# semester, 2018

Monday, January 1st 2018
08:00 am:

Friday, January 5th 2018
Speaker: No colloquium this week.

Wednesday, January 10th 2018
12:00 pm:
Community Recognition Luncheon in Tate B50 lobby

QUESTIONS? Contact Julie at jjmurphy@umn.edu or 612-625-6928

Speaker:  Jaebak Kim, Korea University
Subject:  Search for CP violation using T-odd correlations in D0 → K+K−π+π− decay / The 3-dimensional level one track trigger for the Belle II experiment

We search for CP violation using T-odd correlation in the singly Cabbibo suppressed D0 -> K+K-pi+pi- decay at the KEKB asymmetric e+e- collider. The D+- particles are reconstructed to tag the D0 particles and a triple product using the momentum of the D0's daughter particles is calculated. Cuts and vetos are applied to the reconstructed sample. A two dimensional simultaneous fit using four sub-samples depending on the triple product and D0 flavor while using the invariant mass of D0 and the invariant mass difference between D+ and D0 particles as the two dimensions is performed. The T-odd correlation and systematics are calculated.

The next generation e+ e- collision experiment called Belle II will start colliding particles this year. It will search for new physics using high precision measurements which were not possible before. The precision will be achieved by using a high luminosity beam. Due to the luminosity of the beam, there must be an fast and efficient trigger system in order to record the physics relevant data. The Belle II level 1 trigger system is a combination of sub-trigger FPGA based systems, where the main triggers are the central drift chamber (CDC) trigger and electromagnetic calorimeter detector trigger (ECL) trigger. Between them the CDC trigger finds the momentum and vertex position of charged tracks. These precise information will then be used to determine whether the event has
interesting physics or not. If the event is determined to be physics relevant, the DAQ system will record the detector data to disk. The level 1 CDC trigger consists of 7 types of boards. They are the Frontend boards, Merger boards, TSF boards, 2D finder board, Event time finder board, 3D tracker boards, and Neural Network boards. Each board has a specific function that makes tracking charged track possible with high precision.

Friday, January 12th 2018
Speaker: No colloquium this week.

Sunday, January 14th 2018
10:00 am:
Physics Force in Northrop
Physics Force show for elementary students. The show is free but reservations are required.

Monday, January 15th 2018

Tuesday, January 16th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.

Wednesday, January 17th 2018
1:25 pm:
Speaker: Jeff Derby (Dept. of Chemical Engineering and Materials Science, U of M)
Subject: The synergy of modeling and novel experiments for melt crystal growth research

Our understanding of crystal growth fundamentals and processes are advanced when the synergy between mathematical models and novel experiments is exploited. We present recent examples of how modeling and experiments together have enabled the identification of fundamental mechanisms important during the growth of bulk crystals from the melt.

We first discuss how microgravity experiments, carried out via sounding rockets, motivated a reexamination of classical theories for foreign particle engulfment during crystal growth. Via the development and application of rigorous numerical models, we were able, for the first time in over a decade of research on this system, to quantitatively describe data on the engulfment of SiC (silicon carbide) particles during the growth of crystalline silicon. Moreover, model results identified previously unascertained mechanisms responsible for the behavior of this system and, via this insight, provided insight for analytical derivation of a new scaling law for the dependence of critical engulfment velocity on particle size.

We finish with an overview of exciting, new research that employs neutron imaging to directly “see,” in operando, the bulk growth of scintillator crystals during a gradient-freeze process. We argue that the synergies of “seeing” via both models and neutron imaging will improve our fundamental understanding and provide for a closed-loop approach for optimizing the growth of large, single crystals from the melt.

This research was supported in part by NASA NNX10AR70G, DOE/NNSA DE-NA0002514, DOE/NNSA/DNN R&D (LBNL subcontract AC0205CH11231); no official endorsement should be inferred.

Faculty Host: Paul Crowell
3:35 pm:
To be announced.

Thursday, January 18th 2018
10:10 am:
Biophysics Seminar in PAN 120
Speaker: John Yin, University of Wisconsin
Subject: Paths to biological polymers: an insight from virus infections and origins of life

(1) Given the genome of a virus and PubMed, how well could one predict the one-step growth of the virus? Decades of biochemical and biophysical studies on bacteriophage T7, incorporated into a chemical kinetic model for template-dependent processes of transcription, translation, and genome replication, as well as particle assembly and release, enabled simulation of one-step growth behavior that recapitulated the experimentally observed kinetics of phage growth. Extension of the model and experiments to study the effects of host-cell physiology on phage growth highlighted the host cellular protein synthesis machinery as a key limiting resource for phage growth.
(2) Given amino acid monomers, but no cells, no templates and no protein synthesis machinery, how might the monomers nevertheless form polymers? The synthesis of peptide bonds between amino acids is a condensation reaction that is generally disfavored in aqueous solutions. However, we have found that for appropriate initial conditions of pH and temperature, drying of amino acids can promote their condensation to form peptides.
So what is the common insight from (1) and (2)? The often neglected “nurture” part of “nature versus nurture” can be important. The kinetics of phage growth depends on the physiological state of its host cell, and the de novo synthesis of a polypeptide species critically depends on the acidity and temperature of its initial solution. In short, we are all products of our environments.

Faculty Host: J. Woods Halley
3:35 pm:
Speaker: Harvey Brown, Philosophy of Physics, University of Oxford
Subject: Quantum Bayesianism (QBism): the way to understand the quantum world

The recent philosophy of Quantum Bayesianism, or QBism, represents an attempt to solve the traditional puzzles in the foundations of quantum theory by denying the objective reality of the quantum state. Einstein had hoped to remove the spectre of nonlocality in the theory by also assigning an epistemic status to the quantum state, but his version of this doctrine was recently proved to be inconsistent with the predictions of quantum mechanics. In this talk, I present plausibility arguments, old and new, for the reality of the quantum state, and expose what I think are weaknesses in QBism as a philosophy of science. (The talk is based on this paper: http://philsci-archive.pitt.edu/12978/

Friday, January 19th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
To be announced.
12:20 pm:
Speaker: Evan Moen
Subject: Spin Transport in Superconducting Spin Valves
Speaker: No colloquium this week.
3:35 pm:
Speaker: Harvey Brown, Philosophy of Physics, University of Oxford
Subject: "How Einstein Came to Use the Action-Reaction Principle in Promoting his Theory of Gravity"
Refreshments served at 3:15 p.m.

Einstein regarded as one of the triumphs of his 1915 theory of gravity — the general theory of relativity — that it vindicated the action–reaction principle, while Newtonian mechanics as well as his 1905 special theory of relativity supposedly violated it. In this talk I examine why Einstein came to emphasise this position several years after the development of general relativity. Several key considerations are relevant to the story: the connection Einstein originally saw between Mach’s analysis of inertia and both the equivalence principle and the principle of general covariance, the waning of Mach’s influence owing to de Sitter’s 1917 results, and Einstein’s detailed correspondence with Moritz Schlick in 1920. (The talk is based on ‘Einstein, the reality of space, and the action-reaction principle’, H.R.B. and Dennis Lehmkuhl, in Einstein, Tagore and the Nature of Reality, Partha Ghose (ed.), Routledge, London and New York, 2016; pp. 9-36. arXiv:1306.4902v1.)

4:40 pm:
Speaker: Priscilla Cushman, University of Minnesota
Subject: SuperCDMS - searching for dark matter
4:40 pm:
Organizational Meeting. Time and place of seminar will resume to match class schedule next week.

Monday, January 22nd 2018
1:25 pm:
To be announced.

Tuesday, January 23rd 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
To be announced.
2:30 pm:
Speaker: Chun Shen, Brookhaven National Laboratory
Subject: Going with the flow— the nuclear phase diagram at the highest temperatures and densities

Nuclear matter has a complex phase structure, with a deconfined Quark-Gluon Plasma (QGP) expected to be present under conditions of extreme pressure and temperature. The hot QGP filled the universe about few microseconds after the Big Bang. This hot nuclear matter can be generated in the laboratory via the collision of heavy atomic nuclei at high energy. I will review recent theoretical progress in studying the transport properties the QGP at almost zero baryon density. The recent beam energy scan experiments at the Relativistic Heavy-Ion Collider (RHIC) offer a unique opportunity to study the nuclear phase diagram in a hot and baryon-rich environment. I will focus on the development of a comprehensive framework that is able to connect the fundamental theory of strong interactions with the RHIC experimental observations. This dynamical framework paves the way for quantitative characterization of the QGP and for locating the critical point in the nuclear phase diagram. These studies will advance our understanding of strongly interacting many-body systems and build interconnections with other areas of physics, including string theory, cosmology, and cold atomic gases.

Wednesday, January 24th 2018
1:30 pm:
Speaker: Fiona Burnell (University of Minnesota)
Subject: Signatures of gapless boundary modes in Kitaev spin liquids

Recent progress in synthesizing insulators with a new type of dominant spin-exchange interaction, known as the Kitaev interaction, has opened new possibilities for experimentally realizing spin liquid compounds. Among the distinctive features of these spin liquids is the possibility that they can harbour protected gapless boundary modes which carry spin but not charge. This possibility raises a challenge of how best to detect these chargeless boundary modes. I will discuss two possibilities — Raman scattering and the heat capacity — as well as what such measurements can reveal about the bulk phase.

Faculty Host: Paul Crowell
Speaker: Dr. Shilpi Jain. National Central University Taiwan.
Subject: Search for H-->Zgamma—>llgamma with the CMS detector
Note change of time and room from previous announcement.

Jain will talk about the search for a Higgs boson decaying into a Z boson and a photon. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 35.9 fb-1. Limits are set on the cross section of a standard model Higgs boson decaying to electron or muon pairs and a photon. The expected exclusion limits at 95% confidence level are between 9 and 4 times the standard model cross section in the mass range of 120 and 130 GeV.

Thursday, January 25th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Ryan Marshall, UMN
Subject: Rapid and scalable characterization of CRISPR technologies using a cell-free transcription-translation system (TXTL)

CRISPR-Cas systems offer versatile technologies for genome engineering, yet their implementation has been outpaced by ongoing discoveries of new Cas nucleases and anti-CRISPR proteins. We present the use of E. coli cell-free transcription-translation (TXTL) systems to vastly improve the speed and scalability of CRISPR characterization and validation. TXTL can express active CRISPR machinery from added plasmids and linear DNA, and TXTL can output quantitative dynamics of DNA cleavage and gene repression—all without protein purification or live cells. We use TXTL to measure the dynamics of DNA cleavage and gene repression for single and multi-effector CRISPR nucleases, predict gene repression strength in E. coli, determine the specificities of diverse anti-CRISPR proteins, develop a fast and scalable screen for protospacer-adjacent motifs, and show that dCas9 bound to a protospacer can be displaced. These examples underscore how TXTL can facilitate the characterization and application of CRISPR technologies across their many uses.

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

Friday, January 26th 2018
08:00 am:
Untitled in Physics
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be a special nuclear physics seminar on Tuesday this week.
12:20 pm:
Speaker: Nicholas Lewellyn
Subject: Magnetic Field tuned superconductor-metal transition in InOx

Quantum phase transitions are an interesting topic in condensed matter physics that has been studied extensively. One example of a quantum phase transition is the superconductor-insulator transition in InOx. These transitions are typically studied using scaling analysis. In the case of a field tuned transition this starts with measuring various resistance versus field isotherms. The field at which the isotherms cross is taken as the critical field and used in the scaling analysis and to find the critical exponents. However, in some systems, such as one of our InOx thin films, there is not a single crossing, instead the crossing is smeared out resulting in a temperature dependent critical field and critical exponents. Detailed transport measurements of the superconductor-metal transition in this sample suggest that this temperature dependent behavior may be the result of a quantum Griffiths singularity. Similar behavior how been observed by other groups in different materials that also undergo superconductor-metal transitions.

Speaker: Jorn Kersten (Bergen U., Norway)
Subject: Late Kinetic Decoupling and Self-Interacting Dark Matter

The cosmological LambdaCDM standard model faces some problems related to the formation of structures at relatively small scales, most notably the missing-satellites problem, the cusp-core problem, the too-big-to-fail problem, and the diversity problem. I will advertise late kinetic decoupling of dark matter as a mechanism to address the missing satellites problem. Afterwards, I will describe a model involving self-interacting dark matter and sterile neutrinos that can tackle all four small-scale problems.

Speaker: No colloquium this week.
3:35 pm:
Speaker: Nancy Tomes, Department of History, Stony Brook University
Subject: "’Recovery’ as Concept, Model, and Movement in the Mental Health Field: the Challenge of Writing a ‘History of the Present’"
Refreshments served at 3:15 p.m.

Since the 1980s, the recovery concept has become central to efforts to empower people with severe and persistent mental illness. Advocates of the recovery model stress the importance of non-medical measures, such as supported employment, supported housing, strong community networks and perhaps most importantly, the support and leadership of other people with lived experience of mental illness. My talk will explore both the history and the historiography of the recovery model in the mental health field. I will discuss how the approaches that emerged in the 1970s and 1980s differed from previous attempts at “after care” for ex-mental patients, and look at their overlap with contemporary developments in addiction treatment and the disability rights movement. Finally, I will discuss criticisms of the recovery movement and its place in late 20th c. “reforms” of the welfare state as an example of how historical scholarship intersects with contemporary advocacy concerns and policy issues.

3:35 pm:
Speaker: Miranda Straub

This talk will present the initial analysis of 25 physics instructor interviews from post-secondary institutions around the state of Minnesota. The interviews focused on problem solving, and this talk will highlight beliefs about homework. Specifically, what do instructors think students should do and learn while they are doing homework.

4:40 pm:
Speaker: Ke Wang, University of Minnesota
Subject: Quantum Control in 2D Van der Waals Nanostructures

Monday, January 29th 2018
12:15 pm:
There will be no seminar this week.
3:30 pm:
FTPI Special Seminar in Tate 301-20
Speaker: Maxim Pospelov
Subject: "Widening the net in search for New Physics"
Candidate for FTPI Faculty Position

Following spectacular confirmation of the Standard Model at the LHC, the emphasis of particle physics shifts towards searches for physics beyond Standard Model. The clues for new physics may be hidden in cosmological data that suggest the dominance of dark matter and dark energy throughout the Universe. I will describe some recent aspects of widening the search for new physics focussing on light dark matter and in general on light weakly coupled states. I will introduce constraints on dark matter - electron scattering that result from a new phenomenon, the reflection of dark matter from the solar interior. I will also argue that besides conventional probes of light weakly coupled states, further insight can be gained by involving precision AMO tools, and describe some recent experimental activity in this direction.

Faculty Host: Keith Olive

Tuesday, January 30th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Oleksiy Agapitov, Space Sciences Laboratory, University of California, Berkeley
Subject: Nonlinear wave-particle and wave-wave interactions in the outer radiation belt: physical mechanisms and observational effects
1:00 pm:
FTPI Special Seminar in Tate 201-20
Speaker: Maxim Pospelov
Subject: "Light Z' coupled to poorly conserved currents"
Candidate for FTPI Faculty Position
Faculty Host: Keith Olive
3:30 pm:
Speaker: Damjan Pelc, University of Minnesota
Subject: New ways to learn about quantum materials
Refreshments will be served at the meeting so don't forget to bring your favorite mug.

I will discuss two unusual experimental techniques currently being developed for the study of quantum materials: nonlinear magnetic response and uniaxial pressure. They can be used to detect and modify the fundamental symmetries of materials, with great potential for new insights. In particular, I will examine the symmetry properties of nonlinear magnetic susceptibility, with applications in the study of chiral superconductors. Furthermore, I will present a novel approach to uniaxial pressure experiments, which can easily be combined with various other techniques to investigate the effects of broken structural symmetries.

Wednesday, January 31st 2018
1:30 pm:
Speaker: Sergey Frolov, University of Pittsburgh
Subject: Quantum dot chains as emulators of topological superconductors

Tunneling spectroscopy measurements on one-dimensional superconducting hybrid materials have revealed signatures of Majorana fermions which are the edge states of a bulk topological superconducting phase. We couple strong spin-orbit semiconductor InSb nanowires to conventional superconductors (NbTiN, Al) to obtain additional signatures of Majorana fermions and to explore the magnetic-field driven topological phase transition. Specifically, we map out the phase diagram of the topological phase in the space of Zeeman energy and chemical potential, and investigate the apparent closing and re-opening of the superconducting gap. We investigate how the topological superconducting phase would manifest in finite size systems, by electrostatically splitting the wire into segments of varied length. By chaining up several segments of a nanowire, we are realizing a quantum simulator of the Kitaev chain with tunable on-site energies and couplings between the sites, a step towards quantum simulation with semiconductor nanostructures.

