perkins
There is no seminar this week.

Thursday, December 14th 2017
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
11:30 am:
Thesis Defense in 301-20 Tate
Speaker: Ryan Arneson
This is the public portion of Mr. Arneson's thesis defense. His advisor is Robert Gehrz.

This is the public portion of Mr. Arneson's thesis defense. His advisor is Robert Gehrz.

3:35 pm:
There will be no colloquium this week.

Friday, December 15th 2017
10:00 am:
Thesis Defense in 301-20 Tate
Speaker: Karlen Shahinyan
Subject: Much Ado About Blazars: Investigations of Extreme Variability Patterns in the Very High Energy Gamma-ray Blazar Emission
This is the public portion of Mr. Shahinyan's thesis defense. His advisor is Lucy Fortson.
Speaker: No colloquium this week.
3:35 pm:
There will be no Colloquiium this week.
4:00 pm:
Thesis Defense in 110 PAN
Speaker: Sean Kalafut, University of Minnesota
Subject: Search for a WR boson and heavy neutrinos using the LHC and the CMS experiment
This is the public portion of Mr. Kalafut's Thesis Defense. His advisor is Roger Rusack.
4:40 pm:
To be announced.

Monday, December 18th 2017
12:00 pm:
Thesis Defense in 301-20 Tate
Speaker: Melanie Beck
Subject: Integrating human and machine intelligence in galaxy morphology classification tasks
This is the public portion of Ms. Beck's thesis defense. Her advisor is Claudia Scarlata.
12:15 pm:
There will be no seminar this week.

Tuesday, December 19th 2017
11:00 am:
Thesis Defense in 110 PAN
Speaker: Gordon Stecklein, University of Minnesota
Subject: Generation and Absorption of Pure Spin Currents Using Graphene Nonlocal Spin Valves
This is the public portion of Mr. Stecklein's thesis defense. His advisor is Paul Crowell.

In this talk I will discuss the fabrication and measurement of nanoscale devices in which a spin-polarized electrical current is used to inject spins into graphene, which then diffuse. We demonstrate the electrical detection of spins in graphene devices with micron-scale spin diffusion lengths and analyze how the spin lifetime and spin diffusion lengths are affected by electrostatic gating. The spin current absorbed by an adjacent ferromagnet is calculated and demonstrated to increase as the electrical conductance of the graphene/ferromagnet interface is improved. Quantitative modeling, including a finite element model of the spatial distribution of spins and the effect of a thin metallic island, indicates that the absorbed spin current is nearing the regime necessary for future technological applications.

1:00 pm:
Thesis Defense in Tate 201-20
Speaker: Mark Mackey, University of Minnesota
Subject: End-Effects in Diblock Copolymer Melts
This is the the public portion of Mr. Mackey's MS Thesis defense. His advisor is David Morse.
3:30 pm:
Speaker: Gino Graziano, University of Minnesota
Subject: Experimental signatures of Majoranas

Thursday, December 21st 2017
08:00 am:
Untitled in Physics

Friday, December 22nd 2017
Speaker: No colloquium this week.

Monday, December 25th 2017
08:00 am:

Tuesday, December 26th 2017
08:00 am:

Wednesday, December 27th 2017
4:30 pm:
CM Journal Club in PAN 120
The seminar is done for the semester.

Thursday, December 28th 2017
10:10 am:
Biophysics Seminar in 120 PAN
The seminar is done for the semester.
3:35 pm:
There will be no colloquium this week.

Friday, December 29th 2017
Speaker: No colloquium this week.
3:35 pm:
The seminar is done for the semester.
4:40 pm:
The seminar is done for the semester.

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