Physics and Astronomy Calendar

semester, 2019


Tuesday, January 1st 2019

Monday, January 14th 2019
10:00 am:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.
12:30 pm:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.

Tuesday, January 15th 2019
10:00 am:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.
1:00 pm:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.

Wednesday, January 16th 2019
10:00 am:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.
12:30 pm:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.

Thursday, January 17th 2019
08:00 am:
Untitled in Physics
08:00 am:
Untitled in Physics
10:00 am:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.
1:00 pm:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.

Friday, January 18th 2019
10:00 am:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.
12:30 pm:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.

Saturday, January 19th 2019
11:00 am:
This Physics Force show is open to the public. Tickets are $3 (see abstract below)

Tickets are $3, children under 10 are free.

Purchase tickets at Northrop box office.
Phone: 612-624-2345

4:00 pm:
This Physics Force show is open to the public. Tickets are $3 (see abstract below)

Tickets are $3, children under 10 are free.

Purchase tickets at Northrop box office.
Phone: 612-624-2345


Monday, January 21st 2019

Tuesday, January 22nd 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
Organizational Meeting

Wednesday, January 23rd 2019
1:30 pm:
There will be no seminar this week.
There will be no seminar this week.

Thursday, January 24th 2019
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
Speaker: Stephen Taylor, California Institute of Technology
Subject: Frontiers Of Multi-Messenger Gravitational-Wave Astrophysics
Today's Journal Club meeting will be the faculty candidate presentation

The bounty of gravitational-wave observations from LIGO and Virgo has opened up a new window onto the warped Universe, as well as a pathway to addressing many of the contemporary challenges of fundamental physics. I will discuss how catalogs of stellar-mass compact object mergers can probe the unknown physical processes of binary stellar evolution, and how these systems can be harnessed as standard distance markers (calibrated entirely by fundamental physics) to map the expansion history of the cosmos. The next gravitational-wave frontier will be opened within 3-6 years by pulsar-timing arrays, which have unique access to black-holes at the billion to ten-billion solar mass scale. The accretionary dynamics of supermassive black-hole binaries should yield several tell-tale signatures observable in upcoming synoptic time-domain surveys (like the Large Synoptic Survey Telescope), as well as gravitational-wave signatures measurable by pulsar timing. Additionally, pulsar-timing arrays are currently placing compelling constraints on modified gravity theories, cosmic strings, and ultralight scalar-field dark matter. I will review my work on these challenges, as well as in the exciting broader arena of gravitational-wave astrophysics, and describe my vision for the next decade of discovery.

3:35 pm:
Speaker: Roger Steuwer, U of Minnesota
Subject: From the Old to the New World of Nuclear Physics, 1919-1939
Refreshments in atrium after the Colloquium.

These two interwar decades, as I discuss in my new book, The Age of Innocence: Nuclear Physics between the First and Second World Wars (Oxford University Press. 2018), saw the nascent field of nuclear become the dominant field of experimental and theoretical physics owing to an international cast of gifted physicists. Prominent among them were Ernest Rutherford and James Chadwick, George Gamow, the husband and wife team of Frédéric and Irène Joliot-Curie, John Cockcroft and Ernest Walton, Ernest Lawrence, Enrico Fermi, Niels Bohr, Gregory Breit and Eugene Wigner, and Lise Meitner and Otto Robert Frisch. Their fundamental discoveries and pioneering inventions arose from a quest to understand nuclear phenomena; none were motivated by a desire to find a practical application for nuclear energy. In this sense, they lived in an “Age of Innocence.” They did not, however, live in isolation. Their research reflected their idiosyncratic personalities; it was shaped by the physical and intellectual environments of the countries and institutions in which they worked; and it was buffeted by the turbulent political events after the Great War--the harsh postwar treaties, the runaway inflation in Germany and Austria, and the intellectual migration from Germany and later from Austria and Italy.

Faculty Host: Michel Janssen

Friday, January 25th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
Organizational Meeting
12:20 pm:
Please note: The seminar that was announced in the previous calendar is cancelled, this week only.
12:30 pm:
There is no seminar this week
1:15 pm:
Thesis Defense in PAN 110
Speaker: Mahendra DC, University of Minnesota
Subject: High charge-to-spin and spin-to-charge conversion enhanced by quantum confinement effect in sputtered topological insulator thin films"
This is the public portion of Mr. DC's thesis defense. His advisor is Jian-Ping Wang.

The spin-orbit torque (SOT) arising from materials with large spin-orbit coupling promises a path for ultra-low power and ultra-high speed magnetic-based storage and computational devices. The SOT switching of magnetization can be used in SOT-memory and whereas the spin-to-charge conversion can be utilized for reading of magnetization state in spin-based logic device. Recent reports on topological insulators grown by MBE process show a relatively high SOT. However, this process is incompatible to modern semiconductor fabrication processes. An “unexpected” giant SOT effect was discovered in sputtered topological insulator through this research. This discovery led to and could be explained by our newly proposed concept: quantum-confinement in topological insulators. From the atomic force and transmission electron microscopy the magnetron-sputtered bismuth selenide thin films show unique nano-sized grains which are correlated with the thickness of the films. A systematic study on SOT effect in BixSe(1-x)/Co20Fe60B20 heterostructures was performed. Remarkably, the spin torque efficiency ( ) was determined to be as large as 18.62 ± 0.13 and 8.67 ± 1.08, using the dc planar Hall and spin-torque ferromagnetic resonance methods, respectively. Quantum transport simulations using a realistic sp3 tight binding model confirms that the giant SOT in sputtered BixSe(1-x) is due to the quantum confinement effect, whose charge-to-spin conversion efficiency enhances with reduced size and dimensionality. In addition to charge-to-spin conversion, I will also present results of spin-to-charge conversion in these sputtered bismuth selenide thin films. For the spin-pumping experiment, a conducting ferromagnet (CoFeB) and insulating ferrimagnet (YIG) were used to pump spins into the bismuth selenide layer. The spin-to-charge conversion voltage is affected by thermal effects such as the Nernst effect, anomalous Nernst effect, and spin Seebeck effect. The thermal contribution in the spin-to-charge conversion voltage was studied by using an insulating barrier. An additional spin-momentum locking was created by inserting a thin Ag layer in between bismuth selenide and CoFeB, which enhanced the spin-to-charge conversion figure of merit quite significantly.

There will be no colloquium this week. (Faculty candidate presentation on Thursday).
Speaker: Lucy Fortson, School of Physics and Astronomy, University of Minnesota
Subject: Optimizing the Human-Machine Partnership with Zooniverse
Note change of Colloquium time, this week only. Refreshments at 3:45 p.m.

Citizen science—the involvement of hundreds of thousands of people in the research process— provides a radical solution to the challenge of dealing with the greatly increased size of modern data sets. Zooniverse.org is the
most successful collection of online citizen science projects which have enabled over 1.7 million online volunteers to contribute to over 120 research projects spanning disciplines from astronomy to zoology. Dr. Lucy Fortson, cofounder of the Zooniverse and Associate Head and Professor in the School of Physics and Astronomy at the University of Minnesota will briefly describe the Zooniverse platform and some of the results to date from the
Zooniverse collection of online projects in the context of new approaches to combining machine learning with human classifications. She will then provide an overview of recent data science experiments with the ultimate goal of
producing a system that most efficiently balances the human and machine classifications. She will finish with a short description of future developments of the Zooniverse platform.

4:40 pm:
Speaker: Jochen Mueller, Biophysics

Monday, January 28th 2019
12:20 pm:
Speaker: TBD

Tuesday, January 29th 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.
Speaker: Andrew Zolli, Vice President, Global Impact Initiatives, Planet
Subject: Using Space to Help Life on Earth: How the Small Satellite Revolution and AI are Transforming How We See and Understand Our World

A revolution in low-cost, space-based remote sensing, combined with new analytical tools in machine learning, computer vision and artificial intelligence, are creating unprecedented new opportunities for tackling the world’s toughest challenges.

Andrew Zolli is the Vice President for Global Impact Initiatives at Planet (www.planet.com). Started by three NASA engineers, Planet has deployed the largest constellation of Earth-observation satellite in history. Together, these satellites image the entire surface of the Planet, every day, in high resolution. The resulting data holds transformational potential for basic science, and for a host of global challenges, including monitoring deforestation, agriculture and cities, tracking migration, mitigating the effects of climate change, speeding disaster response, and delivering planetary health, among others.

In this talk, Andrew will share lessons from the forefront of the New Space renaissance, as well as breakthrough new remote sensing applications being used right now around the world, and describe how new agile manufacturing and development technologies are accelerating the pace of innovation.


Wednesday, January 30th 2019
The seminar has been cancelled.
Faculty Host: Martin Greven
The seminar has been postponed until Friday afternoon.

Thursday, January 31st 2019
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
12:10 pm:
Speaker: Nico Adams and Terry Jones
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Boris Shklovskii, University of Minnesota
Subject: Coulomb gap here, there, and everywhere

In 1975 Alexei Efros and myself discovered that due to electron-electron interactions the density of localized electron states vanishes near the Fermi level as quadratic function of the energy distance to the Fermi level. We named this phenomenon the Coulomb gap and showed that it leads to the variable range hopping conductivity which depends on temperature T as \exp[-(T_ES/T)^1/2]. This ES law was observed in hundreds of experimental papers, where in many cases it describes 10^6 times variation of conductivity. After reminding the history and physics of this discovery I will review many new applications of ES law beyond lightly doped semiconductors, among which the Quantum Hall Effect is the most prominent. I will also dwell on McMillan-Shklovskii conjecture on the Coulomb gap evolution across an Insulator-Metal transition and related question of screening of the Coulomb gap.


Friday, February 1st 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
12:20 pm:
CM Sack Lunch in Tate 301-20
Speaker: Zedong Yang
Subject: Electronic transport in ballistic InSb nanowires with ferromagnetic contacts
12:30 pm:
Speaker: Asher Berlin (SLAC)
Subject: Thermal Relics Below an MeV

I will discuss a class of models in which thermal dark matter is lighter than an MeV. If dark matter thermalizes with the Standard Model below the temperature of neutrino-photon decoupling, constraints from measurements of the effective number of neutrino species are alleviated. This framework motivates new experiments in the direct search for sub-MeV thermal dark matter and light force carriers.

Speaker: Christopher Palmer (Princeton University)
Subject: Observation of the Higgs boson decaying to bottom quarks at CMS
Note change of time and day for this seminar, this week only.

The Higgs boson decay to a bottom quark-antiquark pair has been sought
for decades by the high energy community (i.e. at LEP and Tevatron).
LHC experiments built analyses based on the experience of Tevatron
experiments' analysis techniques. With the observation of the Higgs
boson at LHC during Run 1, the search for this decay channel became
sharply focused. As the bottom quark pair channel is the most
probable decay of the Higgs boson (58%), its observation is both
important in terms of quantifying the Higgs boson and it represents an
important milestone in high energy physics. The results presented use
datasets from the LHC Run 1 and Run 2 (2016+2017) from CMS. This Run
2, 13 TeV dataset corresponds to an integrated luminosity of ~80
fb^-1. The analysis strategy, the background estimation techniques,
and significant analysis improvements from the 2017 data analysis in
CMS are shown. An outlook on the upcoming analysis of the full Run 2
dataset (and beyond) will be discussed.

There will be no colloquium this week
Speaker: Stephen Snobelen, Humanitites, King's College, Halifax
Subject: Science, religion and the New Atheism: the view from the history and philosophy of science
Refreshments served at 3:15 p.m.
4:40 pm:
Speaker: Vincent Noireaux, Biophysics

Monday, February 4th 2019
12:15 pm:
Speaker: Eliu Huerta
Subject: Convergence of gravitational wave astrophysics, large scale astronomical surveys and data science: A gateway for discovery in the Multi-Messenger Astrophysics Era
MifA faculty candidate

The next decade promises fundamental new scientific insights and discoveries from Multi-Messenger Astrophysics, enabled through the convergence of large scale astronomical surveys, gravitational wave astrophysics, deep learning and large scale computing. In this talk I describe a Multi-Messenger Astrophysics science program, and highlight recent accomplishments at the interface of gravitational wave astrophysics, numerical relativity and deep learning. I discuss the convergence of this program with large scale astronomical surveys in the context of gravitational wave cosmology. Future research and development activities are discussed, including a vision to leverage data science initiatives at the University of Minnesota through transdisciplinary research to spearhead, maximize and accelerate discovery in the nascent field of Multi-Messenger Astrophysics.


Tuesday, February 5th 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
To be announced

Wednesday, February 6th 2019
1:25 pm:
Speaker: Rafael Fernandes, University of Minnesota
Subject: Vestigial orders in electronic correlated systems: nematicity and beyond

A hallmark of the phase diagrams of correlated electronic systems is the existence of multiple electronic ordered states. In many cases, they cannot be simply described as independent competing phases, but instead display a complex intertwinement. A prime example of intertwined states is the case of primary and vestigial phases. While the former is characterized by a multi-component order parameter, the fluctuation-driven vestigial state is characterized by a composite order parameter formed by higher-order, symmetry-breaking combinations of the primary order parameter. This concept has been widely employed to elucidate nematicity in both iron-based and cuprate superconductors. In this talk, I will present a group-theoretical framework, supplemented by microscopic calculations, that extends this notion to a variety of phases, providing a general classification of vestigial orders of unconventional superconductors and density-waves. Electronic states with scalar and vector chiral order, spin-nematic order, Ising-nematic order, time-reversal symmetry-breaking order, and algebraic vestigial order emerge from this simple underlying principle. I will present a rich variety of possible phase diagrams involving the primary and vestigial orders, and discuss possible realizations of these exotic composite orders in different materials.

1:25 pm:
Speaker: Richard Anthony D'Souza, University of Michigan
Subject: Unravelling the Andromeda Galaxy's most important merger

The Andromeda Galaxy (M31), our nearest large galactic neighbour, offers a unique opportunity to test how mergers affect galaxy properties. M31's stellar halo caused by the tidal disruption of satellite galaxies is the best tracer of the galaxy's accretion history. Despite a decade of effort in mapping out M31's large stellar halo, we are unable to convert M31's stellar halo into a merger history. Here we use cosmological models of galaxy formation to show that M31's massive and metal-rich stellar halo containing intermediate age stars implies that it merged with a large (M* ~ 2.5 x 10^10 M_sun) galaxy ~2 Gyr ago. The simulated properties of the merger debris help to interpret a broader set of observations of M31's stellar halo and satellites than previously considered: its compact and metal-rich satellite M32 is the tidally-stripped core of the disrupted galaxy, M31's rotating and flattened inner stellar halo contains most of the merger debris, and the giant stellar stream is likely to have been thrown out during the merger. This accreted galaxy was the third largest member of the Local Group. This merger may explain the global burst of star formation ~2 Gyr ago in the disk of M31 in which ~1/5 of its stars were formed. Moreover, M31's disk and bulge were already in place before its most important merger, suggesting that mergers of this magnitude do not dramatically affect galaxy structure.