3:35 pm:
To be announced.

Thursday, February 1st 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Joseph Muretta, University of Minnesota, Biochemistry, Molecular Biology and Biophysics
Subject: Adventures in Biophysics: Lysine Acetylation Tunes Mechanochemical Coupling and Force Output in a Mitotic Kinesin
Speaker: Claudia Scarlata
3:35 pm:
Speaker: Mark Bell, University of Minnesota
Subject: Nuclear Weapons and International Politics Today

Nuclear weapons are back in the news. This talk provides an overview of the most important and pressing current issues relating to nuclear weapons and international politics, including ongoing US-North Korea tensions, US nuclear modernization and the US Nuclear Posture Review, the extent of presidential authority over nuclear weapons, the risk of nuclear proliferation by U.S. allies and adversaries, and the recent nuclear ban treaty. The talk places these current issues within a broader historical context and discusses the extent to which today's nuclear concerns represent continuity or change from previous eras.

Faculty Host: Robert Lysak

Friday, February 2nd 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be no seminar this week.
12:20 pm:
Speaker:  Zedong Yang, University of Minnesota
Subject: Towards spin injection into semiconductor nanowires

InSb nanowires have been established as a versatile materials platform for realizing Majorana bound states and for investigating spin-orbital interaction (SOI) and large effective g-factor. By coupling InSb nanowires to ferromagnetic (FM) contacts, a spin-polarized current can be injected into the nanowires and subsequently controlled by electric fields. We will report on our progress fabricating nanowire devices with FM electrodes in local spin-valve geometry, as well as discussing our low-temperature transport experiments on these devices.

Speaker: Liliana Velasco-Sevilla (Bergen U., Norway)
Subject: How multi-Higgs Physics Could Uncover the Nature of Flavour
1:35 pm:
There is no seminar this week.
Speaker: No colloquium this week.
3:35 pm:
Speaker: Marc Swackhamer, School of Architecture, University of Minnesota
Subject: "Hypernatural: Architecture's New Relationship with Nature" - MCPS Annual Science Studies Symposium
Refreshments served at 3:15 p.m.

Recent decades have witnessed the increasing popularity of nature-focused movements in architecture, such as sustainability, biophilia, biomimicry, biodesign, and emergent design. These movements are dramatically altering the relationship between the designed environment and the natural world, and although overlaps exist, there is no common discourse that unites these areas of study. A holistic framework is therefore needed to address these disparate areas of inquiry, the full spectrum of their operations, and their common goals and methodologies. This talk will address the ways in which architectural designers increasingly work directly with natural processes—rather than against them—in order to amplify, extend, or exceed natural capacities.

4:40 pm:
Speaker: Jochen Mueller, University of Minnesota
Subject: Physics of the cell: From viral assembly to fluctuating membranes

Monday, February 5th 2018
Speaker: Jeff Pedelty, NASA
Subject: Jeff will share his diverse experiences while working for NASA and its industrial partners.

Jeff earned a B.S. in physics from the Iowa State University in 1981 and a Ph.D. in astrophysics from the University of Minnesota in 1988. His thesis combined observational radio astronomy with Professor Rudnick and computational fluid dynamics with Professor Woodward. Since leaving Minnesota he has worked for NASA’s Goddard Space Flight Center in Greenbelt, MD. He supported the Nobel-winning Cosmic Background Explorer (COBE), the Earth science missions Landsat 7, 8, and 9, and the Joint Polar Satellite System (JPSS-1) weather satellite. He also worked in the areas of high performance computing, signal and image processing, astrobiology, and remote sensing science. For the past 10 years he has worked for the Landsat Project onsite at Ball Aerospace in Boulder, CO and at Orbital ATK in Gilbert, AZ.

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

Tuesday, February 6th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Dr. Ricky Egeland, High Altitude Observatory, National Center for Atmospheric Research.
Subject: A Critical Rossby Number for Sun-Like Variability

Despite centuries of observation and decades of theoretical work, the ~11 year solar magnetic sunspot cycle remains one of the longest-standing unsolved problems in astrophysics. Additional insights can be made using synoptic observations of proxies for magnetism in other stars, where the varied stellar properties set the conditions for separate "dynamo experiments." We examine the decadal-scale variability in Ca II H & K emission of the Sun and a set of 26 solar analog stars within ~5% of the solar effective temperature but with varied mean rotation. Using a quantitative metric for determining cycle quality, we find that cycles of the highest quality—like the Sun's—occur in the stars with slower rotation and lower mean activity. Reexamining the results of a larger set of ~100 stars from the Baliunas et al. 1995 study of Mount Wilson H & K emission, we find again that the highest quality cycles occur for low activity and high Rossby number, the ratio of the rotation period to the convective turnover time. Guided by these observations, we propose the hypothesis that Sun-like variability—either a clean, monoperiodic cycle or flat activity analogous to the Maunder Minimum—occurs in G- and K- type main-sequence stars if and only if the Noyes et al. 1984 semi-empirical Rossby number is larger than 1.5, or equivalently if the star is on the low-activity side of the Vaughan-Preston gap. These results demonstrate the critical role of the Rossby number in determining the behavior of stellar dynamos.

1:30 pm:
Speaker: Rafael Fernandes, University of Minnesota
Subject: TBD
2:30 pm:
Subject:  Multimessenger astrophysics with numerical relativity
Candidate for the Nucear Theory Assistant Professor position

How are neutron stars formed and what is inside them? What is the
engine powering short gamma-ray bursts? What is the astrophysical site
of production of heavy elements? Multimessenger observations of
compact binary coalescence and core-collapse supernovae might provide
us with the key to answer these and other important open questions in
theoretical astrophysics. However, multimessenger astronomy also poses
new challenges to the theorists who need to develop models for the
joint interpretation of all data channels. In this talk, I will
present recent theoretical results. I will review the landmark
multimessenger observation of merging neutron stars, and I will
discuss its interpretation and implication in the light of results
from first-principles simulations. Finally, I will discuss future
challenges and prospective for this nascent field.

Wednesday, February 7th 2018
1:30 pm:
Speaker: Cristian Batista, University of Tennessee
Subject: Pairing from strong repulsion in the triangular lattice Hubbard model

The generation of an effective attraction between electrons out of the bare Coulomb repulsion is a long sought-after goal of the condensed matter community. In this talk I will introduce a pairing mechanism between holes in the dilute limit of doped frustrated Mott insulators. We will see that magnons provide a strong glue in the infinitely repulsive limit of the triangular lattice Hubbard model. The strongly attractive hole-magnon interaction is a manifestation of a “counter-Nagaoka” theorem: the single-hole kinetic energy is minimized for an antiferromagnetically ordered state. We will demonstrate that the resulting hole-magnon attraction is strong enough to bind a second hole and to form a hole-hole-magnon three-body bound state. Remarkably, the binding energy of this “composite Cooper pair” is rather strong, while its effective mass still has a moderate value, giving rise to relatively high transition temperature for superconductivity in the dilute limit. I will discuss a few interesting consequences of this new mechanism for unconventional superconductivity.

Work done in collaboration with Shangshun Zhang (University of Tennessee) and Wei Zhu (Los Alamos National Laboratory).

Faculty Host: Natalia Perkins
Subject: Latest Results on Higgs to Diphotons from CMS

The most-recent results on Higgs to diphotons measurements from CMS will be reviewed. (Speaker is a candidate for a postdoctoral research position and will be presenting by video)

Thursday, February 8th 2018
10:10 am:
Biophysics Seminar in 120 PAN
No Seminar This Week
Speaker: Liliya Williams and Stou Sandalski
3:35 pm:
Speaker: Cristian Batista, University of Tennessee
Subject: Skyrmions and Vortices in Magnetic Systems

The history of magnetism dates back to earlier than 600 b.c., but it is only in the twentieth
century that scientists have begun to understand it, and develop technologies based on this
understanding. The new experimental techniques that were developed over twentieth century
allowed physicists to discover new forms of magnetism that they called “antiferromagnets”.
Unlike ferromagnets, the magnetic moments of antiferromagnets point along different directions
in such a way that the magnetic unit cell has no net magnetic moment. Typical configurations of
antiferromagnets are spiral orderings arising from competing exchange interactions or from the
Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction between magnetic moments embedded
in metallic environments.
The new century started with the observation of a new generation of antiferromagnets
comprising more exotic magnetic textures, such as skyrmion and vortex crystals [1-3]. These
textures were unveiled thanks to the enormous progress made in real and reciprocal space
visualization techniques. We will discuss a few attractive properties of these novel phases and
the simple principles that should guide the experimental search. For instance, we will see that an
external magnetic field can induce a skyrmion crystal phase in hexagonal lattices (lattices with
six equivalent orientations for the spiral ordering) with easy-axis anisotropy [4-10]. Moreover,
we will see that magnetic skyrmions behave as mesoscale particles, which can order in different
three-dimensional structures, such as face centered tetragonal and hexagonal closed packed
crystals [10].
References
[1] U. Rößler, A. Bogdanov, and C. Pfleiderer, Nature 442, 797 (2006).
[2] A. N. Bogdanov and D. A. Yablonskii, Sov. Phys. JETP 68, 101 (1989).
[3] A. Bogdanov and A. Hubert, Journal of Magnetism and Magnetic Materials 138, 255 (1994).
[4] S. Hayami, S.-Z. Lin, and C. D. Batista, Phys. Rev. B 93, 184413 (2016).
[5] A. O. Leonov and M. Mostovoy, Nature Communications 6, 8275 (2015).
[6] Shi- Zeng Lin, Satoru Hayami and C. D. Batista, Phys. Rev. Lett. 116, 187202 (2016).
[7] C. D. Batista, S-Z. Lin, S. Hayami and Y. Kamiya, Reports on Progress in Physics, Volume 79, 8
(2016).
[9] Satoru Hayami, Shi-Zeng Lin, Yoshitomo Kamiya, and Cristian D. Batista, Phys. Rev. B 94, 174420.
[10] Shi-Zeng Lin and C. D. Batista, arXiv:1707.05818v1.

Faculty Host: Natalia Perkins

Friday, February 9th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be a special nuclear physics seminar on Tuesday this week.
12:20 pm:
Speaker: Xuzhe Ying, University of Minnesota
Subject: Topological Metals

I will discuss how to obtain a gapless phase from a topological gapped phase by breaking both time reversal and inversion symmetry. The specific model would be 2D p+ip chiral superconductor. 2D chiral superconductor belongs to symmetry class D with particle-hole symmetry and could support chiral Majorana. A supercurrent could break inversion symmetry and make system gapless. I'm going to discuss that particle-hole symmetry guarantees that there is a metallic phase which is distinct from trivial metal.

Speaker: Robert Lasenby (Perimeter)
Subject: Searching for Weakly Coupled New Particles with Stellar Cooling

Many theories of beyond Standard Model physics include new light, weakly-coupled particles, which can be challenging to search for experimentally. The high densities and temperatures in stellar cores allow them to produce such particles in large numbers, while the large volume to surface area ratio of stars enhances the relative effects of such production on stellar energy transfer and cooling. This makes stellar observations into a sensitive probe of new particles. I’ll describe how the plasma environment in stellar cores can parametrically alter the rates for these processes, and how this can significantly change the constraints and discovery potential for some new particle candidates. I’ll also discuss some other situations where in-medium effects are important in the search for weakly-coupled new physics.

Speaker: Terry Jones, University of Minnesota
Subject: Interstellar Polarization

This talk will start with a bit of retrospective on my career in astronomy, after which I will focus on the topic of interstellar polarization. I will concentrate on work done here at the University of Minnesota, up to current work using MMTPol on the MMT and HAWC+ on SOFIA. The primary science goal of this work is to study the magnetic field geometry in all phases of the interstellar medium, and determine what limitations there are to that effort. Lastly, I will describe some future trends.

3:35 pm:
Speaker: Jacqueline Feke, Department of Philosophy, University of Waterloo
Subject: "Ptolemy's Ethics"
Refreshments served at 3:15 p.m.

Why did Ptolemy devote his time to the mathematical sciences, especially astronomy? The answer lies in his brief ethical statement in the first chapter of the Almagest. Coopting virtue ethics for the mathematician, Ptolemy argues that the best life is the one devoted to mathematics, where the mathematician configures his soul in accordance with the good order in the heavens. In this paper, I analyze this ethical statement and argue that to understand why and how astronomical objects serve as ethical exemplars in Ptolemy’s philosophy we must look to his Harmonics. It is because musical pitches, heavenly bodies, and human souls are all characterized by harmonic ratios that the study of either harmonics or astronomy can lead to the good life.

3:35 pm:
Speaker: Kaylee Ganser
Subject: The Effect of Active Learning Classes on Introductory Physics Student Performance at UMN-Duluth

In order to determine the effect the new active learning classroom had on academic gains for introductory physics students at UMN-Duluth, we analyzed three data sets: the scores from a diagnostic test given at both the beginning and end of the semester (the Force Concept Inventory) and the scores from a common problem on the final exam (scored using a common checklist) for Spring 2016, and the FCI scores for Fall 2016. For the Spring 2016 semester, we
compared 3 Active Learning classes with a lecture group as a control, and for Fall 2016, all sections were Active Learning. For Spring 2016, we found that, for sufficiently ‘Active Learning’ style based teaching methods, the active learning classroom improved student scores compared to previous data, but the lecture section failed as a control due to various factors. For the Fall 2016 classes, the academic gains were less than both of Spring 2016’s data sets and past data, which indicates that additional criteria beyond simply moving into an Active Learning style classroom may be necessary to improve student scores or that students are learning skills not testable by the FCI. Academic gains made by women and racial minority students are suggestive of an improvement in active learning classes, but more data is needed to determine the true extent of this effect.

4:40 pm:
Speaker: Vincent Noireaux, University of Minnesota
Subject: DNA programmed dynamical systems outside cells: from gene circuits to self-assembly

Monday, February 12th 2018
12:15 pm:
Speaker: Lawrence Rudnick, UMN
Subject: The Stormy Life of Galaxy Clusters

This is a modified version of my plenary talk from the recent AAS Meeting. Regular cosmo seminar attendees will have seen some of this before, but this talk puts things into a larger, and hopefully useful, context.

Galaxy clusters, the largest gravitationally bound structures, hold the full history of their baryonic evolution, serve as important cosmological tools and allow us to probe unique physical regimes in their diffuse plasmas. With characteristic dynamical timescales of 107-109 years, these diffuse thermal and relativistic media continue to evolve, as dark matter drives major mergers and more gentle continuing accretion. The history of this assembly is encoded in the plasmas, and a wide range of observational and theoretical investigations are aimed at decoding their signatures. X-ray temperature and density variations, low Mach number shocks, and "cold front" discontinuities all illuminate clusters' continued evolution. Radio structures and spectra are passive indicators of merger shocks, while radio galaxy distortions reveal the complex motions in the intracluster medium. Deep in cluster cores, AGNs associated with brightest cluster galaxies provide ongoing energy, and perhaps even stabilize the intracluster medium. In this talk, we will recount this evolving picture of the stormy ICM, and suggest areas of likely advance in the coming years.

3:30 pm:
Speaker: Katherine Freese
Subject: The Dark Matter in the Universe
Candidate for FTPI Faculty Position

“What is the Universe made of?” This question is the longest outstanding problem in all of modern physics, and it is one of the most important research topics in cosmology and particle physics today. The bulk of the mass in the Universe is thought to consist of a new kind of dark matter particle, and the hunt for its discovery in on. I'll start by discussing the evidence for the existence of dark matter in galaxies, and then show how it fits into a big picture of the Universe containing 5% atoms, 25% dark matter, and 70% dark energy. Neutrinos only constitute ½% of the content of the Universe, but much can be learned about neutrino properties from cosmological data. Leading candidates for the dark matter are Weakly Interacting Massive Particles (WIMPs), axions, and sterile neutrinos. WIMPs are a generic class of particles that are electrically neutral and do not participate in strong interactions, yet have weak-scale interactions with ordinary matter. There are multiple approaches to experimental searches for WIMPS: at the Large Hadron Collider at CERN in Geneva; in underground laboratory experiments; with astrophysical searches for dark matter annihilation products, and upcoming searches with the James Webb Space Telescope for Dark Stars, early stars powered by WIMP annihilation. Current results are puzzling and the hints of detection will be tested soon. At the end of the talk I'll briefly turn to dark energy and its effect on the fate of the Universe.