Faculty Host: Evan Skillman
Speaker: Andrew Furmanski (The University of Manchester)
Subject: Neutrinos at Short Baselines

Neutrino oscillations are being measured carefully across a broad range
of experiments, but there remain some anomalies that have not been fully
explained. Using three liquid argon TPCs on the same neutrino beam, the
short baseline neutrino program at Fermilab will set the worlds best
limits on eV-scale sterile neutrinos, whilst developing liquid argon
technology critical for DUNE and making precision measurements of
neutrino-argon interactions. MicroBooNE - the first operating TPC in
the SBN program - has been collecting data since late 2015. This talk
will describe the current status of the three-detector experiment, and
present the first physics results with MicroBooNE data.


Thursday, February 7th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker:  Karunya Kandimalla, Associate Professor at Department of Pharmaceutics of the University of Minnesota
Subject: Nanovehicles for the Diagnosis and Treatment of Blood-Brain Barrier Dysfunction in Neurodegenerative Diseases

The blood brain barrier (BBB) performs dual functions of restricting the entry of xenobiotics into brain while serving as the major signaling and material trafficking portal between plasma and brain. Moreover, the BBB modulates cerebral blood flow to sustain neuronal activity; handles glucose as well as insulin delivery to brain; and maintains immune and inflammatory communication between periphery and brain. These critical BBB functions are disrupted in neurodegenerative disease like Alzheimer’s disease and cerebral amyloid angiopathy. We developed therapeutic nanoparticles to detect and treat BBB dysfunction in these diseases.
For successful brain delivery, a nanoparticle must withstand dominant clearance pressure from the peripheral reticuloendothelial system, marginate from the bulk blood flow to the vascular endothelium, permeate the blood-brain-barrier, and accumulate at the target site. In addition to these common challenges, the nanoparticles intended for cerebrovascular targeting must incorporate appropriate design elements to ensure their retention in the cerebral vasculature. Furthermore, a functionally optimized nanoparticle design demands synergistic amalgamation of the physicochemical properties of various components and their intended physiological effects. Strategies developed in our laboratory to surmount these barriers will be discussed in the talk.

Speaker: Michael Coughlin, California Institute of Technology
Subject: Searching for compact binaries in the gravitational-wave and optical time domain
Today's Journal Club meeting will be the faculty candidate presentation

Binary neutron star mergers provide one of the richest laboratories for studying physics with ground-based interferometric gravitational-wave detectors such as advanced LIGO and Virgo. After such a merger, a compact remnant is left over whose nature depends primarily on the masses of the inspiralling objects and on the equation of state of nuclear matter. We will discuss the search for post-merger signals from GW170817. In addition, we will describe ongoing searches for the detection of transients like GW170817 in electromagnetic wavelengths. With the Zwicky Transient Facility (ZTF) recently achieving first light, it is now fruitful to use its unprecedented combination of depth, field of view, and survey cadenceto perform Target of Opportunity observations. We willdemonstrate on short gamma-ray bursts how it is possible to use this system to do follow-up on this scale. Finally, we will discuss the ongoing efforts to use ZTF and a new instrument at the Kitt Peak 2.1m to find and characterize white dwarf binaries.

3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Marcelo Magnasco, The Rockefeller University
Subject: Shifting attention to dynamics: Self-reconfiguration of neural networks

In recent years, considerable evidence has accrued indicating that brain function can be flexibly reconfigured on the fly: certain brain areas are capable of carrying out a variety of different functions and are able to switch between those functions in a context-sensitive, dynamic fashion. Some evidence has also emerged that ongoing brain activity, the ceaseless background brain dynamics, may be implicated in setting and controlling these dynamic functions as well as attentional gain control. A crucial link between them is dynamics. I will discuss both the accumulating evidence as well as a theoretical outline of dynamical mechanisms for functional self-reconfiguration of neural networks, including reconfiguration of logic function, reconfiguration of information routing, and poising at critical points to reconfigure dynamics.

Faculty Host: Jorge Vinals

Friday, February 8th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
12:20 pm:
Speaker: Hsiu-Chung Yeh
Subject: Emptiness formation probability in Lieb-Liniger model.
12:30 pm:
Speaker: Eric Braaten (Ohio State U.)
Subject: Axion Stars

The particle that makes up the dark matter of the universe could be an axion. A significant fraction of the axion dark matter could be in the form of bound Bose-Einstein condensates of axions. The condensates are called "axion stars" if they are bound by gravity and "oscillons" if they are self-bound. There may be aspects of axion dark matter in which the effects of axion stars and oscillons have not been fully taken into account.

There will be no colloquium this week. (Faculty candidate presentation on Thursday).
Speaker: Stephen Snobelen, History of Science and Technology - King's College, Halifax
Subject: Science, Religion and the New Atheism: the view from the history and philosophy of science
Refreshments served at 3:15 p.m.
3:35 pm:
Speaker: Miranda Pihlaja Straub, University of Minnesota
Subject: To be announced.
The seminar has been cancelled.
4:40 pm:
Speaker: Shaul Hanany, Cosmology

Monday, February 11th 2019
12:15 pm:
Speaker: Jennifer Barnes, Columbia University
Subject: Panning for gold with things that go bang in the night
MifA faculty candidate

Electromagnetic follow-up observations of the gravitational wave-detected binary neutron star merger (NSM) GW1701817 suggested that material ejected from the accretion disk formed in the merger underwent a robust r-process nucleosynthesis, producing heavy elements like Au, Pt, and Eu. These observations seemed to answer a long-standing question about the origin of the heaviest elements in the Universe. However, the conditions that characterize the disks formed in NSMs are also found in other systems, raising the question of whether mergers are unique sites of r-process production. Of particular interest for this question is the collapse of rapidly-rotating massive stars, called "collapsars." Like NSMs, collapsars form accretion disks around stellar mass compact objects and are associated with ultrarelativistic outflows that give rise to gamma-ray bursts, similarities that suggest they may also host an r-process. I will review the theoretical progress that allowed the identification of the emission accompanying GW170817 as a specifically r-process-powered transient. I will then discuss recent work that explores whether collapsar disks could successfully produce the r-process, and what the signs of collapsar disk r-process nucleosynthesis might be. I will conclude by highlighting upcoming advances that will allow us to make progress on understanding of r-process origins and other mysteries of the multi-messenger era.


Tuesday, February 12th 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Peter Bruggeman, Mechanical Engineering, UMN
Subject: Physics of Low Temperature Plasmas: a Unique Non-Equilibrium State for Tackling Grand Societal Challenges
Speaker: Shai Ashkenazi and Taner Akkin, Associate Professors of Biomedical Engineering, University of Minnesota
Subject:  Photoacoustic Imaging (Ashkenazi) and Polarized Light Imaging (Akkin) for Biomedical Applications

The field of Photoacoustic Imaging (PAI) for medical and biological applications has changed dramatically in the past two decades. It has evolved from a bulk absorption spectroscopy technique for sample analysis into a high resolution imaging modality. It is a change similar to the evolution of Magnetic Resonance Spectroscopy (MRS) into Magnetic Resonance Imaging (MRI). However, as opposed to the rapid adoption of MRI in medical diagnosis, PAI is still not in use in clinics. The reasons may be insufficient depth penetration, cost (relative to alternatives), bulky laser systems, and challenging engineering design of light and ultrasound delivery. Yet, the attraction of PAI is its ability to embed optical tissue properties in a plain ultrasound image. This way extending ultrasound imaging to functional and molecular imaging modality. Dr. Ashkenazi will introduce the basic principles of PAI and then move to explore different mechanisms of contrast that can be implemented in PAI. Primarily, he will focus on using transient absorption and triplet-triplet absorption as a potential contrast for PAI in medical applications.
PART-II: Polarization is an essential but underutilized property of light. Imaging systems that are capable of making polarization-sensitive measurements require careful design and in some cases use of sophisticated analysis methods. Dr. Akkin will present optical coherence tomography (OCT) based depth-resolved tissue imaging for which the intensity, phase and polarization properties of backscattered/reflected light are analyzed to extract various imaging contrasts. This label-free imaging and mapping technique will be introduced for generating 3D optical tractography of whole-brain microconnectivity with serial sectioning. Also, he will present contrast enhancement by titanium dioxide perfusion, which enables visualization of the vasculature in cross-polarization images. Signal and image processing approaches as well as deep learning algorithms are being developed for better visualization and separation of the vascular and white matter networks.

4:40 pm:
CM Journal Club in Tate 201
Subject: Exact Diagonalization

Wednesday, February 13th 2019
1:25 pm:
Speaker: Andrey Chubukov, University of Minnesota, TPI
Subject: TBD
Speaker: Yangyang Cheng (Cornell University)
Subject: A New Paradigm for Dark Matter Search at the LHC

The existence of dark matter (DM), through astrophysical and cosmological observations, presents some of the most striking evidence of physics beyond the Standard Model. Stringent limits have been placed on DM as a Weakly Interacting Massive Particle (WIMP) from direct and indirection detection as well as collider experiments. If instead of one type of DM particle, nature contains a complex dark sector, the new hidden particles can evade existing DM limits and most direct detection experiments, but may be produced at high-energy colliders like the LHC. Many dark sector models predict long-lived particles with striking collider signature, opening an exciting new paradigm for dark matter
search. This talk overviews the landscape for dark matter search, and
introduces the physics motivation for a complex dark sector with long-lived particles. It then describes two types of signature-driven dark sector searches at the CMS experiment, for a dark shower and for displaced lepton jets. Finally, the talk discusses prospects for dark sector searches at the High-Luminosity LHC with detector and trigger upgrades, in particular how the new forward detectors and enhanced timing capabilities can reach new phase spaces and sensitivities.


Thursday, February 14th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Jiali Gao, Department of Chemistry, University of Minnesota
Subject: Allosteric Regulation of Biological Function of Photoreceptor proteins

Major light-harvesting complex of photosystem II (LHCII) is a photoreceptor protein that regulates energy transfer and dissipation in response to rapid fluctuations of light intensity, directly affecting the efficiency of photosynthesis. In this presentation, I will describe an investigation combining molecular dynamics simulation and temperature-jump time-resolved IR spectroscopy to understand the mechanism of energy dissipation in LHCII. I will illustrate an allosteric regulation of the global protein conformational changes induced by a local conformational transition of random coils into α-helices due to changes of external temperature and acidity. The dynamic motions induce close contacts between the associated luteins (Lut) and photoactivated chlorophyll (Chl) chromophores to facilitate fluorescence quenching. In addition, I will discuss a multistate density functional theory designed to model photochemical and charge transfer processes.

Speaker: Sarah Vigeland, University of Wisconsin-Milwaukee
Subject: Probing Massive and Supermassive Black Holes with Gravitational Waves
Today's Journal Club meeting will be the faculty candidate presentation

Observations have shown that nearly all galaxies harbor massive or supermassive black holes at their centers. Gravitational wave (GW) observations of these black holes will shed light on their growth and evolution, and the merger histories of galaxies. Massive and supermassive black holes are also ideal laboratories for studying strong-field gravity. Pulsar timing arrays (PTAs) are sensitive to GWs with frequencies ~1-100 nHz, and can detect GWs emitted by supermassive black hole binaries, which form when two galaxies merge. The Laser Interferometer Space Antenna (LISA)is a planned space-based GW detector that will be sensitive to GWs ~1-100 mHz, and it will see a variety of sources, including merging massive black hole binaries and extreme mass-ratio inspires (EMRIs), which consist of a small compact object falling into a massive black hole. I will discuss source modeling and detection techniques for LISA and PTAs, as well as present limits on nanohertz GWs from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration.

3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Reinhard Schwienhorst, Michigan State University
Subject: The Tevatron legacy and the LHC through the lens of single top-quark production

Single top-quark production has provided flagship top-quark measurements at the Tevatron and LHC. These electroweak production modes have small production cross-sections and final states with large backgrounds, challenging the understanding of the detector, while also demanding innovations in analysis techniques. Single top measurements constrain models of new physics directly and indirectly and provide a direct determination of the CKM matrix element Vtb. All this makes single top an excellent representation of the core Tevatron and LHC programs. I will review the history of single top-quark measurements and discuss their role in future LHC runs.

Faculty Host: Roger Rusack

Friday, February 15th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Aditya Dhumuntarao, University of Minnesota
Subject: Chaos in Action: Developing an Action Principle for Open Systems
12:20 pm:
Speaker: Bo Xiong
Subject: 1D ideal gas of anyons obeying Haldane exclustion statistics.
12:30 pm:
Speaker: Andrew Long (U. Michigan)
Subject: Ultra-light dark photons from a network of cosmic strings

A variety of experimental efforts are currently underway to detect ultra-light dark photon dark matter — a spin-1 particle dark matter candidate with mass below 1 eV. However, dark photon dark matter has a notorious production problem: it is challenging to write down a model that yields the correct relic abundance of non-relativistic dark photons. In this talk I will discuss how dark photon dark matter is created from a network of near-global, Abelian-Higgs cosmic strings. These strings are expected to survive in the universe today, and their motions create a stochastic gravitational wave noise.

There will be no colloquium this week. (Faculty candidate presentation on Thursday).
3:35 pm:
Speaker: Kaylee Ganser, University of Minnesota
Subject: Student Conceptual Understanding of Newtonian Physics Across Different Introductory Courses at UMN

Engineering based introductory physics differs from biology based introductory physics in the UMN Physics department in both content and class makeup. Performance on a concept inventory was tested across 23 classrooms with a total of 2290 students, and it was found that, after controlling for student gender, initial concept inventory score, and initial math proficiency, there was no difference in student performance on the post-test of the concept inventory between classes. A gender gap was found in the data- the performance of women was, on average, less than men on the post-test, though the gap varied significantly, suggesting that there is variation in how the gender gap manifests in different classrooms. This talk will go through the data collection, analysis methods, and implications of these results.

4:40 pm:
Speaker: Bharat Jalan, CEMS

Monday, February 18th 2019
12:15 pm:
Speaker: TBD
3:35 pm:
Speaker: David Caratelli (FNAL)
Subject: Neutrinos in High Definition

Thanks to advances in detector technology and the advent of powerful neutrino sources, neutrino physics in the past decade has rapidly moved to an era of precision measurements. With these new tools, we hope to shed light on their curious properties, and address fundamental questions on the fabric of our universe. In this seminar I will talk about how the MicroBooNE experiment is using a new detector technology to understand an anomaly in neutrino physics that has motivated many interesting phenomenological models. The talk will describe the MicroBooNE experiment, a short-baseline neutrino detector sitting in a ~1 GeV beam, and the status of the measurement of electron neutrino
interactions. I will focus on illustrating how the study of electromagnetic activity in LArTPC detectors enables MicroBooNE’s study of electron neutrino interactions as well as the broader neutrino oscillation physics program to be carried out at Femilab. Finally, I will describe how low-energy electromagnetic signatures can expand this detector technology’s physics reach to explore BSM physics and astrophysical signatures.


Tuesday, February 19th 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Cynthia Cattell and Chris Colpitts
Subject: Wave generation by relativistic electron beams in a plasma: Initial results fromLAPD run
There will be no seminar this week.

Wednesday, February 20th 2019
1:25 pm:
Speaker: Boris Spivak, University of Washington
Subject: Magneto-transport phenomena related to the chiral anomaly in Weyl and Dirac semimetals

I will present a theory of magnetotransport phenomena related to the chiral anomaly in Weyl semimetals. I will show that conductivity, thermal conductivity, thermoelectric and the sound absorption coefficients exhibit strong and anisotropic magnetic field dependences. I will also discuss properties of magneto-plasmons and magneto-polaritons, whose existence is entirely determined by the chiral anomaly.

Faculty Host: Boris Shklovskii
Speaker: Nadja Strobbe (FNAL)
Subject: Taking aim at New Physics

The Standard Model of Particle Physics has been immensely successful. However, many questions remain, such as the nature of dark matter, the origin of the matter-antimatter asymmetry, and the question of naturalness and the hierarchy problem. A variety of New Physics models have been proposed to address these questions. One class of such new physics models is supersymmetry (SUSY).

Many searches for SUSY have been performed with the LHC data, and so far, none has found any signs of physics beyond the Standard Model. A theme common to many of these searches is the reliance on the presence of substantial missing transverse momentum (MET) from undetected SUSY particles. It is therefore reasonable to wonder whether SUSY could take a form that instead produces low-MET final states, thereby evading detection in standard searches.

In this seminar I will first discuss the motivation and strategy behind some of the traditional SUSY searches, focusing in particular on searches for the top squark. Then, I will introduce SUSY models that lead to low-MET final states, including stealth SUSY and R-parity violating SUSY. I will describe a novel analysis that takes aim at the challenging final state with top quarks, many extra jets, and low MET. Finally, I will conclude with a look towards the future, including HL-LHC projections for SUSY searches.


Thursday, February 21st 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Gordon Smith, Assistant Professor, Department of Neuroscience, UMN
Subject: Development of large-scale networks in visual cortex.

Sensory perception requires the coordinated activity of tens of thousands of neurons, working together in large-scale networks. As developmental events define and constrain the ultimate capabilities of these networks, it is therefore essential to understand the mechanisms underlying their formation. This talk will present recent work showing that in the developing visual cortex, correlations in spontaneous neural activity define large-scale functional networks with precise local and long-range organization that span millimeters of cortical area. These early networks predict future stimulus-evoked activity well before it can be visually driven, suggesting they form a substrate for building a mature large-scale functional architecture.

12:10 pm:
Speaker: Grantland Hall and Pat Kelly
3:30 pm:
Special Public Lecture in Best Buy Theater, Northrop, University of Minnesota
Speaker: Roger Launius, Chief Historian for NASA and Senior Curator of the Smithsonian Air and Space Museum (retired)
Subject: Why Go to the Moon? Apollo, the Space Race, and the Many Faces of Lunar Exploration
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Flavio Cavanna, Yale
Subject: Lifting the lid on DUNE, the new international mega-science project in the US

The experimental discoveries of the last half century have placed neutrinos in the spotlight to unlock the mysteries of the matter's abundance unbalance in the Universe and of the ultimate fate of the stars. The lack of direct observations of proton decays, on the other hand, keeps at bay the dream that the forces of nature were unified at the beginning of time.
The Deep Underground Neutrino Experiment (DUNE) is the new leading-edge, international mega-science experiment for neutrino science and proton decay search.
DUNE will consist of two paired neutrino detectors placed in the world’s most intense neutrino beam. One massive detector will be installed deep underground at the SURF laboratory, in South Dakota — 1,300 kilometers away from FERMILAB, where the second detector will be positioned just downstream the neutrino source. Detecting the energetic beam neutrinos at the far site and comparing with those detected at the near site can give insight about our matter dominated universe. The underground location of the far detector, screened from the overwhelming cosmic ray flow, may allow to detect tiny signals from neutrinos originated by a core-collapse supernova in the Milky Way and thus possibly peer inside a newly-formed neutron star. And finally, the extra-large amount of mass of the detector may allow primordial symmetries to occasionally resurface inside a proton and spontaneously morphing a quark into a lepton, with the proton instantly falling apart into a detectable flash of radiation.
But not only large mass and far distance matter to pursue this ambitious discovery plan: unprecedented detection technologies and a worldwide effort to build the detector are required. DUNE will use the state-of-the-art Liquid Argon TPC technology to instrument deep underground 70.000 tons of Liquid Argon at 87K, with millimeter scale 3D precision.
A 1 kTon precursor of the far LAr-TPC detector has been constructed and recently activated at the CERN Neutrino Platform, and is now taking data. A first look of the spectacular events collected will be shown.

Faculty Host: Roger Rusack

Friday, February 22nd 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Tom Welle, University of Minnesota
Subject: To be announced.
12:20 pm:
Speaker: Xiaojun Fu
Subject: Broken symmetry states in the N = 3 Landau level of GaAs quantum wells with alloy disorder
12:30 pm:
High Energy Theory Lunchtime Seminar in Tate 110 (note location change for this week)
Speaker: Radu Roiban (Penn State)
Subject: Classical physics from quantum scattering amplitudes: high orders in the post-Minkowskian approximation for binary systems
2:30 pm:
Speaker: Anna Williams, Macalester University
Subject: Exploring the coevolution of magnetic fields and galaxies in different environments

Galaxies are permeated with magnetic fields at all scale lengths--from protostellar disks to spiral arms. But how galaxies first acquired magnetic fields, and, in turn grow and sustain large-scale magnetic structures is not well understood. One way to unravel this problem is by observing magnetic fields in a variety of galaxy environments. Luckily, new and upgraded radio telescopes are providing a new window to the polarization universe, and greatly enhancing our ability to probe astrophysical magnetic fields. I will present the results of three observational studies focused on the coevolution of magnetic fields and galaxies in different environments: (1) a nearby spiral galaxy, NGC 6946, (2) a loose galaxy group, NGC 2563, and (3) distant disk-like galaxies at z~0.5.

Speaker: Michael Gordin, History - Princeton University
Subject: Einstein in Bohemia: Science and Prague before and after the Habsburgs
Refreshments served at 3:15 p.m.
3:35 pm:
There will be no seminar this week.
Speaker:  Carolyn Bishoff, UMN Libraries

Monday, February 25th 2019
12:15 pm:
Speaker: TBD
2:20 pm:
Speaker: Dr. Christina Ignarra (SLAC)
Subject: Expanding the Science Reach of Dark Matter Detection with the LZ Experiment

LUX-ZEPLIN (LZ) is a 10 tonne liquid xenon Time Projection Chamber (TPC) which will search for Weakly Interacting Massive Particle (WIMP) dark matter via direct scattering from xenon nuclei. This talk will give an overview of the LZ experiment and describe searches for nonstandard interactions governed by Effective Field Theory (EFT). The resulting nuclear responses from such interactions can lead to higher energy recoil spectra and signatures compared with conventional signals. I will also discuss technical innovations in areas such as high voltage, purification, and calibrations, which will allow us to improve sensitivity in both the high and low energy regimes.


Tuesday, February 26th 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Y. Miyoshi (Nagoya University, Project Scientist of ERG/Arase mission) and Y. Kasahara (Kanazawa University)
Subject: 1. Overview of Arase and highlights from the prime mission. 2. Highlights from plasma wave observation by Arase

These are two talks on the Japanese radiation belt mission, ARASE.

Speaker: Derryl Wright
Subject: Machine Learning and Citizen Science at Zooniverse

As researchers gather ever larger data sets there is an increasing reliance on machine learning and demand for citizen science. We will introduce Zooniverse, the world's largest citizen science platform and show how citizen science is helping researchers unlock meaningful information from the data they collect. We will also demonstrate how, classifications produced by volunteers, are enabling machine learning and that both citizen science and machine learning can empower each other to process data more efficiently than either alone.

Faculty Host: Vuk Mandic

Wednesday, February 27th 2019
1:25 pm:
Speaker: Joerg Schmalian, Karlsruhe Institute of Technology
Subject: Hierarchy of Information Scrambling, Thermalization, and Hydrodynamic Flow in Graphene

We determine the information scrambling rate due to electron-electron Coulomb interaction in graphene. The scrambling rate characterizes the growth of chaos and has been argued to give information about the thermalization and hydrodynamic transport coefficients of a many-body system. We discuss the scrambling rate at strong coupling, using a direct diagrammatic analysis and holographic methods and show that scrambling behaves similar to transport and energy relaxation rates. A weak coupling analysis, however, reveals that scrambling is in fact related to dephasing and single particle relaxation. Thus, while scrambling is obviously necessary for thermalization and quantum transport, it does generically not set the time scale for these processes.

Faculty Host: Rafael Fernandes

Thursday, February 28th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Paul Jardine, Associate Professor, Department of Diagnostic and Biological Sciences, UMN
Subject: Using Model Systems to Drive Methods Development – The Tale of a Viral RNA

Model systems serve a critical role in the development of new research methodologies. By their nature, model systems are well defined and therefore present excellent opportunities to extend the resolution, range of application, and rigour of advanced biochemical and biophysical experimental techniques. Given that they are, by definition, some of the simplest living systems, viral model systems have been used to advance all areas of molecular biology and biophysics. Here, I will summarise the experimental history of one small component of a viral force generator nanomotor – the prohead RNA (pRNA) component of the bacteriophage phi29 DNA packaging machine – and illustrate how the study of this molecule has revealed fundamental insight into biological macromolecules. The study of pRNA has contributed to the development of experimental approaches that can be adapted to more complex systems in order to address more complex questions in biological systems.

12:10 pm:
Speaker: Roberta Humphreys and Avery Garon
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Joerg Schmalian, Karlsruhe Institute of Technology
Subject: Failed Theories of Superconductivity

Superconductivity is one of the most fascinating quantum states of matter. Almost half a century passed between the discovery of superconductivity by Kamerlingh Onnes and the theoretical explanation of the phenomenon by Bardeen, Cooper and Schrieffer (BCS). During the intervening years the brightest minds in theoretical physics tried and failed to develop a microscopic understanding of the effect. A summary of some of those unsuccessful attempts to understand superconductivity not only demonstrates the extraordinary achievement made by formulating the BCS theory, but also illustrates that mistakes are a natural and healthy part of scientific discourse, and that inapplicable, even incorrect theories can turn out to be interesting and inspiring.

Faculty Host: Rafael Fernandes

Friday, March 1st 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
12:20 pm:
Speaker: Dan Shaffer, David Harrison, Brenda Knauber, Michael Sammon, Yilikal Ayino
Subject: March Meeting rehearsals
12:30 pm:
Speaker: Ken Van Tilburg (IAS/New York U.)
Subject: Halometry from Astrometry

Halometry---mapping out the spectrum, location, and kinematics of nonluminous structures inside the Galactic halo---can be realized via effects that variable weak gravitational lensing induces on the proper motions of stars and other luminous background sources. Modern astrometric surveys provide unprecedented positional precision along with a leap in the number of cataloged objects. Astrometry thus offers a new and sensitive probe of collapsed dark matter structures over a wide mass range, from one millionth to several million solar masses. It opens up a window into the spectrum of primordial density fluctuations with very small comoving wavenumbers, scales hitherto poorly constrained.
I will outline several detection strategies for dark matter substructure based on time-domain weak gravitational lensing, after summarizing existing techniques and constraints. I will present preliminary results from ongoing analyses based on Gaia's second data release. Finally, I will show that minimal models of axion-like dark matter naturally produce dense small-scale structures which can probed by the aforementioned astrometric lensing techniques.

2:30 pm:
Speaker:  Dale Gary, New Jersey Institute of Technology
Subject: A Breakthrough View of Solar Flares from Radio Imaging Spectroscopy

Solar flares are the result of explosive release of stored magnetic energy in the Sun's corona. The detailed physical processes that underlie the rapid conversion of such energy to other forms, particularly the acceleration of electrons and ions to relativistic energies, remain mysterious, partly because direct measurements of the coronal magnetic field and the spatial and energy distribution of the particles have been difficult or impossible. One emission mechanism that is sensitive to the coronal magnetic field in the flaring region is radio emission, but until recently the instrument capabilities needed to exploit that sensitivity have not been available. However, this has changed with the completion of a new, solar dedicated radio interferometer array, the Expanded Owens Valley Solar Array (EOVSA), that has the required combination of spatial, spectral, and temporal resolution to make these breakthrough measurements. In this talk, I illustrate the new capabilities and their implications using observations of a showcase solar flare that occurred on 2017 September 10. This event is a textbook example of the "standard solar flare model" eruptive event, with a clearly visible reconnecting current sheet connecting an erupting flux rope with a growing arcade of newly formed "post-flare" loops. The comparison of microwave diagnostics of high-energy electrons with those from hard X-rays seen by the RHESSI spacecraft show that, while they are fully consistent, the microwaves reveal that the coronal volume containing high-energy particles is much larger and more widespread than would have been deduced from hard X-rays alone. Even more important, however, are the quantitative measurements of the spatially and temporally resolved magnetic field strength, which, if our interpretation is correct, directly reveal the conversion of magnetic energy over a large volume into high-energy charged particles.and turbulent plasma. The new observations present both a challenge and an opportunity for further theoretical understanding of the processes occurring in solar flares.

Faculty Host: John Wygant
Speaker: Nükhet Varlık , History - Rutgers University
Subject: Five-Hundred Years of Plague in Ottoman History: Re-thinking the Second Pandemic
Refreshments served at 3:15 p.m.
3:35 pm:
Speaker: Kaylee Ganser, University of Minnesota
Subject: Student Conceptual Understanding of Newtonian Physics Across Different Introductory Courses at UMN

Engineering based introductory physics differs from biology based introductory physics in the UMN Physics department in both content and class makeup. Performance on a concept inventory was tested across 23 classrooms with a total of 2290 students, and it was found that, after controlling for student gender, initial concept inventory score, and initial math proficiency, there was no difference in student performance on the post-test of the concept inventory between classes. A gender gap was found in the data- the performance of women was, on average, less than men on the post-test, though the gap varied significantly, suggesting that there is variation in how the gender gap manifests in different classrooms. This talk will go through the data collection, analysis methods, and implications of these results.