Faculty Host: Keith Olive

Tuesday, February 13th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.
1:00 pm:
FTPI Special Seminar in Tate 201-20
Speaker: Katherine Freese
Subject:  Inflationary Cosmology: Theoretical Developments and Status in light of Cosmic Microwave Background Data
Candidate for FTPI Faculty Position
Faculty Host: Keith Olive
3:30 pm:
Speaker: Maria Navarro Gastiasoro, University of Minnesota
Subject: "Superconductivity in Strontium Titanate"

Wednesday, February 14th 2018
1:25 pm:
Speaker: Damjan Pelc (University of Minnesota)
Subject: Inhomogeneous charge localization in the cuprates

I will discuss new experimental results and insights into the physics of cuprate high-temperature superconductors, providing an overarching framework for understanding these materials.
Motivated by transport measurements, I will consider an inhomogeneous Mott-like (de)localization model wherein exactly one hole per copper-oxygen unit is gradually delocalized with increasing doping and temperature. The model comprehensively captures pivotal unconventional experimental results, including the temperature and doping dependence of the pseudogap phenomenon, the strange-metal linear temperature dependence of the planar resistivity, and the doping dependence of the superfluid density. The simple model greatly demystifies the cuprate phase diagram, and points to a local superconducting pairing mechanism involving the (de)localized hole. The spatial inhomogeneity of the localization gap is thus expected to cause a distribution of superconducting gaps as well, leading to superconducting percolation. Accordingly, for several representative cuprates the superconducting diamagnetism, nonlinear conductivity, and paraconductivity exhibit an unusual temperature dependence above Tc that is captured by a simple percolation model. The results show that that intrinsic, universal gap inhomogeneity is highly relevant to understanding the properties of the cuprates.

Faculty Host: Paul Crowell
To be announced.

Thursday, February 15th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Jasmine Foo, School of Mathematics, University of Minnesota
Subject: Impact of the tumor microenvironment on drug resistance in cancer

Despite the effectiveness of many therapies in reducing tumor burden during the initial phase of treatment, the emergence of drug resistance remains a primary obstacle in cancer treatment. Tumors are comprised of highly heterogeneous, rapidly evolving cell populations whose dynamics can be modeled using evolutionary theory. In this talk I will describe some mathematical models of the evolutionary processes driving drug resistance in cancer, and demonstrate how these models can be used to provide clinical insights. These models will be applied to study the impact of dosing schedules and the tumor microenvironment on the emergence of drug resistance in lung cancer.

3:35 pm:
Speaker: Mark Saffman (University of Wisconsin)
Subject: Quantum computing with simple and complex atoms
Refreshments in atrium after the Colloquium.

Quantum computing is a few decades old and is currently an area where there is great excitement, and rapid developments. A handful of distinct approaches have shown the capability of on demand generation of entanglement and execution of basic quantum algorithms.

One of the daunting challenges in developing a fault tolerant quantum computer is the need for a very large number of qubits. Neutral atoms are one of the most promising approaches for meeting this challenge. I will give a snapshot of the current status of quantum computing in general and atomic quantum computing in particular. The atomic physics underlying our ability to control neutral atom qubits will be described, and I will show how one of the most complicated atoms in the periodic table may lead to some simple solutions to hard problems.

Faculty Host: Paul Crowell

Friday, February 16th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be no seminar this week.
12:20 pm:
Speaker: Jianlong Fu
Subject: Majorana representations of spin and the Kitaev honeycomb model

Quantum spin liquid has been studied intensively in recent years. Among various types of spin liquid, the Kitaev model is unique because it is exactly solvable. Kitaev’s original solution is based on Majorana representation of spin. In this talk, I will discuss three types of Majorana representation of spin and argue that they can be linked together by Dirac spinor representation of SO(4) group. Then, I will discuss an alternative solution of the Kitaev model using another Majorana representation and talk about aspects of the solution.

Speaker: No seminar this week
Speaker: Evan Skillman, MIfA
Subject: The Resolved Stellar Populations JWST Early Release Science Program

Our JWST ERS program will obtain deep multi-band NIRCam and NIRISS imaging of three resolved stellar systems within 1 Mpc. We will use this broad science program to optimize observational setups and to develop data reduction techniques that will be common to JWST studies of resolved stellar populations. We will combine our expertise in HST resolved star studies with these observations to design, test, and release point spread function (PSF) fitting software specific to JWST. PSF photometry is at the heart of resolved stellar populations studies, but is not part of the standard JWST reduction pipeline. Our program will establish JWST-optimized methodologies in six scientific areas: star formation histories, measurement of the sub-Solar mass stellar IMF, extinction maps, evolved stars, proper motions, and globular clusters, all of which will be common pursuits for JWST in the local Universe. Our observations will be of high archival value (e.g., for calibrating stellar evolution models, measuring properties of variable stars, and searching for metal-poor stars) and will provide blueprints for the community to efficiently reduce and analyze JWST observations of resolved stellar populations.

3:35 pm:
Speaker: Cynthia Connolly, School of Nursing, University of Pennsylvania
Subject: "A 'Big Business Built for Little Customers:' Children and the Flavored Aspirin Market in the United States, 1948–1973"
Refreshments served at 3:15 p.m.

By the early postwar era, new children’s consumer goods such as sweetened cereals, toys, games, and books flooded the market. In September, 1947, the bright orange-colored St. Joseph Aspirin for Children joined them amid a wave of creative marketing for what became known as candy aspirin. An immediate success, flavored low dose aspirin reshaped medical, nursing, and parental responses to pediatric fever and pain. Unfortunately, however, its popularity with children resulted in an unintended consequence—a 500% increase in aspirin poison rates within a few years. While pediatricians and public health activists argued for warning labels and reconfigured bottles that made it harder for children to access the pills, the aspirin industry went on the offense, using tactics similar to those of the cigarette industry— challenge the problem’s existence; the data underpinning the science; deflect blame onto parents; and mount a public relations campaign aimed at confusing the public. This paper analyzes a complicated set of negotiations at the junction of science, commerce, and childhood. In an era rife with child protection rhetoric, debates surrounding children’s aspirin in the years between 1948 and 1973 reveal the competition among stakeholders to “speak” for children, the many negotiations regarding how to determine children’s “best interests,” and what can happen when recommendations for children’s well-being challenge the economic well-being of major corporations.

3:35 pm:
To be announced.
4:40 pm:
Speaker: Paul Crowell, University of Minnesota
Subject: Spin Transport and Dynamics in Metals and Semiconductors

Monday, February 19th 2018
09:30 am:
Thesis Defense in Tate-301
Speaker: Kate Raach, University of Minnesota
Subject: Characterization, Optimization, and Operation of TES Bolometers for EBEX
Please note time of defense was incorrect in previous message.
12:15 pm:
Speaker: Marcelo Alvarez, UC Berkeley, Berkeley Center for Cosmological Physics
Subject:  The Bright Future of Reionization with 21 cm and CMB Observations

In the coming decade we will witness the completion of CMB and 21 cm experiments that promise to lift the veil on reionization. Up until now, the details of reionization have remained shrouded in mystery across the chasm of space and time that separates us from the billion years after the big bang in which it occured, more than 12 billion years ago and 30 billion light years away due to cosmic expansion. CMB observations probe the distribution of what we think was a complicated network of growing and overlapping ionized bubbles created by UV and X-ray ancient dwarf galaxies and newborn supermassive black holes, while 21 cm observations probe the neutral patches left behind. As such, these two types of observations provide complementary information about the first billion years. I will discuss the exciting new prospects for understanding reionization by analyzing upcoming 21 cm and CMB observations jointly, emphasizing how simulations can help us avoid the pitfalls associated with teasing out the faint signals from nearby foregrounds, instrumental noise, and systematics.

Faculty Host: Shaul Hanany
3:30 pm:
Speaker: Mithat Unsal
Subject: Decoding path integrals: Resurgence and mass gap
Candidate for FTPI Faculty Position

I will provide an introductory level overview of recent
applications of resurgent trans-series and Picard-Lefschetz theory to
quantum mechanics and quantum field theory.
Resurgence connects local perturbative data with global topological
structures. In quantum mechanical systems, this program provides a
constructive relation between different saddles. For example, in
certain cases it has been shown that all information around the
instanton saddle is encoded in perturbation theory around the
perturbative saddle. In quantum field theory, such as sigma-models
compactified on a circle, neutral bions provide a semi-classical
interpretation of the elusive IR-renormalon, and fractional kink
instantons lead to the non-perturbatively induced mass gap exactly of
order of the strong scale. I also describe the concept of hidden
topological angle, a phase associated with Lefschetz thimbles.
Hidden topological angle may provide destructive/constructive
interference effects between equally dominant saddles in the Lefschetz
thimble decomposition, providing resolution to some time standing
puzzles in non-perturbative analysis.

Faculty Host: Keith Olive

Tuesday, February 20th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Pat Meyers, University of Minnesota
Subject: Extremely low frequency electromagnetic waves and gravitational-wave detectors

The current generation of gravitational-wave (GW) detectors has already made phenomenal discoveries. One of the next frontiers of GW astrophysics is a measurement of the stochastic gravitational-wave background (SGWB). The SGWB is a superposition of many unresolvable stellar sources of GWs and potentially GWs from the earliest epochs of the Universe. Current searches for an SGWB rely on long cross-correlation measurements made with data from detectors separated by thousands of kilometers. The most likely source of correlated noise between detectors this far apart is extremely low frequency, persistent, electromagnetic waves like Schumann resonances. I'll discuss how these waves are produced, some recent measurements made using a global network of magnetometers, and how the waves can couple into GW detectors. Finally, I'll discuss development of methods to budget for and potentially subtract them from the GW data.

1:00 pm:
FTPI Special Seminar in Tate 201-20
Speaker: Mithat Unsal
Subject: Phase transitions, semi-classics and anomalies
Candidate for FTPI Faculty Position
Faculty Host: Keith Olive
2:30 pm:
Speaker:  Jorge Noronha, Universidade de Sao Paulo
Subject: Unveiling the secrets of nature's primordial liquid
Candidate for the Nucear Theory Assistant Professor position

Microseconds after the Big Bang, the Universe cooled into an exotic phase of matter. There the fundamental building blocks of Quantum Chromodynamics (QCD), known as quarks and gluons, were not confined inside the core of atomic nuclei. Tiny specks of this early Universe matter, called the Quark-Gluon Plasma (QGP), are now being copiously produced in heavy ion collisions at both RHIC and the LHC. These experiments provide overwhelming evidence that the QGP flows like a nearly frictionless strongly coupled liquid over distance scales not much larger than the size of a proton. Thus, the QGP formed in particle colliders is the hottest, smallest, densest, most perfect liquid known to humanity. Yet, the theoretical underpinnings behind the liquid-like behavior of QCD matter remain elusive.

In this talk I will present first principles calculations performed within string theory and relativistic kinetic theory that have shed new light on the emergence of hydrodynamic behavior in QCD and challenged the very foundations of fluid dynamics. New techniques to determine the real time, far-from-equilibrium dynamics of QCD in the large baryon density regime will also be discussed to lead current experimental efforts to discover critical phenomena in the fundamental theory of strong interactions.

Wednesday, February 21st 2018
1:25 pm:
Speaker: Erez Berg (U of Chicago)
Subject: Transport beyond the quasiparticle picture: a view from the large-N limit

In normal metals, the electron's mean free path is much larger than its wavelength, allowing a semiclassical treatment of transport. Conversely, whenever scattering is so strong that the mean free path becomes comparable to the electron's wavelength, the concept of a quasiparticle becomes ill defined, and a new theoretical framework is needed. I will introduce a family of lattice models for interacting electrons that can be solved exactly in the limit of a large number of interacting electron flavors and/or phonon modes. Depending on details, these models exhibit either "resistivity saturation" at high temperatures to a value of the order of the quantum of resistance, or "bad metallic behavior" where the resistivity grows without bound with increasing temperature. Translationally invariant higher-dimensional generalizations of the Sachdev-Ye-Kitaev model can capture a variety of phenomena arising purely from electron-electron interactions, including local criticality, non-Fermi liquid, and marginal Fermi liquid behavior. I will describe the implications of these results for the problem of non-quasiparticle transport at large, local quantum criticality, and fundamental bounds on dissipation rates in quantum systems.

Faculty Host: Rafael Fernandes
To be announced.

Thursday, February 22nd 2018
10:10 am:
Biophysics Seminar in 120 PAN
No Seminar This Week - Biophysical Society Meeting
Speaker: Avery Garon and Scott Thaller
3:35 pm:
Speaker: Erez Berg (University of Chicago)
Subject: Critical Metals: Lessons from quantum Monte Carlo studies

Critical phenomena are one of the cornerstones of classical statistical mechanics. Quantum critical points (i.e., continuous phase transitions at zero temperature) in insulating materials are relatively well understood, by analogy with classical critical points in one spatial dimension higher. In contrast, the theory of quantum critical behavior in metals is still, to a large degree, open. Such metallic critical points are believed to play an important role in the physics of several "strongly correlated" materials, such as high temperature superconductors. Fortunately, many classes of metallic quantum critical points can be simulated efficiently using quantum Monte Carlo without the notorious "sign problem", which often hinders numerical simulations of fermionic systems. I will describe some recent progress along these lines, and how it sheds new light on some of the outstanding puzzles in the field.

Faculty Host: Rafael Fernandes

Friday, February 23rd 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be no seminar this week.
12:20 pm:
Speaker: James Delles, University of Minnesota
Subject: Thermally Activated Hopping over a Barrier in a Mesoscale Permalloy System

Thermally activated hopping between energy minima in a double well system is expected to follow an Arrhenius Law. Experiments have shown that the rate of switching between two wells is proportional to the Boltzmann factor but little work has been done to probe the nature of the characteristic dwell time. A square, permalloy, mesoscale dot with an applied magnetic field can be used to create a double well system to explore the characteristic dwell time. I will show that the characteristic dwell time has an exponential dependence on the height of the barrier. There is a significant quantitative disagreement between accepted models of the dwell time and our results.

Speaker: Daniel Chung (U. Wisconsin, Madison)
Subject: Searching for Axionic Blue Isocurvature Perturbations

If the Peccei-Quinn symmetry breaking field is displaced from its minimum
during inflation, the axion isocurvature spectrum is generically strongly
blue tilted with a break transition to a flat spectrum. A test of this
scenario with the Planck and BOSS DR11 data will be presented. Encouraging
results and its implications for future probes of axions and inflationary
cosmology will be discussed.

Speaker: Attila Kovacs (SAO)
Subject: Far-infrared frontiers

The far-infrared (FIR) and (sub)millimeter bands provide us with unique views of structure formation in the Universe and the Galaxy alike. At these wavelengths we have the most adept probes of active star-formation that sample almost all of the reionized Universe (z~1--10) with essentially no bias. The Sunyayev Zel'dovich effect traces the assembly of galaxy clusters regardless of cosmological distance. Locally, in the Galaxy, FIR polarimetry probes the magnetic environments and dust properties around optically obscured young stars and cores, while FIR spectroscopy can spy on the ices in planetary disks. I will also highlight some of the ground-braking recent and upcoming instrumentation and technologies I work on to can deliver this scientific treasure trove.

3:35 pm:
Speaker: Nahyan Fancy, Department of History, DePauw University
Subject: "Did Humoral Theory Undergo any Changes in Post-Avicennan Medicine? Examples from the Commentaries of Ibn al-Nafīs (d. 1288) and his Successors in Western Eurasia"
Refreshments served at 3:15 p.m.

It has long been maintained that Galenic/Hippocratic humoral theory reigned supreme in Islamic societies from when Greek medical texts were translated into Arabic in the ninth century till the arrival of European colonial powers in the nineteenth. Historians have provided various explanations for the persistence of humoral theory in Islamic societies ranging from the (alleged) religious prohibition against dissection to a predisposition amongst medical writers towards systematizing and summarizing rather than critical inquiry. Yet, medical writers engaged critically with medical theory in their commentaries on the Canon of Medicine and the Epitome. The leading figure in this critical engagement was Ibn al-Nafīs (d. 1288). Underlying his modification of humoral theory was a sustained critique of the Galenic physiological and anatomical understanding of digestion. Consequently, the paper provides evidence for Ibn al-Nafīs conducting anatomical observations on dead animals. Moreover, the fact that his new proposals were debated and accepted by later Islamic physicians counters the prevalent assumption that his works were ignored in the later period, and thus raises the distinct possibility that these new ideas on the humors and digestion were appropriated by Renaissance physicians such as Jean Fernel.