Speaker: Lee Penn, CHEM and Diversity Committee

Monday, March 4th 2019
12:15 pm:
Speaker: TBD

Tuesday, March 5th 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Demoz Gebre Egziabher, Aerospace Engineering, UMN
Subject: Signal of Opportunity Navigation in Deep. Space
Speaker: Georgios Giannakis
Subject: Online Scalable Learning Adaptive to Unknown Dynamics and Graphs

Kernel based methods exhibit well-documented performance in various nonlinear learning tasks. Most of them rely on a preselected kernel, whose prudent choice presumes task-specific prior information. Especially when the latter is not available, multi-kernel learning has gained popularity thanks to its flexibility in choosing kernels from a prescribed kernel dictionary. Leveraging the random feature approximation, this talk will introduce first for static setups a scalable multi-kernel learning approach (termed Raker) to obtain the sought nonlinear learning function ‘on the fly,’ bypassing the `curse of dimensionality’ associated with kernel methods. We will also present an adaptive multi-kernel learning scheme (termed AdaRaker) that relies on weighted combinations of advices from hierarchical ensembles of experts to boost performance in dynamic environments. The weights account not only for each kernel’s contribution to the learning process, but also for the unknown dynamics. Performance is analyzed in terms of both static and dynamic regrets. AdaRaker is uniquely capable of tracking nonlinear learning functions in environments with unknown dynamics, with analytic performance guarantees. The approach is further tailored for online graph-adaptive learning with scalability and privacy. Tests with synthetic and real datasets will showcase the effectiveness of the novel algorithms.

Faculty Host: Vuk Mandic

Wednesday, March 6th 2019
1:25 pm:
March APS Meeting - No speaker this week
Speaker: Jim Linnemann, Michigan State University
Subject: HAWC: Extreme Astronomy with Big Buckets of Water

Though we can see thousands of stars in a clear night sky, the number of known sources emitting TeV gamma rays is less than 200. This is both because there are few instruments capable of measuring such photons, and because the sources are restricted to particularly violent astrophysical processes which
produce photons of 100 TeV and beyond. The HAWC (High Energy Water Cherenkov) array is the only survey instrument in this energy range. Located on a plateau between two volcanos in Mexico at an altitude of 4100 m, HAWC is able to survey 60% of the sky, and observes 1/6 of the full sky at any moment, day or night. I will discuss the array, its construction and principles of operation, a selection of recent results spanning particle astrophysics to astronomy, and how we are pursuing multi-messenger astronomy to better understand the nature of TeV gamma ray sources.

Faculty Host: Roger Rusack

Thursday, March 7th 2019
10:10 am:
Biophysics Seminar in 120 PAN
No speaker this week.
12:10 pm:
Speaker: Sourabh Chauhan and Evan Tyler
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Marc Pinsonneault, Ohio State University
Subject: Asteroseismology in the Gaia Era

Stellar oscillations are powerful tools for understanding the structure and evolution of stars. With the advent of time domain space missions they can now be measured for large samples of evolved cool stars. The combination of this asteroseismic data, astrometry from Gaia, and large spectroscopic surveys is transforming our understanding of stellar populations and stellar physics. In this talk I review the current state of the art in red giant asteroseismology: both how well we can measure stellar properties using it and how it has changed our understanding of stellar populations and the theory of stellar structure and evolution. I will also discuss the powerful combination of asteroseismology and Gaia, providing two examples: testing the parallax zero point in Gaia with asteroseismology and testing asteroseismic scaling relations with Gaia.

Faculty Host: Evan Skillman

Friday, March 8th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Andre Sieverding, University of Minnesota
Subject: The neutrino process with fully time-dependent supernova neutrino spectra.
12:30 pm:
Speaker: Jessica Turner (Fermilab)
Subject: Leptogenesis via a CP-violating Phase Transition

I will present a mechanism of leptogenesis
which is based on the vacuum CP-violating phase transition. This approach
differs from classical thermal leptogenesis as a specific seesaw model, and
its UV completion, need not be specified. The lepton asymmetry is generated
via the dynamically realised coupling of the Weinberg operator during the
phase transition. This
mechanism provides strong connections with low-energy neutrino experiments.

2:30 pm:
Speaker: Marc Pinsonneault, The Ohio State University
Subject: Stellar Rotation and the Time Domain Revolution

Stellar rotation is intimately connected to some of the most challenging problems in stellar astrophysics: the star and planet formation processes, the origin and generation of magnetic fields, and the transport of angular momentum and associated mixing in stellar interiors. Nearly complete surveys of rotation periods are now available for star clusters and star forming regions down to much lower masses than were available before, and they are challenging our ideas about angular momentum evolution. We have strong evidence that rapid rotation in M dwarfs, traditionally attributed to weak torques, is imprinted early in their evolution, while higher mass stars are born rotating more slowly. I will also present evidence for differences between the rotation of (non-synchronized) binary stars and single stars, and environmental effects on the distribution of stellar rotation rates. Star spots also appear to have a significant impact on stellar structure, inducing significant changes in stellar radii. For the Kepler field, there is evidence for both a maximum age for rotation as a population diagnostic and a possible transition in stellar dynamos below a critical rotation rate. Older stars also appear to be able to spin down to very long rotation periods much earlier than anticipated, with a possible change in behavior near the fully convective boundary. I will close by reviewing the massive data sets that should be available soon and the wide range of potential applications that they will have.

Faculty Host: Evan Skillman
Speaker: Edward Jones-Imhotep, History - York University
Subject: "Theaters of Machines: Breakage, Social Order, and the Lost Histories of the Technological Self"
Refreshments served at 3:15 p.m.
3:35 pm:
Subject: Discussion of three papers

"Examining and contrasting the cognitive activities engaged in undergraduate
research experiences and lab courses" by N. G. Holmes and Carl E. Weinman

"Introductory physics labs: We Can Do Better" by N. G. Holmes and Carl E. Weinman

"Teaching Critical Thinking" by N. G. Holmes, Carl E. Weinman, and D. A. Bonn

Speaker: Lee Penn, CHEM and Diversity Committee

Monday, March 11th 2019
12:15 pm:
Speaker: TBD

Tuesday, March 12th 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Aaron Breneman
Subject: The mysterious post-noon global scale coherence in balloon precipitation signatures
Speaker: Vladimir Cherkassky
Subject: Deliberations on Scientific and Methodological Aspects of Machine Learning

Many diverse fields, such as applied mathematics, statistics, machine learning, data mining, econometrics, bioinformatics etc. are all concerned with estimation of data-analytic models. More recently, due to abundance of data and cheap computing power, machine learning (ML) algorithms have become very popular in various applications, even though many such algorithms are heuristics vaguely motivated by biological/ not mathematical/ arguments. This disconnect (between mathematics and practical applications) may seem strange, given the deep intrinsic connection between mathematics and natural sciences. Well-known historical examples include Kepler’s Laws and (classical) statistical science. The purpose of my talk is to explain various reasons for current disconnect, including (a) conceptual (philosophical) aspects; (b) technical (~mathematical) aspects and (c) non-technical (social) aspects. In particular, my talk will elaborate on different interpretation of philosophical concepts (of deductive and inductive reasoning), in classical statistics and in ML. This methodological difference will be further clarified via several basic assumptions underlying all ML methods – as presented in Vapnik-Chervonenkis (VC) learning theory. Further, I will discuss several ‘non-standard’ inductive problem settings (i.e., different from standard supervised learning) that often enable better generalization with finite training data.

Faculty Host: Vuk Mandic

Wednesday, March 13th 2019
1:25 pm:
Speaker: Oleg Starykh, University of Utah
Subject: Collective modes of magnetized spin liquids

The search for the enigmatic quantum spin liquid (QSL) state has switched into high gear in recent years. Amazing experimental progress has resulted in several highly promising QSL materials such as ZnCu3(OH)6Cl2, YbMgGaO4, and NaYbO2, to list just a few. All of these quasi-two-dimensional materials are characterized by a broad continuum of spin excitations observed in neutron scattering experiments. Unfortunately many, if not all, of these QSL candidates suffer from the presence of significant substitutional disorder which often tends to strongly broaden inelastic neutron spectra and thus calls into question the QSL interpretation of the experimental data. It is therefore incumbent upon the theoretical community to identify specific experimental signatures, more detailed than a “broad continuum” arguments, that evince the unique aspects of spin liquid states of magnetic matter.

In this talk I focus is on the prominent metal-like magnetic insulators – U(1) quantum spin liquids with spinon Fermi surface – excitations of which are represented by neutral spin-1/2 fermions (spinons) and emergent gauge fields. The gauge field mediates strong interactions between spinons. We argue that the full effect of this interaction becomes apparent when the spin liquid is partially magnetized by the Zeeman magnetic field. Under this condition, the spectrum of the spin liquid acquires a new transverse collective spin-1 mode, distinct from incoherent particle-hole excitations of the spinon continuum. Despite being located outside the spinon continuum, this novel collective excitation interacts with emergent gauge fluctuations which are responsible for partially damping it.

I present a tentative theory of this collective mode, including its dispersion, lifetime and other spectral characteristics, and identify conditions needed for its experimental observation. Collective properties of Dirac spin liquids, in which spinon bands form relativistic cone dispersion, will be described as well.

Faculty Host: Andrey Chubukov

Thursday, March 14th 2019
12:10 pm:
Speaker: Nathan Eggen and Larry Rudnick
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Alexander Grosberg, New York University
Subject: Statistical Mechanics of Active Particles

Active particles are the ones having a source of energy to drive them, in addition to the usual Brownian motion. It could be swimming bacteria, or artificial swimmers of various kinds. Statistical mechanics of such out-of-equilibrium systems presents many steep challenges and features many unexpected phenomena. While energy barriers is a staple in physics (Boltzmann limit), force barriers are important for active particles (Sisyphus limit), leading to rectification of random walks, repulsive depletion, etc. Activity can also cause separation of active particles from passive ones even when there is no energetic preference for segregation. The latter effect is particularly strong for polymers, promising interesting applications in the physics of cell nucleus.

Faculty Host: Boris Shklovskii

Friday, March 15th 2019
11:00 am:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: Aleksey Cherman, University of Minnesota
Subject: TBD
12:20 pm:
Speaker: Hanteng Wang
Subject: Many Body Anderson Transition in a deformed Sachdev-Ye-Kitaev model
12:30 pm:
Speaker: Aleksey Cherman (U. Minnesota)
Subject: Comments on Higgs-confinement complementarity and phase transitions
2:30 pm:
Speaker: Emil Rivera-Thorsen, University of Oslo
Subject: A Series Of Fortunate Events: The discovery of a unique, lensed Lyman-continuum leaking galaxy at z=2

"The brightest known gravitationally lensed galaxy is arguably also among the most interesting.
Discovered as part of the Planck Foreground Project and included in the Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas (MEGaSaURA), it is a young, dusty, and very bright starburst at z=2.4. Due to a fortunate alignment of lensing cluster galaxies, it is found in no less than 12 image-plane copies along four major arc segments. A theoretically predicted, but not previously observed, triple-peaked Lyman-alpha emission line profile has revealed that a narrow, empty channel through the neutral medium is aligned with the line-of-sight to Earth, giving us a so far unique, direct view at the young OB stars in the galaxy's most luminous cluster complex. The clear line of sight to the young star clusters has allowed the brightest and best resolved detection of escaping, ionizing Lyman-continuum radiation yet observed at redshifts beyond 0.5, even rivaling some of the local-Universe detections in brightness. The lines of sight traced by the multiply imaged ionizing radiation also provides a direct probe into intergalactic HI on transverse scales at least an order of magnitude smaller than so far probed by close quasar pairs.
In this talk, I will present our findings so far, discuss some of the implications for our knowledge of the radiative transfer and escape of Lyman-alpha and ionizing photons, and show some further puzzling aspects of the galaxy and how they may point us to further research."

There will be no colloquium this week
3:35 pm:
To be announced.
Speaker:  Fernando Luis de Araujo Machado, Departamento de Física, Universidade Federal de Pernambuco
Subject: Symmetric and anti-symmetric contributions in mixed spin-current effects in a Si/Ta/Py/NiO/Pt nanostructure

Spin-currents generated by thermal gradients are efficiently converted into charge-currents by the inverse spin-Hall effect in films of metals presenting strong spin-orbit coupling. The nature of the thermal induced effects depends on the relative orientation among the directions of the spin-current, the applied magnetic field (H), the thermal gradient and the electrical contacts in the metallic film. Mixings in the currents generated by different effects are expected to occur. In this work, the H-dependent anti-symmetric spin-Seebeck effect (SSE) was generated altogether with the symmetric planar Nernst effect in a NiO(100 nm)/Pt(6 nm) nanostructure grown on a 0.5 mm thick Si substrate. A sample holder adapted to a PPMS was used for measuring the voltage in the Pt-film for H in the range ±85 kOe and for temperatures (T) varying from 100 to 300 K. A simple procedure developed for separating the SSE from the planar Nernst effect yielded magnitudes for the SSE in the range ±30 pAcm/K for a temperature different of 10 K across the sample at 300 K. The magnitude of the SSE signal was found to vary with H and T in good agreement with a drift-diffusion magnonic theory. Work supported by CNPq, FACEPE, CAPES and FINEP (Brazilian Agencies).

Faculty Host: E. Dan Dahlberg
4:40 pm:
Speaker: Priscilla Cushman, MIFA

Monday, March 18th 2019
12:15 pm:
Spring Break - no seminar this week.

Wednesday, March 20th 2019
1:25 pm:
Spring Break - No speaker this week.

Thursday, March 21st 2019
10:10 am:
Biophysics Seminar in 120 PAN
Spring Break - No speaker this week.
12:10 pm:
There will be be no Journal Club this week due to spring break
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
There will be be no colloquium this week due to spring break

Friday, March 22nd 2019
Speaker: There will be no seminar this week due to Spring Break.
12:30 pm:
Speaker: SPRING BREAK -- No seminar
2:30 pm:
There will be be no colloquium this week due to spring break
Speaker: Spring break, no seminar this week

Monday, March 25th 2019
12:15 pm:
There will be no seminar this week.
2:00 pm:
Thesis Defense in Tate 201-20
Speaker: Peter Martin, University of Minnesota
Subject: Measuring and Simulating Protein Electron Paramagnetic Resonance Spectra
This is the public portion of Mr. Martin's Thesis Defense. His advisor is David Thomas from the Biochemistry, Molecular Biology, and Biophysics Department.