3:35 pm:
To be announced.
4:40 pm:
To be announced.

Monday, February 26th 2018
12:15 pm:
There will be no seminar this week.

Tuesday, February 27th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
Practice Talks for the upcoming Chapman Conference on Particle Dynamics in the Earth's Radiation Belts.
3:30 pm:
Speaker: Samuel Lederer, MIT
Subject: High temperature superconductivity and strange metal behavior near a metallic quantum critical point

It has long been conjectured that quantum critical points (QCPs) are at the root of some of the most fascinating phenomena in the solid state, including the high temperature superconductivity and “strange metal” behavior of cuprate superconductors. Though much progress has been made in the theory of QCPs, those which occur in metals (and are likely relevant to the high temperature superconductors) are still poorly understood despite more than four decades of effort. Using Quantum Monte Carlo techniques, my collaborators and I have performed the first numerically exact simulations of a model which realizes a metallic QCP towards an Ising nematic ordered phase. I will discuss our results, which include numerous phenomena already observed in experiment, and comment on future avenues towards a solution of this difficult and rich problem in quantum statistical mechanics.

Faculty Host: Rafael Fernandes

Wednesday, February 28th 2018
1:25 pm:
Speaker: Various speakers
Subject: APS March Meeting Practice Talks
Speaker:  Hajime Muramatsu, University of Minnesota
Subject: Leptonic Decays of Charmed Mesons at BESIII

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

Thursday, March 1st 2018
08:00 am:
Speaker: Lee Penn, CHEM and Diversity Committee
10:00 am:
Thesis Defense in 110 PAN
Speaker: Eric Bullock, University of Minnesota
Subject: Polarization Angle Calibration and B-Mode Characterization with the BICEP and Keck Array CMB Telescopes
This is the public portion of Mr. Bullock's Thesis Defense. His advisor is Clem Pryke
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Tanner Akkin, Associate Professor of Biomedical Engineering, University of Minnesota
Subject: Development of a Serial Optical Coherence Scanner for Visualizing and Mapping the Brain with Microscopic Resolution

The feasibility of mapping and imaging the brain with microscopic resolution is presented. A serial optical coherence scanner, which combines a polarization-sensitive optical coherence tomography and a tissue slicer, distinguishes white matter and gray matter and visualizes nerve fiber tracts that are as small as a few tens of micrometers. The technique utilizes the retardance contrast that arise due to the myelination of nerve fibers and the axis orientation contrast that determine the 2D orientation of the nerve fibers, and the technique can be adapted to measure the inclination angle of the fiber, completing the 3D orientation. This scanner could reveal biomarkers for disease onset and progression, and support development of therapeutics.

Journal Club is canceled to make time for people to attend the Sara Seager colloquium at at 4:00 p.m.
4:00 pm:
Speaker: Sara Seager, MIT
Subject: Mapping the Nearest Stars for Habitable Worlds
Joint Colloquium with Earth Sciences (Nier Lecture). Note later start time.

Bio:

"Sara Seager is a planetary scientist and astrophysicist at the Massachusetts Institute of Technology where she is a Professor of Planetary Science, Professor of Physics, Professor of Aerospace Engineering, and holds the Class of 1941 Professor Chair. She has pioneered many research areas of characterizing exoplanets with concepts and methods that now form the foundation of the field of exoplanet atmospheres. Her present research focus is on the search for life by way of exoplanet atmospheric “biosignature” gases. Professor Seager works on space missions for exoplanets including as: the PI of the CubeSat ASTERIA; the Deputy Science Director of the MIT-led NASA Explorer-class mission TESS; and as a lead of the Starshade Rendezvous Mission (a space-based direct imaging exoplanet discovery concept under technology development) to find a true Earth analog orbiting a Sun-like star. Among other accolades, Professor Seager was elected to the US National Academy of Sciences in 2015, is a 2013 MacArthur Fellow, is a recipient of the 2012 Sackler Prize in the Physical Sciences, and has Asteroid 9729 named in her honor."

Abstract:

Thousands of exoplanets are known to orbit nearby stars and small rocky planets are established to be common. The ambitious goal of identifying a habitable or inhabited world is within reach. But how likely are we to succeed? We need to first discover a pool of planets in their host star’s “extended” habitable zone and second observe their atmospheres in detail to identify the presence of water vapor, a requirement for all life as we know it. Life must not only exist on one of those planets, but the life must produce “biosignature gases” that are spectroscopically active, and we need to be able to sort through a growing list of false-positive scenarios with what is likely to be limited data. The race to find habitable exoplanets has accelerated with the realization that “big Earths” transiting small stars can be both discovered and characterized with current technology, such that the James Webb Space Telescope has a chance to be the first to provide evidence of biosignature gases. Transiting exoplanets require a fortuitous alignment and the fast-track approach is therefore only the first step in a long journey. The next step is sophisticated starlight suppression techniques for large ground-and space-based based telescopes to observe small exoplanets directly. These ideas will lead us down a path to where future generations will implement very large space-based telescopes to search thousands of all types of stars for hundreds of Earths to find signs of life amidst a yet unknown range of planetary environments. What will it take to identify such habitable worlds with the observations and theoretical tools available to us?

Nier Info:

Professor A.O. Nier

A.O. Nier served as a highly distinguished faculty member of the Physics Department for 42 years starting in 1938. He was actively involved in research up to the time of his death in 1994. A firm believer in “pursuits of knowledge - in areas which cross traditional lines” he had an enormous impact on the geological sciences by his pioneering work on isotope abundances and measurements of many elements which are used in radiometric age determinations of geologic materials. He received many national and international awards in recognition of his discoveries and contributions to Physics, Geological Sciences and many other fields.

Friday, March 2nd 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be no seminar this week.
12:20 pm:
Speaker: Various speakers
Subject: APS March Meeting Practice Talks
Speaker: Andrew Spray, (IBS, Daejon, Korea)
Subject: Constraints and Phenomenology of Semi-Annihilating Dark Matter

Semi-annihilation describes processes with an initial state of two dark matter particles, and a final state of one plus standard model states. It is a generic feature of dark matter whenever the symmetry group enforcing stability is not a discrete Z2. Semi-annihilation changes the expected signals in current dark matter searches. With the bounds on standard thermal dark matter becoming very strong, now is the ideal time to ask to what extent those bounds apply to semi-annihilation, and what interesting parameter space remains. In this talk, explore the parameter space in a generic, bottom-up approach. We discuss the subtleties involved with semi-annihilation of fermionic dark matter, the role of additional unstable dark sector particles, and the interplay of semi-annihilation and the non-perturbative Sommerfeld effect. We discuss how semi-annihilation may relate to various anomalies seen in cosmic ray searches. Finally, we use an effective field theory approach to place limits in as model-independent a fashion as possible. We find that current searches are effective for processes with coloured final states, but significant model space for semi-annihilation still remains.

Speaker: Dr. Mateusz Ruszkowski, U. Michigan
Subject: The role of cosmic rays in stellar and supermassive black hole feedback

I will discuss the role of cosmic rays in stellar and supermassive black hole feedback. I will argue that cosmic rays are likely to play a very important role across a large range of distance scales -- from the scales of individual galaxies to the scales comparable to those of cool cores of galaxy clusters.

Regarding the galactic scale feedback, I will focus on supernova and cosmic ray driven winds. Galactic outflows play an important role in galaxy evolution and, despite their importance, detailed understanding of the physical mechanisms responsible for the driving of these winds is lacking. Although cosmic rays comprise only a tiny fraction of interstellar particles by number, they carry energy comparable to that in the thermal gas. I will describe a suite of global 3D MHD numerical simulations that focus on the dynamical role of cosmic rays injected by supernovae, and specifically on the impact of cosmic ray transport along the magnetic fields. Our results show that this microphysical effect can have a significant impact on the wind launching depending on the details of the plasma physics.

Regarding the feedback on galaxy cluster scales, I will discuss results from our simulations of black hole jets in cool cores of galaxy clusters including the effects of cosmic rays. I will argue that cosmic ray heating of the intracluster medium (ICM) may be a very important heating mechanism both in the tenuous and cold phases of the ICM while not violating observational constraints.

While largely an unexplored territory in the context of galactic winds and AGN feedback, cosmic ray feedback is an important process facilitating launching and efficient driving of galactic-scale winds in starburst galaxies and heating of the ICM and remains the subject of intense research.

Faculty Host: Thomas W. Jones
3:35 pm:
Speaker: Alisa Bokulich, Department of Philosophy, Boston University
Subject: "Using Models to Correct Data: Paleodiversity and the Fossil Record"
Refreshments served at 3:15 p.m.

It has long been recognized that models play a crucial role in science, and in data more specifically. However, as our philosophical understanding of theoretical models has grown, our view of data models has arguably languished. In this talk I use the case of how paleontologists are constructing data-model representations of the history of paleodiversity from the fossil record to show how our views about data models should be updated. In studying the history and evolution of life, the fossil record is a vital source of data. However, as both Lyell and Darwin recognized early on, it is a highly incomplete and biased representation. A central research program to emerge in paleontology is what D. Sepkoski has called the “generalized” (or what I prefer to call “corrected”) reading of the fossil record. Building on this historical work, I examine in detail the ways in which various models and computer simulations are being used to correct the data in paleontology today. On the basis of this research I argue for the following: First, the notion of a data model should be disentangled from the set-theoretic, ‘instantial’ view of models. Data models, like other models in science, should be understood as representations. Second, representation does not mean perfectly accurate depiction. Data models should instead be assessed as adequate-for-a-purpose. Third, the ‘purity’ of a data model is not a measure of its epistemic reliability. I conclude by drawing some parallels between data models in paleontology and data models in climate science.

3:35 pm:
Speaker: Miranda Straub, University of Minnesota
Subject: Discussions of papers regarding uncertainty in physics education

We will be discussing papers regarding uncertainty in physics education. The first paper is a model of quantitative uncertainty that can be used in science education, and the second is a study of uncertainty in a physics course. Both papers will be presented with questions to be discussed. Muffins provided.
Learning About Measurement Uncertainties in Secondary Education: A Model of the Subject Matter
Priemer, B. & Hellwig, J. Int J of Sci and Math Educ (2018) 16: 45. https://doi.org/10.1007/s10763-016-9768-0

When and Why Are the Values of Physical Quantities Expressed with Uncertainties? A Case Study of a Physics Undergraduate Laboratory Course
Caussarieu, A. & Tiberghien, A. Int J of Sci and Math Educ (2017) 15: 997. https://doi.org/10.1007/s10763-016-9734-x

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

Monday, March 5th 2018
12:15 pm:
Speaker: Zewei Xiong, UMN
Subject:  Active-sterile neutrino oscillations in the neutrino-driven wind

Neutrino-driven winds from a proto-neutron star made in a core-collapse supernova have been studied extensively as a site for production of elements heavier than the Fe group. The absorption of electron neutrinos and antineutrinos on free nucleons not only provide the heating to drive the wind, but also determine the neutron-to-proton ratio, or equivalently the electron fraction of the wind, which is a critical parameter for nucleosynthesis. Flavor mixing between electron neutrino (antineutrino) and a sterile species that lacks normal weak interaction can potentially impact the dynamics and nucleosynthesis of the wind. We have implemented this active-sterile mixing in a steady-state model of the wind. We find that mixing with a sterile neutrino of ~1eV in mass can significantly affect the electron fraction and hence, nucleosynthesis in the wind.

Faculty Host: Yong-Zhong Qian

Tuesday, March 6th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.
2:30 pm:
Speaker: Jennifer Barnes, Columbia University
Subject: Nuclear Physics with Multi-Messenger Astronomy
Candidate for the Nucear Theory Assistant Professor position

The first detection in August 2017 of a binary neutron star merger in gravitational and electromagnetic waves marked the beginning of the era of multi-messenger astronomy. Future detections of neutron star-neutron star (NSNS) and neutron star-black hole (NSBH) mergers will allow astrophysicists to understand these systems in unprecedented detail, and test key theories about these exotic events. Two questions are especially interesting from a nuclear physics standpoint. First, what is the structure of ultra-dense neutron stars? Second, what is mergers' role in seeding the Universe with heavy elements synthesized via rapid neutron capture (the r-process)?
I will discuss how observations of mergers can help us answer these questions.
I will focus particularly on the radioactive transients that accompany mergers (the so-called "kilonovae"), and explain how recent theoretical advances allow us to use kilonova observations to constrain open questions in nuclear astrophysics.

Wednesday, March 7th 2018
1:30 pm:
No Seminar this week. APS March Meeting.
To be announced.

Thursday, March 8th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Elizabeth Smith (Elias Puchner lab), School of Physics and Astronomy, University of Minnesota
Subject: Characterization of Ire1 interactions and dynamics with quantitative super-resolution microscopy

Quantitative Super-Resolution Microscopy is a powerful technique to study biological processes below the diffraction limit. In this work, we employ our intracellular calibrated Photoactivated Localization Microscopy (PALM) technique to perform quantitative molecular counting of proteins involved in the unfolded protein response (UPR). The UPR is a signaling pathway which dynamically regulates endoplasmic reticulum (ER) protein folding capacity in response to cellular stress. As is true with many signaling pathways, the spatiotemporal organization of the UPR-specific biomolecules is an inherent feature of the pathway activation and downstream response. Specifically, in response to stress, Ire1 (a bifunctional transmembrane kinase/endoribonuclease) oligomerizes and forms discrete signaling clusters which recruit and splice an mRNA encoding a transcription activator. Using PALM in conjunction with traditional fluorescence microscopy we characterize the interactions and dynamics of Ire1 at wild type expression levels in yeast cells. Specifically, we quantify the oligomeric state, of Ire1 under stressed and unstressed conditions, track the motion of Ire1 during signaling activity, and determine the sensitivity and resolution of spatial cross-correlation in a model system combining traditional and super-resolution fluorescencemicroscoy in the same protein construct (Ire1_yeGFP_mEos2). Finally we perform colocalization experiments with downstream UPR biomolecules to further characterize the role of Ire1 signaling centers in control of gene expression. This study provides insight into the spatiotemporal organization of Ire1 and its downstream partners in the signaling response of the UPR.

Speaker: Trevor Knuth and Terry Jones
3:35 pm:
Tate Grand Opening

Friday, March 9th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be a special nuclear physics seminar on Tuesday this week.
12:20 pm:
There will be no seminar this week.
Speaker: Stephen Martin (Northern Illinois U.)
Subject: Quasi-fixed points from scalar sequestering in supersymmetry

The little hierarchy problem of supersymmetry has to do with the question of why the electroweak breaking scale is small compared to the increasingly stringent lower limits on superpartner masses from the LHC. I discuss the possibility of addressing this problem by using hidden sector superconformal renormalization effects. This drives the soft supersymmetry breaking scalar squared mass terms in the Minimal Supersymmetric Standard Model towards quasi-fixed points in the infrared. I discuss the features of such models, and the extent to which the quasi-fixed point effects may ameliorate the little hierarchy problem.

Speaker: David Sand, U. Arizona
Subject: Unveiling the Physics and Progenitors of Cosmic Explosions with a One Day Cadence Supernova Search

Supernovae (SNe) are a linchpin for understanding the chemical evolution and star formation history of the Universe. Despite progress, some of the most basic questions about SNe persist, and we seek to answer the question: What are the explosion mechanisms and progenitor star systems of SNe? In the early hours to days after explosion, SNe provide clues to how they explode, and what their
progenitor star systems were. Observing these ephemeral signatures requires a fast search cadence and immediate spectroscopic response, a dual feat which has been difficult to achieve. Motivated by the need to discover, and study, SNe within the first day of explosion, we have begun a one-day cadence SN search of nearby galaxies (D<40 Mpc; also known as the DLT40 Survey) with a PROMPT 0.4-m telescope directly tied to the robotic FLOYDS spectrographs, a pair of instruments that I helped to develop. Here I will highlight our team's initial discoveries, with an eye towards what will be achievable with future time domain
surveys -- perhaps including nearly automated follow-up of LSST transients and Advanced LIGO gravitational wave events with the suite of Steward Observatory's small telescopes.