Tuesday, March 26th 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Trevor Knuth
Subject: Fast time variations in solar flare X-ray flux - A probe for particle acceleration
Speaker: Vipin Kumar
Subject: Physics Guided Machine Learning: A New Paradigm for Modeling Dynamical Systems

Physics-based models of dynamical systems are often used to study engineering and environmental systems. Despite their extensive use, these models have several well-known limitations due to incomplete or inaccurate representations of the physical processes being modeled. Given rapid data growth due to advances in sensor technologies, there is a tremendous opportunity to systematically advance modeling in these domains by using machine learning (ML) methods. However, capturing this opportunity is contingent on a paradigm shift in data-intensive scientific discovery since the “black box” use of ML often leads to serious false discoveries in scientific applications. Because the hypothesis space of scientific applications is often complex and exponentially large, an uninformed data-driven search can easily select a highly complex model that is neither generalizable nor physically interpretable, resulting in the discovery of spurious relationships, predictors, and patterns. This problem becomes worse when there is a scarcity of labeled samples, which is quite common in science and engineering domains.

This talk makes a case that in a real-world systems that are governed by physical processes, there is an opportunity to take advantage of fundamental physical principles to inform the search of a physically meaningful and accurate ML model. Even though this will be illustrated in the context of modeling water temperature, the paradigm has the potential to greatly advance the pace of discovery in a number of scientific and engineering disciplines where physics-based models are used, e.g., power engineering, climate science, weather forecasting, materials science, and biomedicine.

Faculty Host: Vuk Mandic
4:40 pm:
CM Journal Club in Tate 201
Speaker: Yiming Wu
Subject: Transition Metal Dichalcogenide Moire Band

Please find the reading material in the link below:
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.026402


Wednesday, March 27th 2019
1:25 pm:
Speaker: Itamar Kimchi, University of Colorado - Boulder
Subject: Dirty Entangled Quantum Magnets
Faculty Co-Host: Alex Kamenev

Studying quantum entanglement over the past 1--2 decades has allowed us to make remarkable theoretical progress in understanding correlated many-body quantum systems. However electrons in real materials experience random heterogeneities ("dirt") whose theoretical treatment, including strong correlations, has been a challenge. I will describe how synthesizing ideas from quantum information theory, statistical mechanics, and quantum field theory gives us new insights into the role of randomness in 2D correlated quantum spin systems. First I will outline our results on weak bond-randomness in two theoretically controlled cases (valence-bond-solids and classical dimer models) and apply them to random quantum magnets to show that topological defects with free spins necessarily nucleate and control the low energy physics. Second I will describe how the results lead us to conjectures in 2D, and a proved theorem in 1D, of Lieb-Schultz-Mattis-type constraints on all possible low-energy fates of quantum magnets, that hold even with randomness. Third I will describe how the theory predicts a scaling collapse of the temperature and magnetic-field dependence of thermodynamic quantities that is consistent with experimental observations from multiple materials, suggesting that these materials exhibit randomness-driven long range entanglement.

Faculty Host: Fiona Burnell

Thursday, March 28th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Jerome C. Mertz, College of Engineering, Boston University
Subject: Fast, volumetric imaging with microscopes

Fast, volumetric imaging over large scales has been a long-standing challenge in biological microscopy. Camera-based microscopes are typically hampered by the problem of out-of-focus background which undermines image contrast. This background must be reduced, or eliminated, to achieve volumetric imaging. Alternatively, scanning techniques such as confocal and multiphoton microscopy can provide high contrast and high speed, but their generalization to volumetric imaging requires an axial scanning mechanism, which, in general, drastically reduces speed. I will describe a variety of strategies we have developed to enable fast, high-contrast, volumetric imaging over large length scales. These strategies include targeted-illumination widefield microscopy, multi-z confocal microscopy and reverberation multiphoton microscopy. I will discuss the principles of these strategies and present experimental validations.

Faculty Host: Jochen Mueller
12:10 pm:
Speaker: Jin-Ah Kim and Liliya Williams
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Jason Hogan, Stanford University
Subject: Atom interferometry for fundamental physics and gravitational wave detection

In recent years, atom interferometry and atomic clocks have made impressive gains in sensitivity and time precision. The best atomic clocks have stability corresponding to a loss of less than one second in the lifetime of the universe. Matter wave interferometers have achieved record-breaking coherence times (seconds) and atomic wavepacket separations (over half a meter), resulting in a significant enhancement in accelerometer and gravity gradiometer sensitivity. Leveraging these advances, atomic sensors are now poised to become a powerful tool for discovery in fundamental physics. I will highlight ongoing efforts to test aspects of general relativity and quantum mechanics, and search for new fundamental interactions. A particularly exciting direction is gravitational wave detection. I will describe the Mid-band Atomic Gravitational wave Interferometric Sensor (MAGIS) proposal, which is targeted to detect gravitational waves in a frequency band complementary to existing detectors (0.03 Hz – 10 Hz), the optimal frequency range to support multi-messenger astronomy. Finally, I will discuss MAGIS-100, a 100-meter tall atomic sensor being constructed that will serve as a prototype of such a detector, and will also be sensitive to proposed ultra-light dark matter (scalar and vector couplings) at unprecedented levels.

Faculty Host: Roger Rusack

Friday, March 29th 2019
11:00 am:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: James Austin Harris, Oak Ridge National Lab
Subject: The multidimensional character of nucleosynthesis in core-collapse supernovae

The intrinsically multi-dimensional neutrino-driven explosion mechanism of core-collapse supernovae (CCSNe) is notoriously difficult to model self-consistently.

As a matter of either computational expediency or necessity, nuclear burning, when included at all, is traditionally constrained to a small reaction network consisting only of the (α,γ) reactions necessary in linking 4He to 56Ni.

Feedback between the evolving hydrodynamics and changing composition, and resulting energy generation, precludes the deficiencies of this simplification from being entirely resolved with post-processing calculations.

Using a much more realistic, in situ reaction network capable of accurately tracking nuclear energy generation and neutronization, we examine the nucleosynthesis in multidimensional, self-consistent, neutrino-driven supernova models.

We find differences between the in situ and post-processing approaches, indicating that such rigor in evolving the nuclear composition is needed to accurately calculate the nucleosynthesis of matter that has been ejected from the inner regions of the explosion mechanism.

This has implications for some of the most interesting nucleosynthetic processes in CCSNe, specifically α-rich and α-poor freeze-out, which produces several isotopes particularly relevant to observations (e.g.44Ti, 48Ca, and 92Mo).

12:20 pm:
Speaker: Zhen Jiang
Subject: The temperature and doping dependence of the inverse spin Hall effect in n-GaAs
12:30 pm:
Speaker: Vitaly Vanchurin (U. Minnesota, Duluth)
Subject: A quantum-classical duality and emergent space-time

We consider the quantum partition function for a system of quantum spinors and then derive an equivalent (or dual) classical partition function for some scalar degrees of freedom. The coupling between scalars is non-trivial (e.g. a model on 2-sphere configuration space), but the locality structure of the dual system is preserved, in contrast to the imaginary time formalism. We also show that the measure of integration in the classical partition function can be formally expressed through relativistic Green's functions which suggests a possible mechanism for the emergence of a classical space-time from anti-commutativity of quantum operators.

2:30 pm:
Speaker: Vuk Mandic
Subject: Observing the Universe with Gravitational Waves

Since 2015 the LIGO and Virgo gravitational-wave detectors have observed 10 collisions of black hole pairs and one merger of two neutron stars. In addition to enabling unprecedented tests of the theory of General Relativity, these discoveries introduced a new way of observing the universe. While the traditional telescopes observe the universe using electromagnetic waves (i.e. light), LIGO and Virgo do so by measuring tiny ripples in space-time produced by accelerating massive objects moving at speeds near the speed of light. Using the two types of observations together, as was done in the case of the binary neutron star merger, opens a variety of new possible studies ranging from formation mechanisms for the heaviest elements in the periodic table to novel measurements of the expansion rate of the universe. I will describe how these discoveries were made, and I will discuss their implications as well as the exciting future prospects in the field of gravitational waves.

Faculty Host: Evan Skillman
Speaker: Lynn Nyhart, History - University of Wisconsin - Madison
Subject: The Politics of Popular Physiology in Germany in the 1840s and 50s
Refreshments served at 3:15 p.m.
3:35 pm:
To be announced.
4:40 pm:
Speaker: Roger Rusack, High Energy

Monday, April 1st 2019
12:15 pm:
Speaker: Nicholas Mast, UMN
Subject: CDMS Detector Characterization

Tuesday, April 2nd 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Sophie Musset
Subject: Energetic electrons in connection with solar coronal jets

Flare-associated coronal EUV jets outline open magnetic field lines providing an escaping path to the interplanetary medium for particles accelerated during solar flares. Several studies have shown an observational link between coronal jets (observed in EUV or soft X-rays) and type III radio bursts, produced by escaping beams of energetic electrons, or in-situ energetic electron events. In a few events, coronal jets have also been associated with X-ray emitting energetic electrons during flares. However, the likelihood of the association of energetic electrons to coronal jets as well as the link between jet properties and electron properties has not been investigated on a large sample of events.

I will present a statistical study of the link between X-ray producing energetic electrons observed with RHESSI and the associated coronal EUV jets by looking at their relative timing, as well as their spatial and spectral characteristics. We found non-thermal X-ray emission in only 1/4 of our events, which were not necessarily the most energetic flares or jets. I will discuss the statistical distribution of properties of jets and associated flares in the context of jet modelling.

Speaker: Mingyi Hong
Subject: Recent Advances in Adversarial Machine Learning

Recently, it has been observed that machine learning algorithms and models, especially deep neural networks, are vulnerable to adversarial examples. For example, in image classification problems, one can design algorithms to generate adversarial examples for almost every image with very small human-imperceptible perturbation. In this talk, we will give an introduction to recent advances in designing adversary examples for machine learning models. In particular, we will show that how different types of system design, and optimization methods, can be used to build powerful black-box adversarial attacks for existing machine learning models. Our focus will be given to generic algorithm design, as well as to illustrating the connections and empirical performance of different approaches.

4:40 pm:
CM Journal Club in Tate 201
Speaker: Dmitry Chichinadze
Subject: High temperature superconductivity in hydrogen compounds at high pressure

Wednesday, April 3rd 2019
Speaker: Graeme Luke, McMaster University
Subject: Exotic Probes and Extreme Conditions Reveal New States of Quantum Matter

Condensed matter systems provide an exciting laboratory for observing new states of quantum matter via emergence, where the collective behavior of electrons results in quasi-particles with fractional statistics, spin-charge separation, magnetic monopoles and Majorana fermions (particles that are their own anti-particles). I will describe how we design and synthesize new quantum materials that can host these exotic new states of matter and then use a variety of experimental techniques including muon spin relaxation and neutron scattering to probe their properties.

Faculty Host: Martin Greven
Speaker: Graeme Luke, McMaster University
Subject: Exotic Probes and Extreme Conditions Reveal New States of Quantum Matter

Condensed matter systems provide an exciting laboratory for observing new states of quantum matter via emergence, where the collective behavior of electrons results in quasi-particles with fractional statistics, spin-charge separation, magnetic monopoles and Majorana fermions (particles that are their own anti-particles). I will describe how we design and synthesize new quantum materials that can host these exotic new states of matter and then use a variety of experimental techniques including muon spin relaxation and neutron scattering to probe their properties.

7:00 pm:
Speaker: Robert Kennicutt, University of Arizona and Texas A&M University
Subject: The Cosmic Ecosystem:  Connecting the Life Cycles of Stars, Galaxies, and the Universe

The past decade has seen a quiet revolution in our understanding of the "Origins" questions in astronomy, namely how galaxies, stars, planets, the chemical elements, and the universe itself were formed and evolve over the history of time.  Observations of galaxies with the Hubble Space Telescope and a variety of ground-based instruments have allowed us to reconstruct an empirical history of galaxies from the Big Bang to the present, and the introduction of sophisticated numerical models have transformed our theoretical understanding this evolution.
 
Remarkably, the same theory for the evolution and structure of our universe, in which dark matter and dark energy play the dominant roles, when extrapolated to smaller scales also reproduces most of the observed properties of galaxies over cosmic time.  In this picture the key physical processes take place over an enormous dynamic range of physical scales, from cosmological scales to those of individual massive stars and black holes, all closely linked and interacting in a what can be regarded as a self-regulating ecosystem.  This talk will describe how the observational, theoretical, and numerical pieces of this new picture came together, and will highlight some of the current questions, challenges, and exciting opportunities which lie ahead.

About the speaker: Robert Kennicutt is Professor of Astronomy at the University of Arizona and at Texas A&M University, and Executive Director of the Mitchell Institute for Fundamental Physics and Astronomy at TAMU. He is an Emeritus Professor at the University of Cambridge, where he held the Plumian Professorship in Astronomy and Experimental Philosophy, and also served as Director of the Institute of Astronomy and Head of the School of the Physical Sciences.

Kennicutt earned his PhD degree from the University of Washington, and his first faculty position was in the School of Physics and Astronomy at the University of Minnesota (1980-1988), before moving on to faculty positions in Arizona and Cambridge. He served as Editor-in-Chief of The Astrophysical Journal, and this year will become Co-Editor of the Annual Review of Astronomy and Astrophysics. Together with Fiona Harrison he is co-chairing the National Academy of Sciences Astro2020 Decadal Survey of Astronomy and Astrophysics. Kennicutt’s research focuses on observational extragalactic astronomy and cosmology, including the structure and evolution of galaxies, star formation in galaxies, chemical abundances in the universe, and the extragalactic distance scale. His studies span a wide range of wavelengths from radio to ultraviolet, and from nearby galaxies to distant galaxies observed when the universe was a fraction of its current age. He co-led (with Jeremy Mould and Wendy Freedman) the Hubble Space Telescope Key Project on the extragalactic distance scale, and three were awarded the Gruber Cosmology Prize for this work. Other awards include the AAS/AIP Dannie Heineman Prize in Astrophysics, the Gold Medal of the Royal Astronomical Society, and the NAS Award for Scientific Reviewing. He is a member of the National Academy of Sciences, the American Academy of Arts and Sciences, and is a Fellow of the Royal Society.


Thursday, April 4th 2019
12:10 pm:
Speaker: Karl Young
1:30 pm:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: Amol Vivek Patwardhan, University of Wisconsin-Madison
Subject: Neutrino spin-coherence in a core-collapse supernova environment
NOTE: change of time from previous email.

We examine the prospects for coherent spin-transformations of Majorana neutrinos (i.e., neutrino-antineutrino transformations) in a core-collapse supernova environment. We observe that, under certain conditions, resonant effects can drive substantial neutrino-antineutrino conversion, with potential implications for subsequent flavor evolution as well as the neutron-to-proton ratio (equivalently, the electron fraction) of the material in the supernova envelope. We also investigate a nonlinear feedback mechanism that arises from the coupling between the neutrino distributions and the electron fraction, potentially assisting the stabilization of the resonance.

3:35 pm:
Van Vleck Colloquium in Physics Tate B50
Speaker: Rob Kennicutt, Texas A&M University
Subject: The Schmidt Law at Sixty

Sixty years have passed since Maarten Schmidt's conjecture that star formation in galaxies was closely coupled to gas density, and since that time the Schmidt law has become an indispensable tool for interpreting, modeling, and simulating large-scale star formation in galaxies. Despite its success as a sub-grid "recipe" for the star formation rate, however, we remain far away from an ab initio theory of star formation, or even a clear understanding of the observed scaling laws themselves. This talk will review the current state of our observational understanding of star formation in galaxies, and the complexity which lies beneath the surface of the observed SFR scaling relations. We are witnessing an observational and theoretical renaissance in the subject, as multi-wavelength observations reveal the multi-scale nature of the star formation process and the complex interactions which are taking place between cosmological, gravitational, interstellar, and stellar feedback processes on these different scales. The picture which emerges is one in which the superficially simple star formation scaling laws are manifestations of a highly dynamic, complex, and self-regulating ecosystem in galactic disks.

Faculty Host: Ronald Poling

Friday, April 5th 2019
12:20 pm:
Speaker: Mengqun Li
Subject: The Kitaev magnet beta-Li2IrO3 in a magnetic field
12:30 pm:
Speaker: Raymond Co (U. Michigan)
Subject: Non-Thermal Production of Bosonic Dark Matter

The conventional misalignment mechanism can explain axion dark matter only in a limited mass range and face various difficulties for vector dark matter that we refer to as dark photons. For the former case, we provide a dynamical explanation for an initial condition near the hilltop or the bottom of the potential, which allows for a much wider mass range. Additionally, we propose new dark matter production mechanisms for axions and dark photons via parametric resonance and tachyonic instability, respectively. These ideas expand the parameter space to the regions of interest for the extensive experimental searches.

2:30 pm:
Speaker: Rob Kennicutt, Texas A&M University
Subject: 2020 Decadal Survey
Subject: Author Meets Reader: "Varieties of Continua: From Regions to Points and Back." Authors: Geoffrey Hellman and Stewart Shapiro. Readers: Øystein Linnebo and Gabriel Uzquiano
Refreshments served at 3:15 p.m.
3:35 pm:
Speaker: Richard Diurba, University of Minnesota
Subject: A quantitative investigation of NSF science funding as it relates to US partisan politics with some notes on qualitative big science project observations.
4:40 pm:
Speaker: Marvin Marshak, Particle physics

Monday, April 8th 2019
12:15 pm:
Speaker: Lindsey Bleem, Argonne National Laboratory
Subject: Galaxy Cluster Cosmology with the South Pole Telescope

The South Pole Telescope (SPT) is a 10-meter millimeter-wavelength telescope located at the geographic South Pole, one of the world’s premier sites for millimeter-wave observations. It has been used to survey approximately 1/8 of the sky with arcminute-scale resolution over the course of the 3 surveys: the 2500-square-degree SPT-SZ survey, the 2700-square-degrees SPTpol Extended Cluster Survey, and the 500-square-degree SPTpol main survey (which reached depths of 5.3 uK-arcmin at 150 GHz, 3x deeper than SPT-SZ and 6x deeper than the wide area SPTpol survey). One of the primary objectives of these wide-area surveys has been the construction of a mass-limited sample of galaxy clusters identified via the thermal Sunyaev- Zel’dovich (SZ) effect, through which massive clusters imprint subtle temperature distortions on the cosmic microwave background. The abundance of such clusters is a powerful cosmological probe as it depends sensitively upon both the expansion history of the universe and the growth of density fluctuations. In this talk I will discuss progress analyzing these three datasets including updated cosmological constraints from the initial SPT-SZ cluster sample using weak gravitational lensing data from the Magellan and Hubble Space Telescopes as well as ongoing work from a new project characterizing the strong gravitational lensing properties of these systems in both observations and simulations. The results presented in this talk will be significantly improved with data from the ongoing SPT-3G survey that will identify an order of magnitude more clusters than previous generation SZ surveys.


Tuesday, April 9th 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
To be announced.
Speaker: Dan Frisbie and Kevin Dorfman
Subject: Electrolyte Gated Transistors with Floating Gates as Biosensors

Electrolyte gated transistors (EGTs) are a sub-class of thin film transistors that are extremely promising for biological sensing applications. These devices employ a solid electrolyte as the gate insulator; the very large capacitance of the electrolyte results in low voltage operation and high transconductance or gain when incorporated into an inverter architecture. This talk will describe the fabrication of floating gate EGTs and their use as protein sensors. The floating gate EGT (FG-EGT, or simply FGT) design allows separation of the semiconductor channel from the analyte capture surface. That is, two electrolyte compartments are employed, one that coats an arm of the floating gate and the semiconductor source-drain channel, and the other that coats the capture surface on the other arm of the floating gate and an electrically addressable control gate. The capture surface is coated with aptamers or antibodies that selectively bind the molecular target. Having two separate electrolyte compartments prevents contamination of the semiconductor with the analyte solution and allows optimization of the response of the device independent of surface chemistry. This talk will describe the fundamental operating principles of the FGT and its implementation in a sub-1 V differential amplifier sensor scheme for label-free protein detection. Prospects for generalizing the FGT platform to other analyte classes will also be discussed.

Faculty Host: Vuk Mandic

Wednesday, April 10th 2019
1:25 pm:
Speaker: Vidya Madhavan, University of Illinois - Urbana-Champaign
Subject:  Signatures of 1D dispersing Majorana modes in the proximitized topological surface states of FeSe0.5Te0.5

Majorana fermions can be realized as quasiparticle excitations in a topological superconductor, whose non-Abelian statistics provide a route to developing robust qubits. In this context, there has been a recent surge of interest in the iron-based superconductor, FeSe0.5Te0.5. Theoretical calculations have shown that FeSe0.5Te0.5 may have an inverted band structure which may lead to topological surface states, which can in turn host Majorana modes under certain conditions in the superconducting phase. Furthermore, recent STM studies have demonstrated the existence of zero-bias bound states inside vortex cores which have been interpreted as signatures of Majorana modes. While most recent studies have focused on Majorana bound states, more generally, akin to elementary particles, Majorana fermions can propagate and display linear dispersion. These excitations have not yet been directly observed, and can also be used for quantum information processing. This talk is focused on our recent work in realizing dispersing Majorana modes. I will describe the conditions under which such states can be realized in condensed matter systems and what their signatures are. Finally, I will describe our scanning tunneling experiments of domain walls in the superconductor FeSe0.45Te0.55, which might potentially be first realization of dispersing Majorana states in 1D.

Faculty Host: Martin Greven
To be announced.

Thursday, April 11th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Mark Sanders, Program Director, University of Minnesota Imaging Centers
Subject: Frontiers in Imaging Technologies and Strategies for Researchers at University Imaging Centers

Core facilities are an essential resource in research institutes.The University Imaging Centers (UIC) has instrumentation, staffing expertise available for teaching, training and outreach in the imaging pipeline from experimental design through analysis. The UICs instrumentation list ranges from nano to mesoscales and includes electron microscopy; super-resolution; single and multi-photon confocal microscope systems; and high-content screening (HCS) systems. We have added tissue clearing, light sheet imaging and, coming soon, a mass spectrometry-based imaging platform in mid-2019. At the mesoscale, the UIC is equipped for in vivo small animal imaging providing investigators with bioluminescence, fluorescence, x-ray, µCT, µPET and ultrasound. How the UIC can help you would be our goal.

12:10 pm:
Speaker: Sean Bruton and Hugh Dickinson
3:35 pm:
Speaker: Dimitar Sasselov, Harvard
Subject: Stellar UV Light and the Origins of Life's Building Blocks on Earth and on Exoplanets
Faculty Host: Evan Skillman
7:00 pm:
Speaker: Eliot Quataert, UC Berkeley
Subject: Cosmic Gold: Neutron Star Mergers, Gravitational Waves, and the Origin of the Elements

Scientists have recently developed a new way to `see' the universe, using gravitational waves predicted by Einstein nearly a century ago. These waves can teach us about some of the most exotic objects known, including dead stars known as black holes and neutron stars. Remarkably, they have also helped solve a longstanding puzzle about where in the Universe some of the elements we know and love here on Earth are produced, including uranium, platinum, and even gold. Eliot Quataert will describe the exciting and remarkable new results coming out of our first steps into this new era.


Friday, April 12th 2019
11:00 am:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: Manibrata Sen, Northwestern University
Subject: Supernova neutrino oscillations: the slow, the furious and the fast!

Neutrino flavor conversions are known to play a very important role in core-collapse supernova explosions. Inside a supernova, neutrino density is so large that neutrino-neutrino interactions take place, giving rise to "collective oscillations" occurring with a rate much larger than the usual MSW flavor conversions. In this talk, I would like to discuss some of the interesting aspects of these rapid flavor conversions, and the impact they can have on supernova explosions and nucleosynthesis. Finally, I will also talk about a simple way of diagnosing the presence of these instabilities in large scale numerical simulations.

12:20 pm:
Speaker: Protyush Sahu
Subject: Spin orbit torque characterization in amorphous Gd-alloyed bismuth selende thin films
12:30 pm:
Speaker: Erich Poppitz (U. Toronto)
Subject: Higher symmetry ’t Hooft anomalies and domain walls

We first review the zero-form/one-form ’t Hooft anomaly matching conditions, using the example of the charge-Q massless Schwinger model. This is the simplest quantum field theory with such anomalies and their manifestation can be seen from different points of view. We will then argue that the Q=2 case and its various generalizations are relevant for the physics of domain walls in four-dimensional super-Yang-Mills theory and adjoint QCD and will show how various aspects of bulk/domain wall interactions found earlier via string theory can be seen in a purely field theoretic setting.

2:30 pm:
Speaker: Eliot Quataert, UC Berkeley
Subject: What Happens When a Massive Star Fails (Sort of) to Explode?

There are observational and theoretical reasons to suspect that up to
10s of percent of massive stars that undergo core-collapse at the end
of their lives fail to explode in a canonical energetic supernova
explosion. In this talk I will describe what transpires in such
nominally failed supernovae and its importance for understanding the
masses and spins of black holes (e.g., detected by LIGO). I will also
describe how 'failed' supernovae may manifest themselves
observationally in time-domain surveys.

2:30 pm:
CM Journal Club in PAN 110
Speaker: M. Kiefer-Emmanouilidis
Subject: Current reversals in the Bose-Hubbard chain with local particle loss
Note change of time and day, this week only.

Many-body interactions lead to unexpected effects in the open
Bose-Hubbard model. When the model is subjected to local loss, particle
currents are induced. Away from the dissipative site the currents start
to reverse their direction at intermediate and long times. This leads
to a metastable state with a total particle current pointing away from
the dissipative site. We studied the model numerically by combining
a quantum trajectory approach with a density-matrix renormalization
group scheme. An alternative equation of motion approach based on
an effective fermion model shows that the reversal of currents can be
understood qualitatively by the creation of holon-doublon pairs at the
edge of the region of reduced particle density. The doublons are then
able to escape while the holes move towards the dissipative site.

Some keywords for the talk:
1D quantum chains, Bose-Hubbard model, Markovian open systems,
Matrix product states/ Density Matrix Renormalization Group
, Metastable states, Lindblad master equation

Papers and readings:
His results have been published on
M. Kiefer-Emmanouilidis & J. Sirker, Current reversals and metastable states in the infinite Bose-Hubbard chain with local particle loss. PhysRevA.96.063625 (2017).

The following books give a quite good introduction to open systems:
1. Breuer, Heinz-Peter; Petruccione, F. (2002). The Theory of Open Quantum Systems. Oxford University Press
2. Carmichael, Howard. An Open Systems Approach to Quantum Optics
3. Further there is a quite good but mathematically summary here
https://en.wikiversity.org/wiki/Category:Open_Quantum_Systems/Lectures

3:35 pm:
Speaker: Phil Buhlmann, Dept. of Chemistry, University of Minnesota
Subject: Addressing Stress and Mental Health in a PhD Program

Our department makes stress and mental health a major point of attention for our graduate program. Our approach is not to lower the bar for the PhD degree. Instead, we strive to eliminate unnecessary sources of stress and create conditions in which students feel engaged, supported, and empowered. The key to our initiative lies in contributions from students, staff, faculty, and the university health services. While only professionals can provide therapy, three chemistry faculty members serve as Mental Health Advocates and help to direct faculty, staff, and students to relevant resources. Students formed the group Community of Chemistry Graduate Students (CCGS), which organizes regular events on physical and mental health and stress management. To reach out to students outside the department, the CCGS also prepared a range of insightful videos on the topics of mental health in graduate school, academic success, and the transition into a job after graduate school. CCGS representatives and the
director of graduate studies also worked with university health services to develop biannual surveys that help us better understand sources of stress. The survey taught us a lot about our students and, within a relatively short time, allowed us to improve a range of graduate program procedures.

Speaker: Nancy Sims, UMN Libraries
Subject: Copyright Triage

Monday, April 15th 2019
12:15 pm:
Speaker: Keith Bechtol, University of Wisconsin - Madison
Subject: Dark Matter Science in the LSST Era

Astrophysical observations probe the physics of dark matter through its impact on structure formation throughout cosmic history. On large scales, current observational data are well described by a simple model of stable, non-relativistic, collisionless, cold dark matter (CDM). However, many viable theoretical models of dark matter predict deviations from CDM that are testable with current and future observations. Fundamental properties of dark matter — e.g., particle mass, self-interaction cross section, coupling to the Standard Model, and time evolution — can imprint themselves on the macroscopic distribution of matter in a detectable manner. With supporting theoretical efforts and follow-up observations, LSST will be sensitive to several distinct classes of dark matter models, including particle dark matter, field dark matter, and compact objects. I will discuss several astrophysical probes of dark matter microphysics that can be pursued with LSST, as well as synergies between LSST and other astronomical, cosmological, and particle physics experiments of the 2020s.


Tuesday, April 16th 2019
11:15 am:
Speaker: Joe Redish, University of Maryland, College Park
Subject:  Learning Each Other's Ropes: Negotiating interdisciplinary authenticity
Please note the date, time and room change of this seminar for this week only.