Faculty Host: M. Claudia Scarlata
3:35 pm:
There will be no colloquium this week
3:35 pm:
Speaker: Karl A. Smith, Morse-Alumni Distinguished University Teaching Professor, Professor of Civil, Environmental and Geo- Engineering, Emeritus, University of Minnesota
Subject: Engineering Education Research: Emergence, Current Status, and Future Directions

Engineering education research has been part of the landscape of engineering education for many years and began to be formalized with the creation of the American Society for Engineering Education Educational Research and Methods Division over 40 years ago. The field achieved significant advancement with the creation of PhD granting engineering education departments in the mid-2000s.
The seminar focuses on the historical roots of engineering education research, summarizes the current status, and offers some thoughts on the future.
The speaker has been active in engineering education research since the early 1970s and played a major role in the development of the first engineering education PhD granting department.

4:40 pm:
Speaker: Lee Penn
Subject: Diversity Committee workshop

Tuesday, March 13th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
No Seminar this week, spring break

Thursday, March 15th 2018
08:00 am:
Untitled in Physics
08:00 am:
Untitled in Physics
10:10 am:
Biophysics Seminar in 120 PAN
No Seminar This Week (Spring Break)
Speaker: No Journal Club - Spring Break
3:35 pm:
Subject: There will be no colloquium this week due to Spring Break

Friday, March 16th 2018
SPRING BREAK - No seminar this week
Speaker: No colloquium this week - Spring Break

Monday, March 19th 2018
12:15 pm:
No Seminar This Week

Tuesday, March 20th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: David Malaspina, LASP, University of Colorado
Subject: Plasma Boundaries: Bridging Macro-Scale and Micro-Scale Plasma Physics

Plasma physics research is frequently focused on either macro-scale or micro-scale processes, often treating them as independent. Yet recent advances in spacecraft instrumentation, simulation, and laboratory studies are breaking down that paradigm, demonstrating that interactions between large and small scales are critical to understand and predict the behavior of systems as diverse as laboratory plasmas, the solar wind, and the terrestrial magnetosphere. In each of these systems, plasma boundaries act as a bridge between scales. Macro-scale plasma motions drive boundary formation, micro-scale instabilities develop or are spatially sorted as a consequence of these boundaries, and finally, the aggregate effect of many micro-scale interactions modifies the macro-scale system. Examples of interaction between macro- and micro-scale physical processes mediated by plasma boundaries in laboratory plasmas, the solar wind and the terrestrial inner magnetosphere will be discussed, with a focus on observational data.

3:30 pm:
Speaker: Laxman Raju Thoutam and Sajna Hameed.
Subject: Novel Electronic and Magnetic Properties in Rare-Earth Titanates: YTiO3 & NdTiO3.

Wednesday, March 21st 2018
1:25 pm:
Speaker: Li He, University of Minnesota
Subject: Optomechanical measurement of photon spin angular momentum and optical torque in integrated photonic devices
This week's sack lunch talk will be on Wed. at the usual CM seminar time and place

Photons carry spin angular momentum when circularly or elliptically polarized. During light-matter interaction, transfer of angular momentum induces optical torque. Here, we demonstrate the measurement of the spin angular momentum of photons propagating in a silicon waveguide and the use of optical torque to actuate rotational motion of an optomechanical device. We show that the sign and magnitude of the optical torque are determined by the photon polarization states that are synthesized on the chip. Our study reveals the mechanical effect of photon’s polarization degree of freedom and demonstrates its control in integrated photonic devices.

Faculty Host: Paul Crowell
2:30 pm:
Speaker: Aleksey Cherman, University of Washington
Subject: Symmetries, order parameters, and the phase diagram of nuclear matter
Candidate for the Nucear Theory Assistant Professor position

The phases of matter at extreme temperatures and densities are essentially determined by strong nuclear interactions. But for most temperatures and densities, we lack the theoretical tools to efficiently study QCD, the quantum field theory describing the strong nuclear force. For instance, in much of the phase diagram of QCD, there are very few well-defined order parameters to label its phases. I will describe recent advances in understanding the symmetries and order parameters of QCD, with a focus on the implications for understanding the phase diagram of nuclear matter as a function of temperature and density.

To be announced.

Thursday, March 22nd 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Yahor Savich (David Thomas lab), School of Physics and Astronomy, University of Minnesota
Subject: Myosin Orientation in a Functioning Muscle Fiber With High Angular Resolution

We have measured the orientation of myosin in a muscle fiber bundle using electron paramagnetic resonance (EPR) and a bifunctional spin label (BSL), with angular resolution of a few degrees. Despite advances in cryo-EM, fluorescence, and small-angle X-ray diffraction, these techniques do not provide high-resolution structural information about myosin heads in vitro under functional conditions. A pair of (i,i+4) Cys residues were engineered on an alpha-helix in the regulatory light chain (RLC). By exchanging endogenous RLC with BSL-labeled RLC on oriented muscle fibers, we were able to resolve angular distributions in several biochemical states due to the stereospecific attachment of BSL’s two disulfide bonds. In this setup, the accurate determination of BSL’s angular coordinates allowed us to determine the orientation of individual structural elements with respect to the muscle fiber axis. Addition of ATP in the absence of Ca, relaxing the muscle, shifted the orientational distribution to a much more disordered distribution. This work is inspired by growing therapeutic interest in super-relaxed myosin state, which predicts presence of order in relaxation.

Speaker: Sharan Banagiri and Larry Rudnick
3:35 pm:
Speaker: Pablo Jarillo-Herrero (MIT)
Subject: Magic Angle Graphene: a New Platform for Strongly Correlated Physics

The understanding of strongly-correlated quantum matter has challenged physicists for decades. Such difficulties have stimulated new research paradigms, such as ultra-cold atom lattices for simulating quantum materials. In this talk I will present a new platform to investigate strongly correlated physics, based on graphene moiré superlattices. In particular, I will show that when two graphene sheets are twisted by an angle close to the theoretically predicted ‘magic angle’, the resulting flat band structure near the Dirac point gives rise to a strongly-correlated electronic system. These flat bands exhibit half-filling insulating phases at zero magnetic field, which we show to be a Mott-like insulator arising from electrons localized in the moiré superlattice. Moreover, upon doping, we find electrically tunable superconductivity in this system, with many characteristics similar to high-temperature cuprates superconductivity. These unique properties of magic-angle twisted bilayer graphene open up a new playground for exotic many-body quantum phases in a 2D platform made of pure carbon and without magnetic field. The easy accessibility of the flat bands, the electrical tunability, and the bandwidth tunability though twist angle may pave the way towards more exotic correlated systems, such as quantum spin liquids.

Friday, March 23rd 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be a special nuclear physics seminar on Wednesday this week.
12:20 pm:
Speaker: Daniel Sheehy, LSU
Subject: Interface symmetry and non-helical states in topological insulator-semiconductor heterostructures
Note: this seminar is in addition to the one on Wednesday. Please note change of day, time and room, This week only.

Topological insulators (TIs) possess topologically-protected helical
surface states that are immune to non-magnetic disorder and described
by a relativistic "Dirac" Hamiltonian. Similar states are expected
at the interface between a TI and any topologically trivial material.
I will discuss recent work showing that the interface states at the
boundary between a topologically-trivial semiconductor (SE) and a TI
possess a much richer phenomenology compared to the helical surface
states, including complex spin textures and broken helicity.

Faculty Host: Rafael Fernandes
Speaker: Gokce Basar (U. Illinois, Chicago)
Subject: Going with the flow: a solution to the sign problem

I will explore the generalization of the Feynman path integral in quantum field theory to complexified fields, and explain how it can be utilized to tackle the famous "sign problem". The sign problem prevents first principle studies of real-time dynamics and finite density systems via lattice field theory and appears in many different areas in physics. I will discuss both conceptual and computational aspects of this idea and give examples of several interacting quantum field theories where it successfully solves the sign problem.

Speaker: Dr. Jordan Stone, U. Arizona
Subject: Thermal Infrared Probes of Exoplanetary Systems with LBTI

Understanding the gas-giant planet formation process is confused by the fact that it appears multiple formation routes produce objects a few times the mass of Jupiter, where the low-mass tail of the stellar mass function and the high-mass tail of the planet mass function overlap. Distinguishing the formation route for particular objects is challenging but important to create the clean samples necessary to constrain both the planet formation process and the tail-end of the star/brown dwarf-formation process. In particular, constraining the disk-based planet formation mechanism for gas-giants is important because their dynamical dominance affects the formation of terrestrial and ice-giant planets. System architecture and atmospheric composition both provide formation indicators for gas-giants because disk-based formation results in non-hierarchical orbits and atmospheric metal enrichment, as seen in Jupiter and Saturn. I will discuss two programs which I lead with LBTI to probe the outer architecture of planetary systems and to characterize the atmospheres of gas-giant exoplanets. I will also provide an update on the LBTI HOSTS survey for exozodiacal dust around nearby stars. HOSTS is nearing completion and will provide essential information for the design of future space missions that aim to image habitable zone terrestrial planets in reflected light.

Faculty Host: Charles E. Woodward
3:35 pm:
Speaker: Rebecca Kluchin, Department of History, California State University - Sacramento
Subject: "Court-Ordered Cesarean Sections in 1980s America"
Refreshments served at 3:15 p.m.

In June 1987, Angela Carder was twenty-seven years old, married, pregnant, and in remission from cancer. Twenty-five weeks into her pregnancy, she learned that the disease had returned and metastasized in her right lung. Her prognosis was terminal and her condition deteriorated rapidly. When George Washington University Hospital administrators learned that Carder was dying and lacked a plan to save her fetus, they initiated an emergency legal hearing to determine their responsibility to her pregnancy. A judge ordered Carder to undergo an immediate cesarean section. The baby lived two hours. Carder died two days later.

Carder’s parents appealed the decision and in 1990, the District of Columbia Court of Appeals ruled in their favor. The Carder case became national news and entered popular culture when the popular television show LA Law ran an episode based on it. But the Carder case did not occur in a vacuum; in fact, one month before Carder died, the New England Journal of Medicine published an article that revealed twenty-one prior attempts of court-ordered cesarean sections, eighteen of which were successful. Eighty-one percent of patients forced to undergo surgery were women of color and twenty-four percent were non-English speakers. The media attention granted to the Carder case obscured the other forced cesareans and erased women of color from the story. This paper reveals this hidden reproductive history, places it in the context of other reproductive abuses, and locates women of color at the center of the story instead of on the periphery. It argues that court-ordered cesarean sections simultaneously continued the long history of reproductive abuses directed at women of color and represented a new form of abuse specific to the post-Roe era and the politics of legal abortion.

3:35 pm:
Speaker: Brita L. Nellermoe, University of St. Thomas, St. Paul, MN
Subject: Piaget and Vygotsky as a Foundation for Physics Education

The educational psychology of Swiss psychologist Jean Piaget and Soviet psychologist Lev Vygotsky shaped the 20th Century's understanding of how children and adults learn. These learning theories are the basis for much of the late 20th and early 21st century reform of science education in the United States. This talk will discuss the similarities and differences of Piaget and Vygotsky's theories of learning and how they apply to current Physics Education curriculum.

4:40 pm:
Subject: Special topics - auxiliary skills

Monday, March 26th 2018
12:15 pm:
Speaker: Liliya L.R. Williams, UMN
Subject: Relaxation of dark matter halos: distribution in energy and angular momentum

The problem of figuring out the properties of steady-state configuration of dark matter halos has a long history. I will recap some of that, including our contribution to it. I will summarize our results concerning relaxation in terms of energy, and discuss our ongoing work on incorporating angular momentum. I will also present a comparison of theoretical predictions with observations and simulations.

Tuesday, March 27th 2018
Speaker: Michael Fogler, University of California, San Diego
Subject: Hyperbolic waves in Nature: from nano to Ter(r)a

Waves with a hyperbolic dispersion relation are exotic yet surprisingly widespread phenomena that occur in anisotropic media with internal resonances. Such media have been investigated in numerous fields, ranging from condensed matter physics to plasma physics to optics to fluid dynamics and geophysics. Hyperbolic waves can be found in magnetic materials, in both usual and topological insulators, in superconductors, as well as in our oceans, beaches, atmosphere, and space. The characteristic lengths and frequencies of such waves vary vastly, from atomic to cosmic. However, they all exhibit certain common attributes, such as strict directionality, diverging density of states, and anomalous reflection. This talk will contain a primer on hyperbolic materials, a recipe for the death ray, and a report on our nano-optics studies of hyperbolic phonon-polaritons in new quasi-2D materials such as graphene and hexagonal boron nitride.

References:

1. L. V. Brown et al, “Nanoscale Mapping and Spectroscopy of Nonradiative Hyperbolic Modes in Hexagonal Boron Nitride Nanostructures,” Nano Lett. 18, 1628 (2018).
2. A. J. Giles et al., "Imaging of Anomalous Internal Reflections of Hyperbolic Phonon-Polaritons in Hexagonal Boron Nitride," Nano Lett. 16, 3858 (2016).
3. S. Dai et al., “Subdiffractional focusing and guiding of polaritonic rays in a natural hyperbolic material,” Nature Comms 6, 6963 (2015).
4. S. Dai et al., “Tunable Phonon Polaritons in Atomically Thin van der Waals Crystals of Boron Nitride”, Science 343, 1125 (2014).

Faculty Host: Boris Shklovskii

Wednesday, March 28th 2018
2:30 pm:
Speaker: Paul Canfield (Iowa State)
Subject: Synthesis as the Heart of New Materials Physics
Note special time: seminar starts at 2:30 (not 1:25)

Design, discovery, growth and characterization of novel materials is at the heart of New Materials Physics. One of the key steps is deciding what materials to study or try to grow. In this talk I will try to enunciate and elaborate the motivations for making/studying specific compounds. Many examples from current research will be touched upon and discussed. Humor of all types will be used to lighten the load and make the time fly by.

Faculty Host: Martin Greven
3:30 pm:
Space Physics Seminar in Physics 201-20
Speaker: Barry Mauk, APL
Subject: Comparing the energetic particle populations of planetary magnetospheres

We compare planetary magnetospheres in different ways. Do we observe the same phenomenology? Are the same physical processes in play? It is, in fact, a challenge to compare planetary space environments quantitatively in a fashion that leads to a more predictive understanding. I examine here the differences and similarities of the strongly magnetized planetary magnetospheres of the solar system by examining their most energetic particle populations. For both trapped electron radiation and energetic ions comprising ring current populations, updated and extended versions of the classic Kennel-Petschek theory provide reasonable metrics for quantitatively comparing the populations of all of the strongly magnetized planetary magnetospheres. These comparisons are substantially revealing with regard to the character and states of the space environments of the respective planets. Comparisons between Earth and Jupiter are of particular interest in that these two environments are representative of the extremes of magnetospheric conditions; one the canonical solar-wind-driven magnetosphere and the other the canonical rotationally-driven magnetosphere. And yet, both are extremely active and energetic in their own ways.

Faculty Host: Robert Lysak
To be announced.

Thursday, March 29th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Wesley Errington, Molecular Cell Engineering Laboratory, University of Minnesota
Subject: Integrating experimental and computational approaches to elucidate mechanisms of binding in multivalent proteins

Multivalent proteins are ubiquitous in nature and can provide unique, exploitable properties in therapeutic applications such as increased affinity or multi-target specificity. Despite the importance of these proteins in fundamental and applied biomedical research, mechanistic quantitative descriptions of their binding kinetics are limited. We have considered such multivalent protein-protein interactions to be driven by three key variables: the binding affinity of individual monomer units, the linker length/structure between the monomers, and the overall valency of each multivalent protein. Using model synthetic proteins in which all three of these variables can be independently tuned, we have performed surface plasmon resonance experiments to quantify the kinetics of association and dissociation as a function of affinity, linker, and valency. In parallel, we developed a mechanistic model based on mass-action kinetics that explictly enumerates all possible microstates that participate in the binding reaction. Integration of these quantitative experimental and computational approaches has elucidated a number of interesting findings, including the role of valency in generating non-canonical reaction kinetics, that will be discussed. Our approach should enable better understanding of dynamic behaviors in natural multivalent proteins and lead to more rational optimization of multivalent therapeutics.

Speaker: Brian O'Neill
3:35 pm:
Speaker: Barry Mauk, APL
Subject: New perspectives on Jupiter’s novel space environment and aurora from NASA’s Juno mission

B. H. Mauk, The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA (Barry.Mauk@jhuapl.edu)

Jupiter’s uniquely powerful auroras are thought to be symptoms of Jupiter’s attempt to spin up its space environment and shed angular moment (albeit minuscule amounts). The processes involved connect together such disparate phenomena as the volcanoes of Jupiter’s moon Io and the Jupiter-unique synchrotron emissions imaged from ground radio telescopes at Earth. While the power sources for auroral processes at Earth and Jupiter are known to be very different, it has been expected that the processes that convert that power to auroral emissions would be very similar. NASA’s Juno mission, now in a polar orbit at Jupiter, is dramatically altering this view about how Jupiter’s space environment operates. Auroral processes are much more energetic than expected, generating beams of electrons with multiple MeV energies and with directional intensities that can be more intense than the electrons within Jupiter’s radiation belts. The most intense auroral emissions appear to be generated by processes that have no precedent within Earth auroral processes. And, the auroral generation processes are poorly correlated, unexpectedly, with any large-scale electric currents thought necessary to regulate the interactions between Jupiter’s spinning atmosphere and space environment. These and other findings are discussed, along with presentation of Juno’s broader mission and discoveries.

Faculty Host: Robert Lysak

Friday, March 30th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be no seminar this week.
12:20 pm:
Speaker: Bo Xiong, University of Minnesota
Subject: Haldane Exclusion Statistics: beyond Fermion and Boson

Haldane exclusion statistics is one of the many attempts to interpolate between Fermi and Bose cases. However, the distribution function of Haldane statistics is still an open question, parallel to the well-known Fermi and Bose distribution function. I’ll discuss the negative weight problem of Yongshi Wu’s distribution function of Haldane statistics, Murthy and Shankar’s solution and our improvement.

Speaker: Hooman Davoudiasl (Brookhaven)
Subject: Long Range Dark Matter Forces and New Views on Old Problems

We entertain the possibility that a long range force may act on dark matter. The potential coupling of this force to baryons and leptons could lead to new ways of thinking about some of the open questions in particle physics. Here, we mainly focus on scalar forces with various coupling strengths and ranges and examine some of the ways in which they can affect interpretations of dark matter direct detection, neutrino oscillations, or cosmological data.

Speaker: Lou Stolger, Space Telescope
Subject: The Rates of Supernovae, Far and Near

For nearly two decades, the Hubble Space Telescope has been heavily used to locate supernovae in high redshift environments, with the primary goal of improving constraints on the nature of dark energy. Along the way we have made surprising observations on the nature of supernovae themselves, and clues to their elusive progenitor mechanisms, some of which are difficult to reconcile with observations at much lower redshift. From complete volumetric supernova rate histories that now extend to z > 2 we find type Ia supernova delay-time distributions are consistent with a power law index of -1, but with the fraction of prompt (t_d < 500 Myr) is less than expected from various ground-based surveys. Core collapse supernova rates trace the cosmic star formation rate history, but require stellar progenitors more massive than has been seen in deep studies of nearby events (M > 20 M_sol). I’ll detail some interesting discoveries from our recent campaigns on clusters of galaxies, and also discuss what we expect to find with the James Webb Space Telescope, launching in 2018, and with WFIRST in the 2020s.

3:35 pm:
Speaker: Susan Rensing, Department of Women's & Gender Studies, University of Wisconsin - Oshkosh
Subject: HSTM Alumni Lecture - "‘A Coldly Scientific Venture’: Unwed Mothers and the Eugenic Baby Panic"
Refreshments served at 3:15 p.m.

In January of 1928, the New York World set off a firestorm of controversy with a front page story about a wealthy widow, Grace Burnham, who had “mated lovelessly” as a eugenic experiment. Newspapers rushed to seek out stories of other women who were conceiving eugenic babies by selecting a man purely for reproduction, not for marriage. Unlike the wholesome eugenic babies that won ribbons in Better Baby Contests at state fairs, these eugenic babies were portrayed as potential Frankensteins--creations of science run amok. Moral condemnation raged in editorials across the nation as experts weighed in with their opinions about this alarming trend. This talk will use the eugenic baby panic as a cultural lens to examine fears about science bereft of morality in the late 1920s and early 1930s.

3:35 pm:
Speaker: Jie Yang (PER Group from University of Minnesota)
Subject: Quantify the difficulty of physics problems

Assessment methods are broadly recognised as integral to effective instruction. Student performance on tests are a common way for instructors to gauge their instructional effectiveness. However, Lack of alignments of problem difficulty between instructors, institutions, and courses is the major obstacle to make use of authentic student performance data gathered by most classes and used by instructors. In this presentation, I will describe the development and validation of a simple difficulty assessment for assessing open response physics problems’ difficulty. It quantify the difficulty of physics problems. It can be used to compare test or homework problems , or to craft instruction material.

Monday, April 2nd 2018
12:15 pm:
Speaker: Matt Gomer, UMN
Subject:  Lensing degeneracies and their effect on H_0 measurements

At present, there is a 3σ- discrepancy between the local measurements of H0- and those derived from CMB observations. To explore whether or not this is significant, the current goal is to constrain H0- to within 1%, optimally using methods independent from these two. One potential method is to use the time delays between multiple images of gravitationally lensed system as an absolute measure of distance independent of either the distance ladder or CMB modelling. In order to accomplish this at the 1% level, it is critical that the lens system is modelled to similar precision. Unfortunately, there exist lensing degeneracies such as the mass sheet degeneracy which can result in the same set of observables using different mass distributions. Unless these degeneracies can be broken, measurements of H0- will be biased by an unknown amount. In this talk, I detail current efforts to quantify these biases and explore what the future holds for this method.

Faculty Host: Liliya L.R. Williams

Tuesday, April 3rd 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Xianzhe Jia, University of Michigan, Dept. of Climate and Space Physics and Engineering
Subject: Global MHD Simulations of Saturn’s Magnetosphere

At Saturn’s orbital distance of ~ 9.5 AU, the low solar wind dynamic pressure and weak interplanetary magnetic field interact with the planet to create a magnetosphere that dwarfs Earth’s magnetosphere. While the form of Saturn’s magnetospheric cavity is still the result of solar wind stresses, many properties of the Kronian magnetosphere are determined largely by internal processes associated with the planet’s rapid rotation and the stresses arising from internal plasma sources dominated by the icy moon, Enceladus. Coupling between the planetary ionosphere and the magnetosphere through electric currents plays a vital role in determining the global configuration and dynamics of Saturn’s magnetosphere. To understand the large-scale behavior of the solar wind-magnetosphere-ionosphere interaction, we have applied the global MHD model, BATSRUS, to Saturn that couples the solar wind, the magnetosphere, and the ionosphere and incorporates key mass-loading processes associated with Enceladus and its extended neutral cloud. Here we present results from our global simulations carried out to understand how the various internally and externally driven processes influence Saturn’s magnetosphere, and discuss their implications for interpreting Cassin in-situ observations. We will also show results from an atmospheric vortex model we have developed that offers valuable insight into the physical processes that drive the ubiquitous periodic modulations of particles and fields properties observed by Cassini throughout the Saturnian magnetosphere.

3:30 pm:
Speaker: John Dewey and Joseph Batley, Chemical Engineering and Material Science
Subject: Integration of perovskites into non-local spin valves for the study of spin transport in oxides“

Wednesday, April 4th 2018
1:25 pm:
Speaker: Sung-Sik Lee, Perimeter Institute
Subject: Low-energy effective field theories for non-Fermi liquids

Non-Fermi liquids are exotic metallic states which do not support well defined quasiparticles. Due to strong quantum fluctuations and the presence of extensive gapless modes near the Fermi surface, it has been difficult to understand universal low-energy properties of non-Fermi liquids. In this talk I will discuss recent progress made on field theories for non-Fermi liquids. Based on a dimensional regularization scheme which tunes the co-dimension of Fermi surface, critical exponents that control scaling behaviors of physical observables can be computed in controlled ways. The systematic expansion provides important insight into strongly interacting non-Fermi liquids. This allows us to find the non-perturbative solution for the strange metal realized at the antiferromagnetic quantum critical point in 2+1 dimensions, and predict the exact critical exponents that can be experimentally tested in layered systems.

Faculty Host: Andrey Chubukov
To be announced.

Thursday, April 5th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: James M. Carothers, Department of Bioengineering, University of Washington
Subject:  Multi-state design of kinetically-controlled RNA aptamer ribosensors

Metabolite-responsive RNA regulators that react to changing conditions through molecular interactions are widespread in biology. In many of these systems, kinetic control mechanisms coordinate co-transcriptional RNA folding with metabolite binding and enable outputs that are highly-sensitive and highly-selective to target ligands. Although synthetic riboswitches exhibiting kinetic control have been identified by chance, it has not been possible to intentionally engineer kinetically-controlled RNA aptamer devices. Consequently, kinetic control mechanisms that could otherwise be exploited to overcome functional limits imposed by the thermodynamics of molecular recognition have remained beyond reach. We recently developed a novel approach for multi-state, co-transcriptional RNA folding design that has allowed us to engineer kinetically-controlled RNA aptamer ribosensors. In this architecture, in vitro selected RNA aptamers are coupled through a timer domain to a toehold-mediated strand displacement (TMSD) actuator such that co-transcriptional ligand-binding generates fluorescence from DNA gates through TMSD. We have shown that ribosensors can be transcribed in situ and used to analyze metabolic production directly from engineered microbial cultures, establishing a new class of cell-free biosensors. We found that kinetically-controlled ribosensors exhibited 5-10 fold greater ligand sensitivity than a thermodynamically-controlled device. And, we further demonstrated that a second aptamer, promiscuous for aromatic amino acid binding, could be assembled into kinetic ribosensors with 45-fold improvements in ligand selectivity. I will present these results and discuss the broader implications of this work for engineering RNA aptamer devices and overcoming thermodynamic constraints on molecular recognition through the design of kinetically-controlled responses.

Faculty Host: Vincent Noireaux
Speaker: Nathan Eggen and Roberta Humphreys
3:35 pm:
Speaker: Alessandra Corsi, Texas Tech
Subject: Multi-messenger time-domain astronomy: GW170817 and the future

On 2017 August 17, the field of gravitational-wave (GW) astronomy made the big leagues with a dazzling discovery. After several GW detections of black hole (BH)-BH mergers with no convincing electromagnetic counterparts, advanced LIGO and Virgo scored their first direct detection of GWs from a binary neutron star (NS) merger, an event dubbed GW170817. Soon after the GW discovery, GW170817 started gifting the astronomical community with an electromagnetic counterpart spanning all bands of the spectrum. In this talk, I will review what we have learned from GW170817, what questions remain open, and what are the prospects for future EM-GW studies of the transient sky.

Faculty Host: Vuk Mandic

Friday, April 6th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be no seminar this week.
12:20 pm:
Speaker: Tianbai Cui, University of Minnesota
Subject: Impact of damping on superconducting gap oscillations induced by Terahertz pulses

We investigate the interplay between gap oscillations and damping in the dynamics of superconductors taken out of equilibrium by strong optical pulses with sub-gap Terahertz frequencies. A semi-phenomenological formalism is developed in which damping is incorporated by relaxation and dephasing processes within the electronic subsystem, which correspond to T1 and T2 times in the standard pseudospin language for BCS superconductors. Comparing with data on NbN that we report here, we argue that the superconducting dynamics in the picosecond time scale, after the pump is turned off, is governed by the T2 process.

Speaker: Elena Caceres (U. Texas, Austin)
Subject: Rotating Traversable Wormholes
There will be no colloquium this week.
3:35 pm:
Speaker: Stuart Glennan, Department of Philosophy, Butler University
Subject: “Compositional Minimalism”
Refreshments served at 3:15 p.m.

In her paper, “Causality and Determination,” Elizabeth Anscombe advanced an approach to causation that Peter Godfrey-Smith has dubbed “causal minimalism.” In this approach, causation is not one thing, but many. Causal relations depend upon a heterogeneous set of specific activities – like bonding, pushing, tearing or fighting. My aim in this talk is to pursue a related strategy for compositional relations between parts and wholes – whether these be between atoms and molecules, tissues and organs, or children and families. Composition, like causation, is not one thing, but many – largely because parts are bound into wholes by causal relations.

3:35 pm:
Speaker: Lori Patrick, University of Minnesota
Subject: Active learning: what are faculty and student perceptions across disciplines and how should we train teaching assistants to use it?

Active learning teaching techniques – such as clicker questions, group work, think-pair-share, and other activities – benefit all students and can close the achievement gap for under-represented minority, first-generation, and female students in STEM disciplines. Consequently, many courses have been integrating these techniques into their labs and lectures. Several initiatives have focused on training faculty, however there has been relatively little emphasis, at least in biology, to understand faculty and student perceptions of active learning and how these perceptions differ by discipline. Even less is known about graduate student perceptions of active learning and the best strategies to train teaching assistants to use active learning. This talk will focus on some of the work being conducted in the Department of Biology Teaching and Learning to address these questions.

3:35 pm:
Speaker: Kenji Ishii, Synchrotron Radiation Research Center (SPring-8), Japan
Subject: Momentum-resolved charge and spin excitations in cuprate superconductors
PLEASE NOTE TIME AND DATE CHANGE FOR THIS SEMINAR.

In the last two decades, energy resolution of resonant inelastic x-ray scattering (RIXS) has been significantly improved, and RIXS is now established as a momentum-resolved spectroscopy using synchrotron radiation x-rays. Since the beginning of RIXS, cuprate superconductors have been intensively studied. In addition to the interest of superconductivity at the high transition temperature and related phenomena, such as pseudogap and a competing phase with charge order, doped cuprates are important and suitable for the study of the electronic structure of the doped Mott insulator. This is because relatively simple theoretical models with a few orbitals are applicable to describe the electronic structure near the Fermi energy. I will present charge and spin excitations in cuprates observed with RIXS at Cu K-, Cu L3- and O K-edges focusing on the energy range from eV to sub-eV. In this range, charge and spin excitations show characteristic momentum dependence with respective energy scale of hopping energy of electron (t) and exchange interaction of spin (J).

Faculty Host: Martin Greven

Monday, April 9th 2018
12:15 pm:
Speaker: Jose Diego, Consejo Superior de Investigaciones Cientificas, CSIC
Subject: The Universe at Extreme Magnification

Galaxies and galaxy clusters can magnify objects at cosmic distances by large factors. To first order the maximum possible magnification depends on i) the mass of the lens and ii) the size of the background object. Small objects, like stars, can be magnified by factors of several thousand when the lens is a galaxy cluster. Kelly et al. 2018 discovered the first star at cosmological distance magnified by such extreme factors. I will show how the properties of the magnification can be altered by intervening microlenses (from the macrolens) and how this can be used to constrain the amount of dark matter that is in compact form. Gravitational Waves (GW) are another example, where the signal originates from an incredibly small source. I will show how the most massive events detected by LIGO can be re-interpreted as strongly lensed events at z~1-2 by groups of galaxies or small clusters at z~0.3.

Faculty Host: Patrick Kelly

Tuesday, April 10th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.

Wednesday, April 11th 2018
1:25 pm:
Speaker: Xiaojia Wang (University of Minnesota)
Subject:  Ultrafast Optical Characterization of Thermal Transport in Micro/nanostructured Materials and across Interfaces
Faculty Host: Paul Crowell
Speaker: Ruchi Gupta, Southern Methodist University
Subject: Measurement of gluon fusion and vector boson fusion Higgs boson production cross-sections in the H→ WW*→ eνμν decay channel in pp collisions at sqrt(s) = 13 TeV

The Higgs boson production cross-sections in proton-proton collisions are measured using the events in the H→WW*→eνμν decay channel. The measured cross sections probe the Higgs boson couplings to heavy bosons and to gluons. The proton-proton collision data were produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb−1.

Thursday, April 12th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Aaron Engelhart, Department of Genetics, Cell Biology, and Development, University of Minnesota
Subject:  Hold the water! Probing nucleic acid hydration with alternative solvents

Nucleic acids adopt a myriad of roles in life ranging from their well-known role in simple information transfer (in DNA and mRNA) to functional behaviors including catalysis (in ribozymes including the ribosome) and ligand binding (in riboswitches). The folding of these polymers is intimately connected with the environment afforded by the solvent in which they fold: water. Water dictates the folding behavior of nucleic acids in a variety of ways, including hydrophilic interactions (with the phosphate backbone as well as dissolved cations); nonclassical hydrophobic interactions (which promote base stacking); and minor groove binding of water (as well as cations), which has been known since the first atomic-resolution crystal structures of DNA shown by Drew and Dickerson. We recently showed that, remarkably, nucleic acids can form stable secondary structures in an essentially anhydrous solvent - a so-called "deep eutectic solvent" (DES) formed from a 2:1 molar mixture of urea and choline chloride. Despite the absence of water, a range of secondary structures fold in DES. I will discuss our results using alternative solvents to examine the role of hydration in nucleic acid folding.