Very few students who take introductory physics are physics majors.
They major in Engineering, Biology, Chemistry, Mathematics, or
Architecture to name a few of the many disciplines represented in the
introductory physics class. All of these students are required to
take physics which is viewed by the faculty of those disciplines as
useful, an outlook often not shared by their students. This seminar
will discuss the communication difficulty between physics and other
STEM fields that impacts any attempt to redesign introductory physics
courses that build closer links to students’ major fields. My recent
experience has been in building a physics course for Biology majors.
In doing so, I have been engaged in a multiyear conversation with a
biologist interested in including more physics in his biology course.
These extended discussions have led us both to a deeper understanding
of each other's discipline and to significant changes in the way we
each think about and present our classes.

Faculty Host: Kenneth Heller
1:25 pm:
Space Physics Seminar in 5th floor Walter Library
Subject: MSI Poster session Physical Sciences 2:15-3
Speaker: Andrew Zolli, Vice President, Global Impact Initiatives, Planet
Subject: Using Space to Help Life on Earth: How the Small Satellite Revolution and AI are Transforming How We See and Understand Our World
PLEASE NOTE THE SEMINAR FOR THIS WEEK IS CANCELLED.

A revolution in low-cost, space-based remote sensing, combined with new analytical tools in machine learning, computer vision and artificial intelligence, are creating unprecedented new opportunities for tackling the world’s toughest challenges.

Andrew Zolli is the Vice President for Global Impact Initiatives at Planet (www.planet.com). Started by three NASA engineers, Planet has deployed the largest constellation of Earth-observation satellite in history. Together, these satellites image the entire surface of the Planet, every day, in high resolution. The resulting data holds transformational potential for basic science, and for a host of global challenges, including monitoring deforestation, agriculture and cities, tracking migration, mitigating the effects of climate change, speeding disaster response, and delivering planetary health, among others.

In this talk, Andrew will share lessons from the forefront of the New Space renaissance, as well as breakthrough new remote sensing applications being used right now around the world, and describe how new agile manufacturing and development technologies are accelerating the pace of innovation.

Faculty Host: Vuk Mandic

Wednesday, April 17th 2019
1:25 pm:
Speaker: Jorn Venderbos, University of Pennsylvania
Subject: Many-body band inversions

Topological materials are a new class of quantum materials with remarkable properties, which are rooted in the topology of the ground state wave function. Our understanding of topological electronic phases, in particular free fermion phases, relies on one of the central paradigms of modern electron band theory: the notion of a band inversion. In this talk I will first review what a band inversion is, and then describe our attempt to construct a many-body generalization of the band inversion transition, providing a new perspective for interacting topological phases. In particular, I will introduce a special class of band inversions in two dimensions for which interactions are expected to determine the fate of the transition and present evidence that these provide promising venues for a strongly correlated fractionalized fluid of electrons and holes. I will describe possible routes to material realizations and will discuss connections to new types of topological semimetals in three dimensions as well as superconductors.

Faculty Host: Rafael Fernandes

Thursday, April 18th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Erin Sheets, Associate Professor, University of Minnesota, Duluth, Department of Chemistry and Biochemistry
PLEASE NOTE THAT THE SEMINAR FOR THIS WEEK IS CANCELLED
Faculty Host: Elias Puchner
12:10 pm:
Speaker: Mike Makmur and Vihang Mehta
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Ian Tregillis, Los Alamos National Laboratory
Subject: Verification & Validation of a Richtmyer-Meshkov Instability Based Ejecta Source Model, or, Why Should Los Alamos Care About a Freshman Physics Problem?

Computational physicists are commonly faced with the task of resolving discrepancies between the predictions of a complex, integrated multi-physics numerical simulation and corresponding experimental datasets. Such efforts commonly require a slow iterative procedure. However, a different approach is available in cases where the multi-physics system of interest admits closed-form analytic solutions. In this situation, the ambiguity is broken into separate consideration of theory-simulation comparisons (issues of verification) and theory-data comparisons (issues of validation). We demonstrate this with the specific example of a fluid- instability based ejecta source model (“RMI+SSVD”) under development at Los Alamos National Laboratory and implemented in FLAG, a Los Alamos continuum mechanics code. For a specific (but wide-ranging) class of explosively driven metal coupon experiments, the ejecta model prediction inherently reduces to a one-dimensional vacuum kinematics problem. This enables us to compute, purely analytically, piezoelectric ejecta mass measurements suitable for “apples-to-apples” comparisons to both simulated and measured datasets. Thus, studying the solution to a very simple yet overlooked problem yields rich and concrete insights into performance of the model, its strengths and shortcomings, as well as strategies for improving it. These conclusions are made quantitative through the introduction of a straightforward yet rigorous “compatibility score” metric incorporating published measurement uncertainties on relevant experimental parameters.

Faculty Host: Thomas W. Jones

Friday, April 19th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
To be announced.
11:00 am:
Speaker: Ritika Dusad, Cornell University
Subject: Magnetic Monopole Noise

Magnetic monopoles are hypothetical elementary particles exhibiting quantized magnetic charge m_0=±(h⁄(μ_0 e)) and quantized magnetic flux ϕ_0=±h/e. A classic proposal for detecting such magnetic charges is to measure the quantized jump in magnetic flux Φ threading the loop of a superconducting quantum interference device (SQUID) when a monopole passes through it. Naturally, with the theoretical discovery that a plasma containing equal numbers of emergent magnetic charges 〖±m〗_ should exist in several lanthanide-pyrochlore magnetic insulators including Dy_2Ti_2O_7, this SQUID technique was proposed for their direct detection. Experimentally, this has proven extremely challenging because of the high number density, and the generation-recombination (GR) fluctuations, of the monopole plasma. Recently, however, theoretical advances have allowed the¬ spectral density of spontaneously generated magnetic-flux noise S_Φ (ω,T) due to a thermally generated plasma of magnetic monopoles 〖±m〗_to be predicted for Dy2Ti2O7. I will describe development of a high-sensitivity, SQUID based flux-noise spectrometer, and consequent measurements of the frequency and temperature dependence of S_Φ (ω,T) for Dy2Ti2O7 samples. Virtually all the elements of S_Φ (ω,T) predicted for a magnetic monopole plasma, including the existence of intense magnetization noise and its characteristic frequency and temperature dependence, are detected directly. Moreover, measured correlation functions C_Φ (t) of the magnetic-flux noise Φ(t) reveal that the motion of magnetic charges is correlated. A final striking observation is that, since the GR time constants τ(T) are in the millisecond range for Dy2Ti2O7, magnetic monopole flux noise amplified by the SQUID is audible to human perception.

Faculty Host: Vlad Pribiag
12:20 pm:
Speaker: Dan Phan
Subject: Modification of Tc in Low Carrier Density Superconductors
12:30 pm:
Speaker: Matt Reece (Harvard U.)
Subject: The Weak Gravity Conjecture and Photon Masses

I will review the Weak Gravity Conjecture (WGC) and related ideas (such as the Swampland Distance Conjecture and “tower” versions of the WGC), which aim at characterizing generic properties of quantum gravity theories that can be used to diagnose when a low-energy effective field theory cannot be completed into a consistent gravitational theory. As one application, I will explain how arguments based on these conjectures suggest that a theory of quantum gravity requires the photon to be exactly massless.

2:30 pm:
Speaker: Peter Garnovich, University of Notre Dame
Subject: The Spin Cycle: Rapidly Rotating Magnetized White Dwarfs in Close Binaries

The most dynamic types of cataclysmic variable stars are 0nes where the accreting white dwarf is magnetized and its rotation is not locked the binary orbital period. These are often called intermediate polars (IPs) or asynchronous polars (APs) depending on the white dwarfs field strength. I will discuss two of the most exciting and nearby polars and their recent activities. FO Aquarii has been dubbed the "King of the IPs" because of the large amplitude variations produced by the 20 minute spin period of its white dwarf. Recently it has gone into a series of low states that reveal a variety of periodicities. The low states may be related to the long-term evolution of the spin rate of its white dwarf. The second star, AR Scorpii, is a one-of-a-kind white dwarf pulsar. This unique system was identified only four years ago, and the source of its light variations are still in dispute.

Faculty Host: Patrick Kelly
Speaker: Jenna Tonn, History - Boston College
Subject: Being "One of the Boys": Manliness and Experimental Zoology in Boston
Refreshments served at 3:15 p.m.
3:35 pm:
The seminar will be on Tuesday this week. Note change of time and date next week only.
4:40 pm:
Speaker: Paul Crowell, Condensed Matter

Monday, April 22nd 2019
12:15 pm:
Speaker: Andrew Wetzel, UC Davis
Subject: Simulating the Milky Way and its Satellites

I will present the Latte suite of cosmological zoom-in baryonic simulations that model the formation of Milky Way-like galaxies at parsec-scale resolution, using the FIRE (Feedback in Realistic Environments) model for star formation and feedback. First I will discuss the formation of the Milky Way, including the origin of its thin+thick stellar disk morphology, new insights into the elemental abundances of its stellar populations, and connections to recent Gaia observations of the stellar halo. The Latte simulations also self-consistently resolve the formation of satellite dwarf galaxies around each Milky Way-like host. These low-mass galaxies have presented significant challenges to the cold dark matter model, but I will show progress in addressing the "missing satellites" and "too-big-to-fail" problems. Finally, I will discuss synthetic Milky Way surveys that we have created from the Latte simulations, which are publicly available to provide theoretical modeling insight for the era of Gaia.

2:00 pm:
FTPI Special Seminar in Tate 201-20
Speaker: Anthony Zee, UC Santa Barbara
Subject: Some Speculations on the Cosmological Constant Paradox

We discuss some wildly speculative thoughts about the vexing unsolved problem about the cosmological constant paradox.

Faculty Host: Alex Kamenev

Tuesday, April 23rd 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Sheng Tian
Subject: The azimuthal propagation of dipolarization in the inner-magnetosphere
Speaker: Jarvis Haupt and Mike Garwood
Subject: Bringing Compact High-Field MRI Systems to Life through Novel Methods that Tolerate Extreme Field Inhomogeneity

MRI is critically important for understanding the human brain and for diagnosing neurological disease, yet is currently inaccessible to ~90% of the world’s population. One way to increase the accessibility of MRI is to decrease the size of the magnet, making it lighter and transportable, but this comes at the cost of greatly diminished uniformity of the main magnetic field, B0. Thus, the main obstacle to making a small MRI scanner comes down to the question: Is it possible to make high quality MR images with a highly inhomogeneous B0? To accomplish this, the basic approach to performing MRI must change; specifically, how spatial information is encoded, and then, how the resulting MRI signals can be reconstructed into high resolution images. In this talk we will discuss the unique challenges and opportunities that arise within our approach, which uses spatiotemporal, frequency-swept pulses to excite MRI signals over broad frequency ranges and a model-based image reconstruction algorithm that deciphers the spatiotemporal information in the MRI signals.

Faculty Host: Vuk Mandic

Wednesday, April 24th 2019
1:25 pm:
Speaker: Ming Yi, Rice University
Subject: Role of Orbital Physics in Iron Chalcogenide Superconductors

Electron correlation effects give rise to a variety of emergent phenomena in quantum materials—high temperature superconductivity, electronic nematicity, Mott insulating phase, magnetism. The family of Fe(Se,Te) superconductors plays a remarkable host to all of these phenomena in different parameter regimes. In this talk, I will present angle-resolved photoemission results on two aspects of electron correlation effects in this material family—i) orbital-selective Mott insulating behaviors towards the FeTe end of the phase diagram, and ii) electronic nematicity in completely detwinned FeSe. Both examples showcase the phenomenal way that correlation effects rewrite the low energy electronic states of a material system, and reveal the exceptional role the orbital degree of freedom plays in composing the fundamental physics in iron chalcogenide superconductors.

Faculty Host: Rafael Fernandes
Speaker: Chris White, Higgs Centre for Theoretical Physics, University of Edinburgh
Subject: Reactor Neutrino Physics from the PROSPECT Experiment

PROSPECT, the Precision Oscillation and Spectrum Experiment, is a reactor antineutrino experiment designed to search for eV-scale sterile neutrinos and measure the spectrum of antineutrinos from highly-enriched 235U at the High Flux Isotope Reactor (HFIR). PROSPECT uses a 4-ton, segmented 6Li-doped liquid scintillator detector to make a high-resolution measurement of the prompt energy spectrum from inverse beta decay on protons. An optical and radioactive source calibration system integrated into the active detector volume is used to characterize the optical and energy response of all detector segments. I will discuss the construction and characterization of the PROSPECT detector and report on PROSPECT’s first measurement of the energy spectrum associated with reactor antineutrinos.


Thursday, April 25th 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Siddarth Karuka, PhD student in Jochen Mueller’s lab, School of Physics and Astronomy
Subject:  Progress Report: Axial Super-Resolution with Two-Photon Microscopy

The Nuclear Envelope (NE) is a ~40 nm space enclosed by the Outer and Inner Nuclear Membrane (ONM and INM), that separates the nucleus from the cytoplasm. Although recent research has identified the NE as a critical signaling hub for a cell, it remains difficult to study with current fluorescence microscopy techniques that are limited to 50 nm axial resolution. To study systems like these, we have developed the dual color z-scan (DC Z-Scan) technique that can achieve axial resolution on the order of a nanometer. We first demonstrate the technique on a supported lipid bilayer, and then use it to measure the thickness of NE, distinguish proteins that reside on the ONM vs INM and study the translocation kinetics of these proteins.

12:10 pm:
Speaker: Trevor Knuth and Evan Skillman
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Sanjay Reddy, University of Washington
Subject: Neutron stars come of age

About 50 years after their discovery, neutron stars are poised to take center stage in this era of multi-messenger astrophysics. In the not-so-distant-future (10-20 years) it is likely that next generation gravitational wave observatories will detect gravitational waves from hundreds of mergers involving neutron stars every year. I will highlight advances in theory and mention some key observations that have already provided fundamental new insights about neutron star properties and their central role in nuclear astrophysics. I will discuss how neutron stars, and extreme phenomena involving them, can serve as laboratories to study phase transitions in dense matter, nucleosynthesis, and dark matter in the coming decades.

Faculty Host: Joseph Kapusta

Friday, April 26th 2019
11:00 am:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: Sanjay Reddy, University of Washington
Subject: “Hunting for dark matter with neutron stars”

I will discuss new strategies to discover or constrain dark matter using neutron stars and gravitational waves.