Speaker: Karl Young
3:35 pm:
Speaker: Doug Glenzinski, Fermilab
Subject: A Rare Opportunity - the Mu2e Experiment at Fermilab

The muon, a heavy cousin of the electron, was discovered in 1936. Since
that time they have only ever been observed to do one of two things: 1)
scatter or 2) decay into final states that include a combination of
charged leptons and neutrinos. A new experiment at Fermilab - the Mu2e
experiment - is going to look for a third thing: a muon trapped in atomic
orbit that interacts with the nucleus to produce an electron and nothing
else. This is a process that's predicted to occur very very rarely, maybe
once every 10^15 decays,(or less!). But this very rare decay will probe
new physics mass scales up to 10,000 TeV/c^2 and may hold the key to
understanding physics at its most fundamental level. The Mu2e experiment
is an ambitious endeavor whose goal is to observe this very rare
interaction for the first time - a discovery that could help reveal a new

Faculty Host: Kenneth Heller

Friday, April 13th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be no seminar this week.
12:20 pm:
Speaker: Zhen Jiang, University of Minnesota
Subject: The temperature and doping dependence of the inverse spin Hall effect in GaAs

The study of spintronics includes 3 tasks: the generation, manipulation and detection of spin polarization. The inverse spin Hall effect(ISHE), which converts pure spin currents to electric currents, is an important way to detect spin accumulation. Although it has been used widely, its origins are not necessarily understood. For example, the ISHE in GaAs has been found to be surprisingly large in n-GaAs(doped with Si), and at low temperatures it is very sensitive to hyperfine fields. In this talk, I will present my measurements on devices with channels of varying doping at different temperatures. The goal of this experiment is to study the ISHE in a regime where the complications of hyperfine interactions are absent.

Speaker: Kristian Jensen (San Francisco State U.)
Subject: A Zoo of Bosonization Dualities

There has been substantial progress toward establishing a landscape of non-supersymmetric dualities in three dimensions. These dualities equate Chern-Simons gauge theories coupled to matter, and relate theories of fundamental fermions to those of fundamental bosons. I will discuss a proposal for a new “master” duality between Chern-Simons theory coupled to fundamental bosons and fermions, which if correct summarizes most of these “3d bosonization” dualities.

Speaker: No speaker this week.
Faculty Host: M. Claudia Scarlata
3:35 pm:
Speaker: Lawrence Principe, Department of History of Science & Technology, Johns Hopkins University
Subject: "Wilhelm Homberg’s Laboratories and Instruments: Doing Chymistry in Early Modern France"
Refreshments served at 3:15 p.m.

One of chemistry’s chief characteristics is its union of head and hand, theory and practice, and the subsequent need for workspaces and instruments doing chemistry practically. Wilhelm Homberg (1653-1715), the chief chymist of the Parisian Académie Royale des Sciences, worked in many different spaces over the course of his remarkable career. Starting in 1702, he worked in what was called at the time “the most magnificent laboratory that chymistry had ever known”--a workspace specially-built for him in the Royal Palace by his patron (and collaborator) Philippe II, duc d’Orléans, the future Regent of France. Philippe also outfitted this laboratory with the most extraordinary--and costly--scientific instrument of time, and Homberg enjoyed exclusive access to it. This talk examines the various workspaces Homberg used, highlighting the results that he achieved and their relation to spaces and instruments, the role of patronage, and the changing nature of chymistry in the period.

3:35 pm:
Speaker: Laura McCullough, UW-Stout

Women in Physics Leadership: Women’s representation in physics has increased to 20% and now is holding steady. Women’s representation in physics leadership positions is much smaller. Whether as department chair, journal editor, or professional society president, women are much less visible as leaders in the physics community. Data on women’s leadership in physics will be shared, and discussion will be encouraged.

Monday, April 16th 2018
12:15 pm:
No Seminar this Week
3:35 pm:
Speaker:  Professor Sudhakar Prasad, University of New Mexico and University of Minnesota
Subject: The Modern Imaging Paradigm: There is Plenty of Room in the Middle

Every modern imaging system is comprised of optical, sensing, and computational modules that work in an integrated fashion to perform a dedicated imaging task as efficiently as possible. This new paradigm of imaging, called integrated or computational imaging, has enabled spectacular advances in probing remote objects and environments. I will illustrate this paradigm with an important application, namely Lord Rayleigh's classic resolution limit on the separability of two closely-spaced point sources from their images. I will show why such a limit has become a mere relic, one that has been usurped spectacularly by modern advances in image processing, new imaging methodologies, and ingenious work-arounds. Yet the best pair resolution that one can hope to achieve seems to be fundamentally limited by the number of signal photons available when making direct image measurements on the source pair. I will discuss a new approach of pair super-resolution that can qualitatively improve upon this seemingly insuperable photon limit, with quantum estimation theory revealing the ultimate bound on this phenomenon. Rather surprisingly, as I will also show, one can attain this quantum bound in certain limits in all three spatial dimensions with purely classical measurements that are not image based, but rather utilize coherent projections of the optical wave front. Phase does matter, even when imaging incoherent objects.

Tuesday, April 17th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Kendra Bergstedt, University of Minnesota
Subject: An Investigation of the Dayside Response of the Magnetosphere to Interplanetary Shocks: Dependence on Shock Parameters and Interplanetary Magnetic Field
This is the honors thesis presentation for Ms. Bergstedt
Faculty Host: Cynthia Cattell
1:30 pm:
Thesis Defense in PAN 110
Speaker: Timothy Peterson, University of Minnesota
Subject: Characterization of spin transport, torques, and dynamics in Heusler compound-based epitaxial structures
This is the public portion of Mr. Peterson's Thesis Defense. His advisor is Paul Crowell.
3:30 pm:
Speaker: Zach Anderson and Yang Tang, University of Minnesota
Subject: Doping dependence of the antiferromagnetic response of HgBa2CuO4+δ

Antiferromagnetic correlations have been argued to be the cause of the d-wave superconductivity and of the pseudogap phenomena exhibited by the cuprates. Neutron scattering measurements of the antiferromagnetic response have been reported for a number of cuprates, but our study of structurally simple HgBa2CuO4+δ (Hg1201) shows several features distinct from what has been found in other materials. In particular, at most dopings and temperatures we see a gapped Y-shaped magnetic dispersion in contrast to the X-shaped response seen in other cuprates. We will discuss our ongoing efforts to understand the doping dependence of the magnetic spectrum in Hg1201.

Wednesday, April 18th 2018
1:25 pm:
Speaker: Morten Christensen (University of Minnesota)
Subject:  Magnetic order in the iron pnictides and the impact of spin-orbit coupling

The iron pnictides represent a new family of unconventional superconductors in which superconductivity appears in close proximity to a magnetically ordered phase. In this talk I will review the magnetic order of the iron pnictides and discuss recent discoveries in the magnetic phase diagram, focusing on the reorientation of magnetic moments observed to occur in hole-doped compounds. Considering the impact of magnetic fluctuations on the phase diagram I will argue that even the modest spin-orbit coupling observed in iron pnictides has important consequences and cannot be neglected.

Faculty Host: Paul Crowell
To be announced.
7:00 pm:
Kaufmanis Public Lecture in McNamara Alumni Center
Speaker: Victoria Kaspi, McGill University

In 2007, astronomers discovered a new mysterious cosmic phenomenon: Fast Radio Bursts. These events consist of short, intense blasts of radio waves arriving from far outside our Milky Way galaxy. Their origin is unknown, however Fast Radio Bursts appear ubiquitous in our Universe, with roughly 1000 arriving every day over the full sky. I will discuss the Fast Radio Burst mystery and what is presently known about it, and describe a revolutionary new radio telescope being built in Canada that will soon enable astronomers worldwide to make major progress in our understanding of the FRB puzzle.

Thursday, April 19th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Ashim Rai, (postdoc in Shiv’s lab) Department of Genetics, Cell Biology and Development, University of Minnesota
Subject: Biophysical regulation of myosin VI motility by cargo adaptor proteins

: Cargo transport by motor proteins organizes the cell interior. On cellular cargoes, the binding of motor proteins is mediated by cargo adaptor proteins. Initially thought of as passive scaffolds for motor proteins, cargo adaptor proteins have recently been shown to directly affect motor function through structural studies. However, a biophysical mechanism of cargo adaptor-mediated regulation of motor activity is still lacking. In this study, we have tried to address this problem in the context of the minus-end directed actin motor, Myosin VI. Through direct measurements of adapter-mediated changes in myosin VI motility, conformation and dimerization, we have tried to establish a structure-function relationship between myosin VI and its cargo adaptor proteins. We find that binding to cargo adaptor has a potentiating effect on myosin VI velocity and processivity which is mediated through a combination of auto inhibition release, lever arm extension and dimerization of the myosin VI motor.

Speaker: Evan Tyler and John Phillips
3:35 pm:
Speaker: Victoria Kaspi, McGill University.

Fast Radio Bursts (FRBs) are a newly discovered astrophysical phenomenon consisting of short (few ms) bursts of radio waves.FRBs occur roughly 1000 times per sky per day. From their dispersion measures,these events are clearly extragalactic and possibly generally at cosmological distances. One FRB is known to repeat and indeed has been localized to a dwarf galaxy at redshift 0.2. Nevertheless, the origin of FRBs, whether repeating or not, is presently unknown. In this talk I will review FRB properties as well as highlight efforts to find FRBs, including a new Canadian radio telescope,CHIME, that is predicted to make major progress on the FRB problem.

Friday, April 20th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be no seminar this week.
12:20 pm:
Speaker: Hanteng Wang, University of Minnesota
Subject: Interplay between interaction and disorder: Existence of many-body mobility edge in a modified Sachdev-Ye-Kitaev model.

Sachdev-Ye-Kitaev (SYK) model is a strongly correlated disordered model which exhibits many interesting properties, such as non-Fermi liquid behavior, AdS/CFT correspondence, and maximally chaoticity. In this talk, I will introduce a modified SYK model to investigate the interplay between interaction and disorder numerically. By adding constrain in coupling constant of SYK, a many-body "mobility edge" in the spectrum can be found by checking the nearest neighbor spacing distribution. When choosing a specific basis of many-body Hilbert space, one can find localized and delocalized wavefunction in Fock space. A discussion of connection and difference between chaoticity and locality of the states in this model will also be present.

Subject: SU(5) x U(1)_X grand unification with Minimal Seesaw and Z′-portal dark matter

We propose a grand unified SU(5) x U(1)_X model, where the standard SU(5) grand unified theory is supplemented by minimal seesaw and a right-handed neutrino dark matter with an introduction of a global Z_2-symmetry. In the presence of three right-handed neutrinos (RHNs), the model is free from all gauge and mixed-gravitational anomalies. The SU(5) symmetry is broken into the Standard Model (SM) gauge group at M_GUT = 4 x 10^16 GeV in the standard manner, while the U(1)_X symmetry breaking occurs at the TeV scale, which generates the TeV-scale mass of the U(1)_X gauge boson (Z′ boson) and the three Majorana RHNs. A unique Z_2-odd RHN is stable and serves as the dark matter (DM) in the present Universe, while the remaining two RHNs work to generate the SM neutrino masses through the minimal seesaw. We investigate the Z′-portal RHN DM scenario in this model context, and find that the constraints from the DM relic abundance and the search results for a Z′ boson resonance at the Large Hadron Collider (LHC) are complementary to narrow down the allowed parameter region, which will be fully covered by the future LHC experiments (for the Z′ boson mass < 5 TeV). We also briefly discuss the successful implementation of baryogenesis and cosmological inflation scenarios in the present model.

Speaker: No colloquium - See info for the Kaufmanis Public Lecture on the 18th
3:35 pm:
Speaker: Roberta Humphreys, Minnesota Institute for Astrophysics, University of Minnesota
Refreshments served at 3:15 p.m.

In December 2016, the prominent woman astronomer Vera Rubin passed away. Numerous articles lauding her accomplishments credited Vera with the discovery of dark matter or at least the confirmation of it. Vera was a member of the National Academy of Sciences, a recipient of the National Medal of Science, plus numerous awards and recognition. She was also a strong and often outspoken advocate for women in science. My story begins in 1971 when Margaret Burbidge, the best known woman in astronomy, turned down the Annie Jump Cannon Award of the American Astronomical Society (AAS) on the grounds that it was discriminatory. This was the Society's oldest award and the only one exclusively for women. This created an image crisis for the AAS. One of the consequences was the first Working Group on the Status of Women in Astronomy. Vera and I were on that committee. We established a strong supportive and professional relationship. At one point our research briefly overlapped regarding the motions of stars and gas in galaxies. I'll briefly describe some of the highlights of Vera's discoveries -- including the rotation curves of galaxies and dark matter.

3:35 pm:
Speaker: Jennifer Docktor, University of Wisconsin – La Crosse Dept. of Physics
Subject: Using the Claim, Evidence, and Reasoning Framework to Develop Prospective Teachers’ Scientific Explanations in Physics

The Framework for K-12 Science Education provides a common vision for what students should know and be able to do upon finishing high school. It proposes that students should learn science by engaging in the practices used by scientists, such as planning and carrying out investigations, modeling, and developing explanations based on evidence. However, most prospective K-12 teachers have limited preparation for how to teach science using these practices. In this study, one section of a physical science course for elementary education majors received explicit instruction and scaffolding on using the Claim, Evidence, and Reasoning (CER) framework for constructing scientific explanations and one section served as a comparison group. I will describe the study design, course curriculum, assessment data collected, and scoring rubrics. A preliminary analysis indicates a relationship between prospective teachers’ abilities to construct scientific explanations using the CER framework and their long term retention of physical science content.

4:40 pm:
Career Panel in Tate 120
Subject: Careers in Industry and Academia for Physics PhDs
Everyone welcome, see abstract for full information.

This career panel will give students a taste of some of the career paths taken by UMN graduates and other physics PhDs. Panel members span a variety of jobs in local industry and in academic positions at universities or research labs. Many of the panel participants are alumni of the UMN Physics and Astrophysics PhD programs.

Everyone is welcome. This event is a great opportunity for students to learn about PhD career paths in academia and in industry and to ask our panelists any questions about their experiences. While the panel may be of special interest to graduate students pursuing a PhD, it would also be beneficial to undergraduate students curious about career paths. To aid in planning, please RSVP at this link by Monday, April 16: https://goo.gl/forms/r9QB0eNquCfQUPdz1.

Panel participants:

Mohac Tekmen, Medtronics
Xifeng Han, Seagate
Luis Hernandez, BAE Systems
Dan Endean, Honeywell
Fiona Burnell, University of Minnesota
Gerry Ruch, University of St. Thomas
Jeff Stehr, NASA / Booz Allen & Hamilton

The event will begin at 4:40 with a short presentation on physics PhD career statistics by Shaul Hanany, followed by brief remarks by the panelists. The bulk of the time will be devoted to Q&A. Some time will be reserved toward the end of the event for informal discussion.

Contact Lindsay Glesener (glesener@umn.edu) with any questions about the event.

Monday, April 23rd 2018
12:15 pm:
Speaker: Qi Wen, UMN
Subject: Broadband anti-reflection coatings using “moth-eye” structures in millimeter and submillimeter astronomy

Wasting is evil, let alone wasting the light signal from billions years ago that can potentially reveal the secrets of the Universe. Unfortunately, optical elements in a telescope, such as lenses and filters, reflect part of the light back to sky. In millimeter and submillimeter astronomy, broadband anti-reflection coatings (ARC) are more desired than ever for foreground modeling. In this talk, I will introduce the subwavelength structures (SWS) or so called “moth-eye” structures as an emerging type of broadband ARC in millimeter and submillimeter astronomy.