12:20 pm:
Speaker: Fei Chen
Subject: Signatures of Superconducting Fluctuations on the Nonlinear Susceptibility of Layered Superconductors
12:30 pm:
Speaker: Grant Remmen (UC Berkeley)
Subject: Entropy Bounds on Effective Field Theory from Rotating Dyonic Black Holes
2:30 pm:
Speaker: There will be no colloquium today
Faculty Host: Charles E. Woodward
Speaker: Olivia Weisser, History - University of Massachusetts
Subject: Republic of Venus: Shopping for Venereal Cures in Early Modern London
Refreshments served at 3:15 p.m.
3:35 pm:
Speaker: Autumn Brower, University of Minnesota
Subject: How computer coaches impact math anxiety in introductory physics students
PLEASE NOTE THE SEMINAR IS IN ROOM PAN 130 THIS WEEK

Math anxiety is a multidimensional construct that can
manifest at cognitive, affective, behavioral and physiological levels.
With the increased use of technology in our society, there has been an
increased need for more technology in educational settings. This
presentation looks at the role of technology—in the form of online
physics computer coaches—to better understand math anxiety patterns in
introductory physics students. It considers the limitations of the
data collected on the coaches in the context of math anxiety. It also
looks at how math anxiety can be turned into a positive quality
through the use of a model on human performance and how that can be
applied to learning, teaching, and education.

Speaker: Career Advisory Board Visit + Meet, no seminar this week.

Monday, April 29th 2019
12:15 pm:
Speaker: Patrick Kelly, UMN

Tuesday, April 30th 2019
Speaker: TBD
Subject: TBD
Faculty Host: Vuk Mandic

Wednesday, May 1st 2019
1:25 pm:
Speaker: Jack Harris, Yale University
Subject: A pedagogical introduction to the emergence of topology in non-Hermitian dynamics

A collection of coupled linear oscillators is widely regarded as a trivial physical system. Nevertheless, in recent years it has become evident that weak loss (or gain) in these systems can result in a variety of qualitative surprises - even in the purely linear regime. Effects that have attracted considerable attention include: PT symmetry breaking, exceptional points, non reciprocity, and topological control. I will describe a simple framework that unites these "non-Hermitian" effects and explains why topology emerges generically in damped coupled linear oscillators. I will discuss the application of these concepts in classical systems and in quantum systems. Lastly, I will describe an optomechanical experiment that offers a natural way to realize generic non-Hermiticity.

Faculty Host: Paul Crowell

Thursday, May 2nd 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: TBD
12:10 pm:
Speaker: Tom Jones and Jamie Cheshire
3:35 pm:
Speaker: Jack Harris (Yale University)
Subject: Quantum optomechanics with superfluid helium
Note change of room for this week only. Refreshments in atrium after the Colloquium.

To observe quantum effects in the motion of macroscopic objects typically requires high-precision readout, low temperature, and low optical and mechanical loss. Superfluid helium offers many advantages in these regards. I will describe two optomechanics experiments based on superfluid helium. In the first, the superfluid fills a Fabry-Perot optical cavity. The cavity is used to monitor the quantum fluctuations of the superfluid's acoustic modes. This system is amenable to single photon/phonon detection schemes, and so may provide a route to more exotic quantum effects in massive objects. The second experiment uses magnetic levitation to suspend a mm-scale drop of superfluid in vacuum. I will describe preliminary measurements of the drop's formation, trapping, and evaporative cooling, and of the drop's mechanical resonances and optical resonances.

Faculty Host: Paul Crowell
4:00 pm:
A.O.C. Nier Lecture in B50 Tate
Speaker: Kenneth A. Farley, W.M. Keck Foundation Professor of Geochemistry
Subject:  The geologic record of asteroid collisions and comet showers from cosmic dust 3He in marine sediments

Friday, May 3rd 2019
11:00 am:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: Samuel Giuliani, NSCL/FRIB Laboratory, Michigan State University
Subject: r process, kilonova and nucleosynthesis of superheavy elements: The role of fission

The rapid neutron capture process (r process) is responsible for the production of half of the elements heavier than iron that we observe in the Universe. The quest to identify its actual astrophysical site is still ongoing, but there are strong indications, including the recent observation of the GW170817 electromagnetic counterpart, that make neutron star mergers (NSM) a likely candidate. Reliable estimates of nucleosynthesis yields on NSM require an accurate description of the relevant nuclear physics inputs including nuclear masses, neutron capture rates, β- and α-decay rates and, for fissioning nuclei, fission rates and fission fragments distributions. Several of these quantities can be computed from a consistent theoretical framework using the energy density functional (EDF) approach.
In this talk I will revise how uncertainties in the nuclear physics properties of neutron-rich nuclei impact nucleosynthesis calculations, with a focus in the fission properties of (super)heavy nuclei. I will present a new set of fission rates obtained from microscopic nuclear many-body calculations, which are used as a nuclear input in r-process nucleosynthesis calculations in NSM. The possible formation of superheavy elements during the r-process nucleosynthesis as well as the impact on kilonova light curve, a quasithermal transient powered by freshly synthesized r-process nuclei, will be discussed. Finally, I will introduce recent developments in the estimation of fission yields and the possible extension to r-process nuclei.

12:20 pm:
Speaker: Saumitran Kastirurangan
Subject: Effect of disorder on boundary modes in nodal topological materials
12:30 pm:
Speaker: Sergei Dubovsky (NYU)
2:30 pm:
There will be no colloquium this week

Tuesday, May 7th 2019
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Prof. Mark Engebretson
Subject: MMS, Van Allen Probes, GOES 13, and Ground Based Magnetometer Observations of EMIC Wave Events Before, During, and After a Modest Interplanetary Shock
Speaker: Stefano Gonella and Bojan Guzina
Subject: What Lies Beneath: inverse scattering with sparse data (Guzina), and Learning the Sparse Code of Solids with Anomalies: A Model-Agnostic Approach to Wave-Based Diagnostics (Gonella)

Guzina: Waveform tomography and in particular inverse obstacle scattering are essential to a broad spectrum of scientific and technological disciplines, including sonar and radar imaging, geophysics, oceanography, optics, medical diagnosis, and non-destructive material testing. In general, any relationship between the wavefield scattered by an obstacle and its geometry (or physical characteristics) is nonlinear, which invites two overt solution strategies: (i) linearization via e.g. Born approximation and ray theory, or (ii) pursuit of the nonlinear minimization approach. Over the past two decades, however, a number of sampling methods have emerged that both consider the nonlinear nature of the inverse scattering problem and dispense with iterations. Commonly, these techniques deploy an indicator functional that varies with spatial coordinates of the trial i.e. sampling point, and projects the sensory data (namely observations of the scattered field) onto a functional space reflecting the ‘baseline’ wave motion in a background domain. This indicator functional, designed to reach extreme values when the sampling point strikes the anomaly, can be formulated from either a mathematical or a physical standpoint. An example of the latter methodology is perhaps best exemplified via the topological sensitivity (TS) approach. This talk will cover the idea and experimental validation of the TS methodology in the context of acoustic and elastic waves, including a recent backing of the approach within the framework of catastrophe theory.

Gonella: In this work we illustrate an approach to structural and materials diagnostics revolving around the mechanistic reinterpretation of concepts and methods originated in the fields of signal and image processing and machine learning. Anomalies and defects manifest in the dynamic response of a solid medium as a collection of salient and spatially localized events, which are reflected in the data structure of the response in the form of a set of behaviorally or topologically sparse features. We introduce a model-agnostic and baseline-free methodology that requires virtually no a priori knowledge of the medium’s material properties and forsakes the need for any knowledge of the system's behavior in its pristine state. This agnostic attribute makes the methodology powerful in dealing with media with heterogeneous or unknown property distribution, for which a material model is unsuitable or unreliable. The method revolves around the construction of sparse representations of the dynamic response, which are obtained by learning instructive dictionaries that form a suitable basis for the response data. The resulting sparse coding problem is recast as a modified dictionary-learning task with additional sparsity constraints enforced on the atoms of the dictionaries, which provides them with a prescribed spatial topology designed to unveil potential anomalous regions in the physical domain. The method is validated using synthetically generated data as well as experimental data acquired using a scanning laser Doppler vibrometer.

Faculty Host: Vuk Mandic

Wednesday, May 8th 2019
Speaker: Turab Lookman
Subject:  Vortex structures in ferroelectric nanoparticles

There has been much interest in topological defects of spontaneous polarization as templates for unique physical phenomena and in the design of electronic devices. Experimental investigations of the complex topologies of polarization have been limited to surface phenomena, which has restricted the probing of the dynamic volumetric domain morphology in operando. I will discuss the behavior of three-dimensional vortices formed due to competing interactions involving ferroelectric domains observed by Bragg coherent diffractive imaging. I will show results for a single BaTiO3 nanoparticle of size ~100 nm in a composite polymer/ferroelectric capacitor, and discuss the structural phase transitions under the influence of an external electric field, including a mobile vortex core exhibiting a reversible hysteretic transformation path and changes in toroidal moment. Results and extensions to Barium Hexaferrite, as well as some recent results on observations of skyrmions in YIG, will be pointed out. Time permitting, I will also discuss the observation of very large magnetostrictive coefficients in nanowires.

Faculty Host: Martin Greven

Thursday, May 9th 2019
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: David Weinberg, The Ohio State University
Subject: Decoding Chemical Evolution and Nucleosynthesis

I will discuss insights from analytic and numerical models of
galactic chemical evolution and observations of Milky Way
elemental abundances from the SDSS APOGEE survey. Under
generic model assumptions, abundances and abundance ratios
approach an equilibrium in which element production from
nucleosynthesis is balanced by element depletion from star
formation and outflows. Reproducing solar abundances requires
outflows with mass-loading factors of 1-3, but one can evade
this conclusion by assuming low stellar yields or metal-enhanced
winds; the high observed deuterium abundance of the local ISM
argues against these alternatives and in favor of outflows.
Starbursts or other sudden transitions can produce temporary
boosts in alpha-to-iron ratios, and other surprising behavior
such as backward evolution of a stellar population from high
metallicity to low metallicity. APOGEE observations show
that the distributions of stars in (alpha,iron,age)-space change
steadily across the Milky Way disk. Given these distributions,
the behavior of other APOGEE abundance ratios can be explained
by changes in the ratio of core collapse to Type Ia supernova
enrichment. The separability of "multi-element cartography"
offers a route to empirically constraining supernova yields
in a way that is insensitive to uncertainties in other aspects
of chemical evolution.

Faculty Host: Evan Skillman

Friday, May 10th 2019
12:20 pm:
Speaker: Robert Sponsel
Subject: TBA

Monday, May 13th 2019
10:00 am:
Speaker: Mikhail I. Dyakonov, Labarotoire Charles Coulomb, Université Montpellier, CNRS, France
Subject: Spin Hall effect and related phenomena

The spin Hall effect (SHE) was predicted nearly half a century ago [1, 2]. Following the proposal in [3], the (inverse) SHE was experimentally observed for the first time in [4], without arousing much interest. The first experimental observations of the (direct) SHE were reported [5, 6] more than 30 years after the original prediction, causing great excitement and many theoretical and experimental studies of this phenomenon.
The spin current density is described by a tensor qij, where the first index corresponds to the direction of flow, and the second one - to the component of the spin that is flowing.
The spin-orbit interaction provides coupling between the spin and charge currents, so that a charge current in the z direction produces the xy component of the spin current, resulting in spin accumulation at the lateral surfaces of the sample (direct spin Hall effect). In turn, the xy component of the spin current induces the z component of the charge current resulting in the change of the sample resistance (inverse spin Hall effect).
Related phenomena are the spin Hall magnetoresistance [7, 8] and the effect of swapping spin currents, which was predicted theoretically [9] but so far not yet observed experimentally.

Faculty Host: Boris Shklovskii

Tuesday, May 14th 2019
1:00 pm:
Speaker: Mikhail I. Dyakonov, Labarotoire Charles Coulomb, Université Montpellier, CNRS, France
Subject: Will we ever have a quantum computer?

The state of a classical computer at a given moment is described by a sequence (↑↓↑↑↓...), where ↑ and ↓ represent bits of information – realized as the on and off states of individual transistors. The computation process consists in switching some transistors between their ↑ and ↓ states according to a prescribed program.
In quantum computing one replaces the classical two-state element by a quantum element with two basic states, called the quantum bit, or qubit. The simplest object of this kind is the electron spin, which can have only two possible projections on any axis: +ћ/2 or −ћ/2. For some chosen axis, we can again denote the two basic quantum states of the spin as ↑ and ↓.
However an arbitrary spin state is described by the wave function ψ = a↑ + b↓, where a and b are complex numbers, satisfying the condition |a|2 + |b|2 = 1. In contrast to the classical bit that can be only in one of the two states, ↑ or ↓, the qubit can be in a continuum of states defined by the quantum amplitudes a and b. The qubit is a continuous object.
With N qubits, there are 2N basic states of the type (↑↓↓↑↑↓↑↓...). Accordingly, the general state of a system with N qubits is described by 2N complex parameters restricted by the normalization condition only. So, while the state of the classical computer with N bits at any given moment coincides with one of its 2N possible discreet states, the state of a quantum computer with N qubits is defined by the values of 2N continuous variables, that we should be able to control.
Thus, basic quantum mechanics tells us that the hypothetical quantum computer is an analog machine whose state at any given moment is described by a very large number of continuous parameters. Note that for a toy quantum computer with only 300 qubits this number greatly exceeds the number of particles in the observable Universe!
An important issue is related to the energies of the ↑ and ↓ states. While the notion of energy is of primordial importance in all domains of physics, both classical and quantum, it is not in the vocabulary of QC theorists. They implicitly assume that the energies of all 2N states of an ensemble of qubits are exactly equal. Otherwise, the existence of an energy difference ∆E leads to oscillations of the quantum amplitudes with a frequency Ω = ∆E/ ћ, where ћ is the Planck constant, and this again is a basic fact of Quantum Mechanics. (For example, one of the popular candidates for a qubit, the electron spin, will make a precession around the direction of the Earth's magnetic field with a frequency ~ 1 MHz).
On the basis of these elementary facts, the obvious answer to the question in title is - NO!

Faculty Host: Boris Shklovskii

Wednesday, September 25th 2019
1:25 pm:
Speaker: Scott Crooker, Los Alamos National Lab
Subject: TBD
Faculty Host: Paul Crowell

Wednesday, October 16th 2019
7:00 pm:
14th Annual Misel Family Lecture in McNamara Alumni Center 
Speaker: Professor Charles M. Marcus, Niels Bohr Institute

Thursday, October 17th 2019
3:35 pm:
14th Annual Misel Colloquium in Tate Hall B50
Speaker: Professor Charles M. Marcus, Niels Bohr Institute

Wednesday, November 13th 2019
1:25 pm:
Speaker: Ana Maria Rey, University of Colorado - Boulder
Subject: TBD

Thursday, November 14th 2019
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Ana Maria Rey, University of Colorado - Boulder
Subject: TBD
Faculty Host: Rafael Fernandes

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