Faculty Host: Shaul Hanany
4:40 pm:
Speaker: Irene Moskowitz (University of Minnesota)
Subject: Bolometer Response to Elevation Angle in EBEX: How can we detect evidence of inflation in the early universe?
Faculty Host: Paul Crowell

Tuesday, April 24th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Zac Cohen, University of Minnesota
Subject:  STEREO Observations of Waves in the Ramp Regions of Interplanetary Shocks
This is seminar is also the public portion of Mr. Cohen's Masters' Thesis Defense.

Wednesday, April 25th 2018
1:15 pm:
Speaker: Vlad Pribiag (University of Minnesota)
Subject: Spin-Dependent Transport and Superconductivity in SrTiO3-Based Heterostructures
NOTE SPECIAL TIME: Seminar starts at 1:15
Faculty Host: Paul Crowell

Thursday, April 26th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Gianluigi Veglia, Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota
Subject: Role of conformational dynamics on protein kinases function and dysfunction

Eukaryotic protein kinases (EPKs) are phosphoryl transferase that mediate several signaling events and constitute major pharmaceutical targets. cAMP-dependent protein kinase A is a prototypical kinase of paramount biological importance as it is involved in a myriad of cellular processes. Using nuclear magnetic resonance (NMR) spectroscopy, we probed the enzyme’s intramolecular allosteric network along the catalytic cycle. We discovered that kinase A conformational motions are highly organized and correlated during turnover. Fast dynamics in the ps-ns time scale are directly linked to the conformational entropy of binding, revealing the mechanisms for positive and negative allosteric cooperativity that drive both substrate binding and product release. Slow dynamics in the in the micro second to milli second time scale are responsible for the conformational transitions from catalytically incompetent to competent states. Disruption of these dynamics leads to dysfunctional signaling and disease. Since the C-subunit of protein kinase A is highly conserved within the kinase family, the present study offers unprecedented mechanistic insights into intramolecular signaling for designing novel kinase activators or inhibitors.

Speaker: Sourabh Chauhan
3:35 pm:
Speaker: John Bush, MIT
Subject: Hydrodynamic quantum analogs

Droplets walking on a vibrating fluid bath exhibit several features previously thought to be exclusive to the microscopic, quantum realm. These walking droplets propel themselves by virtue of a resonant interaction with their own monochromatic wavefield, and represent the first macroscopic realization of a pilot-wave system of the form proposed for microscopic quantum dynamics by Louis de Broglie in the 1920s. New experimental and theoretical results allow us to rationalize the emergence of quantum-like behavior in this hydrodynamic pilot-wave system in a number of settings, and explore its potential and limitations as a quantum analog.

Faculty Host: J. Woods Halley

Friday, April 27th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
To be announced.
12:20 pm:
Speaker: Kexin Feng, University of Minnesota
Subject: Signatures of unusual edge physics in the specific heat of Kitaev spin liquids

Some new candidate Kitaev spin liquid material has recently been found in the experiment. Qualitative signatures of spin liquids are important to identify them. We try to explore the features of unusual edge physics in the specific heat. We find that, the fluxe excitation has some edge effects in specific heat. We also show that there is zero-temperature degenerate entropy which indicates the existence of gapless edge mode.

Speaker: Mustafa Amin (Rice U)
Subject: Inflation Ends, What’s next ?

How did inflation end? For a broad class of "simple", observationally consistent inflationary models, I will present results regarding: (1) Nonlinear fragmentation and soliton formation in the inflaton field, (2) the equation of state of the universe after inflation. For sufficiently complex models, I will highlight some universal results from stochastic particle production during inflation and reheating, and discuss their implications for initial curvature perturbations from the early universe.

2:00 pm:
Speaker: Masaaki Matsuda, ORNL
Subject: Magnetic correlations in the vicinity of the superconducting state in CrAs and MnP
Please note time and date change for this seminar. This week only.

CrAs and MnP exhibit superconductivity under pressure with a maximum transition temperature of ~2 K at 2 GPa and ~1 K at 8 GPa, respectively. Since Cr and Mn have the spin degree of freedom, elucidating the magnetic contribution to the superconductivity is crucial to understand the pairing mechanism. A helical structure is the magnetic ground state at ambient pressure in both materials. We performed neutron scattering studies in both materials under pressure. With applying pressure, the helicity and magnetic moment of the helical structure gradually change in CrAs [1], whereas MnP shows a more complicated phase diagram [2]. Most importantly, we found that both materials show helical structure in the vicinity of the superconducting phase, although the directions of the propagation vectors are different. We also studied the chemical pressure effect on static and dynamic magnetic properties in CrAs [1]. The results suggest a coupling between the magnetism and the superconductivity.

[1] M. Matsuda et al., submitted to PRX.
[2] M. Matsuda et al., Phys. Rev. B 93, 100405(R) (2016).

Speaker: Dr. Christian Veillet, Large Binocula Telescope Observatory (LBTO)
Subject: The Large Binocular Telescope Observatory

With its two 8.4m mirrors on a common mount that can be combined to form an interferometer with a baseline of 23m, complemented with adaptive secondary mirrors, the Large Binocular Telescope provides unprecedented ground-based resolution at near- and mid-infrared wavelengths. With a suite of state of the art instruments nearing completion, the observatory is moving to full operation while adding new capabilities such as ground-layer AO and new AO-fed instrumentation. We will explore the various fields in which LBT has already contributed and stress the importance of the years to come for bringing to fruition the investment made by the LBT partners (UMN is one of theme!) and place LBT as the forerunner of the next generation telescopes scheduled to see first light in the mid-2020s.

Faculty Host: Charles E. Woodward
3:35 pm:
Speaker: Richard Samuels, Department of Philosophy, The Ohio State University
Subject: "How to Acquire Number Concepts: A New Puzzle (With Stewart Shapiro and Eric Snyder)"
Refreshments served at 3:15 p.m.

Philosophers and psychologists have long been interested in how human beings learn mathematical concepts in general, and natural number concepts, in particular. Efforts to explain how such concepts are learned, however, have resulted in a number of puzzles and problems, which have led some to conclude that these concepts cannot be learned. In this talk, we first sketch some of the more important of these puzzles, and then articulate a new one that rests upon an apparent tension between two of the best empirical probes into our natural number concepts – linguistic semantics and developmental psychology. On the face of it, the dominant views in these respective fields are in tension with each other, so that if the semanticists are right, then our best accounts of how natural number concepts are learned must be wrong. Having set out this puzzle in some detail, we argue that a structuralist conception of the naturals offers a partial resolution of this apparent tension.

3:35 pm:
Speaker: Dr. Sashank Varma, Department of Educational Psychology, University of Minnesota
Subject: How We Understand Mathematics

Mathematicians, logicians, and philosophers have contemplated for millennia the question of how people understand mathematics – of how its concepts can be both abstract and unreasonably effective for describing the physical world and engineering it to our purposes. Over a much shorter time scale – the last 50 years or so – psychologists and neuroscientists have begun taking a naturalized approach to this question, regarding mathematics as a phenomenon to be explained using the scientific method. This research has revealed how people understand fundamental numerical and arithmetical concepts, the neural correlates of this understanding, and its remarkable conservation across evolution and development. And increasingly, this research is revealing the mental mechanisms that support understanding of advanced, abstract concepts from number theory, geometry, and topology. In this talk, I review some of this research, including my own work. I also connect these scientific efforts to earlier, more introspective efforts to understand the nature of mathematics.

4:40 pm:
Please note: Carolyn Bishoff's workshop rescheduled to next week

Monday, April 30th 2018
12:15 pm:
Speaker:  Andre Luiz De Gouvea, Northwestern
Subject: Chiral Dark Sectors, Neutrino Masses, and Dark Matter

The Physics behind nonzero neutrino masses and the nature of the so-called dark matter remain elusive. Both, however, point to new degrees of freedom that couple very weakly to the known Standard Model degrees of freedom. I explore the possibility that these new degrees of freedom are the matter particles of a new chiral gauge symmetry under which the Standard Model degrees of freedom are gauge singlets. In more detail, I discuss on mechanism for constructing chiral gauge theories and present two concrete models: one based on a U(1) chiral gauge theory, the other on an SU(3)xSU(2) chiral gauge theory.

Faculty Host: M. Claudia Scarlata
4:40 pm:
Speaker: David-Michael Poehlmann
Faculty Host: Paul Crowell

Tuesday, May 1st 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.

Wednesday, May 2nd 2018
Speaker: Michael Krohn, University of Colorado
Subject: Utilizing Boosted Higgs Bosons at CMS

Thursday, May 3rd 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Ibrahim Cisse, Department of Physics, Massachusetts Institute of Technology
Subject: Super-resolution imaging of transcription in living mammalian cells

Protein clustering is a hallmark of genome regulation in mammalian cells. However, these clusters often emerge from weak or transient interactions between component biomolecules at length scales and with temporal dynamics not readily attained in live cell imaging. My lab focuses on pushing single molecule and super-resolution techniques to enable the detection and characterization of weak or transient biomolecular assemblies with very high spatial and temporal resolutions directly in living mammalian cells. We discovered that very transient clusters of RNA Polymerase II (Pol II) correlate with mRNA synthesis at gene loci. For endogenous β-actin genes in live mouse embryonic fibroblasts, we observe that short-lived (~8 s) Pol II clusters correlate with basal mRNA output. During serum stimulation, a stereotyped increase in Pol II cluster lifetime correlates with a proportionate increase in the number of mRNAs synthesized. Our findings suggest that transient clustering of Pol II may constitute a pre-transcriptional regulatory event that predictably modulates nascent mRNA output.

10:10 am:
Speaker: Ryan Schmitz
Subject: A Computational Evaluation of Neutron and Photon Detection in Plastic Scintillators
Faculty Host: Paul Crowell
Speaker: Jamie Cheshire and Pat Kelly
3:35 pm:
Speaker: Jeffrey Bub, Maryland
Subject: Discussions Over a Beer: Bohr, Einstein, Bell, and all that
Student awards will be distributed at the beginning of the Colloquium.

The Bohr-Einstein debate about the foundations of quantum mechanics is something physicists tend to think of as the sort of thing you might discuss over a beer after you’ve spent the day doing real physics. Following John Bell’s seminal 1964 paper on nonlocality, there’s a new game in town influenced by developments in quantum information. I’ll discuss the significance of this new wave in quantum foundations for the dispute that separated Bohr and Einstein. (Bring your own beer.)

Faculty Host: Michel Janssen

Friday, May 4th 2018
09:00 am:
Friday, May 4 - Sunday, May 6 2018

9:00 AM - Yingfei Gu (Harvard University): Pedagogical Presentation: Introduction to Out-of-Time-Order Correlation Functions
10:30 AM - Jacobus (Jack) Verbaarschot (Stony Brook University): Spectral Properties of the SYK Model
11:10 AM - Vladimir Rosenhaus (University of California, Santa Barbara): All-Point Correlation Functions in SYK
11:50 AM - Dmitry Bagrets (University of Cologne): Quantum Ergodicity in the SYK Model
2:00 PM - Leon Balents (University of California, Santa Barbara): A Strongly Correlated Metal Built from SYK Models
2:40 PM - John McGreeby (University of California, San Diego): Strange Metals from Local Quantum Chaos
4:00 PM - Cenke Xu (University of California, Santa Barbara): A Candidate Theory for the "Strange Metal" Phase at Finite Energy Window
4:40 PM - Subir Sachdev (Harvard University): Z2 Fractionalized Phases of a Solvable, Disordered, t-J Model

Faculty Host: Alex Kamenev
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be no seminar this week.
12:20 pm:
Speaker: Gino Graziano, University of Minnesota
Subject: Towards Microwave Studies of Josephson Junctions Based on InAs Quantum Wells with an Epitaxial Superconductor

Two-dimensional electron gases (2DEGs) with strong spin-orbit coupling are expected to host topological states in the presence of superconductivity and broken time-reversal symmetry. Josephson junctions based on such 2DEGs are predicted to exhibit an unconventional current-phase relation, characterized by a component at twice the Josephson frequency due to the presence of gapless topological Andreev bound states. In order to study the current-phase relation of these bound states, progress towards characterization of the microwave response of Josephson junctions based on InAs quantum wells proximitized with epitaxial Al.

Speaker: Yanou Cui (U. California, Riverside)
Subject: Cosmic Archaeology with Gravitational Waves from Cosmic Strings

Cosmic strings are generic cosmological predictions of many extensions
of the Standard Model of particle physics, such as a U(1)- symmetry breaking phase transition in the early universe or remnants of superstring theory. Unlike other topological defects, cosmic strings can reach a scaling regime that maintains a small fixed fraction of the total energy density of the universe from a very early epoch until today. If present, they will oscillate and generate gravitational waves with a frequency spectrum that imprints the dominant sources of total cosmic energy density throughout the history of the universe. In this talk I will demonstrate that current and future gravitational wave detectors, such as LIGO and LISA, could be capable of measuring the frequency spectrum of gravitational waves from cosmic strings and discerning the energy composition of the universe at times well before primordial nucleosynthesis and the cosmic microwave background where standard cosmology has yet to be tested. This work establishes a benchmark case that gravitational waves may provide an unprecedented, powerful tool for probing the evolutionary history of the very early universe.

Speaker: Dr. Silvia Protopapa, U. Maryland
Subject: Probing the Formation and Evolution of the Solar System Through Compositional Analysis

Over the past decade, the synergy of ground- and space-based observations, modeling efforts, and laboratory studies has highlighted vital information on the composition of solar system bodies. I will discuss some of the latest results from New Horizons at Pluto and contrast them with emerging trends seen in other trans-Neptunian objects and comets – the primitive remnants of the planetesimal disk from which the outer planets formed. I will demonstrate how characterizing the composition of these objects, which requires performing laboratory measurements and applying advanced modeling techniques to interpret state-of-the-art ground- and space-based observational data, improves our understanding of the primordial solar nebula and the accretion processes that led to the formation of the planets. I will also outline future work and perspectives in light of recent results.

Faculty Host: Charles E. Woodward
3:35 pm:
There will be no colloquium this week.
3:35 pm:
No seminar; Practice presentation
4:40 pm:
Speaker: Carolyn Bishoff, Physics, Astronomy and Earth Sciences Librarian
Subject: Workshop on data management

Saturday, May 5th 2018
09:00 am:
Friday, May 4 - Sunday, May 6 2018

9:00 AM - Johanna Erdmenger (University of Wuerzburg): Pedagogical Presentation: Introduction to Gauge/Gravity Duality
10:30 AM - Herman Verlinde (Princeton University): On the Geometry of the Firewall: Partially Entangled States in SYK
11:10 AM - Antal Jevicki (Brown University): Space-Time in the Sachdev-Ye-Kitaev Model
11:50 AM - Juan Maldacena (Institute for Advanced Study, Princeton University): Eternal Traversable Wormholes
2:00 PM - Erez Berg (University of Chicago): Solvable Models for Non-Quasiparticle Transport
2:40 PM - Ehud Altman (University of California, Berkeley): Computing Quantum Thermalization Dynamics: From Quantum Chaos to Emergent
3:50 PM - Gabor Sarosi (University of Pennsylvania): The Boundary Dual of the Bulk Symplectic Structure
4:30 PM - Shinsei Ryu (University of Chicago): Sine-Square Deformation of Conformal Field Theory
5:10 PM - POSTER SESSION

Faculty Host: Alex Kamenev

Sunday, May 6th 2018
08:00 am:
Friday, May 4 - Sunday, May 6 2018

9:00 AM - Erez Berg (University of Chicago): Pedagogical Presentation: Scrambling, SYK, and Condensed Matter
10:00 AM - Yingfei Gu (Harvard University): Entanglement in the SYK Models
11:00 AM - Andreas Ludwig (University of California, Santa Barbara): Entanglement Spectra of Symmetry Protected Topological (SPT) Phases and Boundary Conformal Field Theory
11:40 AM - Johanna Erdmenger (University of Wuerzburg): Holographic Kondo Models
12:20 PM - Julian Sonner (Universite de Geneve): Thermalisation and Black Holes in Low-Dimensional AdS/CFT
1:00 pm - Workshop ends. Thank you for your participation!

Faculty Host: Alex Kamenev

Monday, May 7th 2018
08:00 am:
12:15 pm:
There will be no seminar this week.

Tuesday, May 8th 2018
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.

Wednesday, May 9th 2018
1:30 pm:
There will be no seminar this week.
There will be no seminar this week.

Thursday, May 10th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker:  Hyun Youk, Kavli Institute of Nanoscience, TU Delft, Netherlands
Subject: Restarting life on demand: Distinguishing dormancy from death by resuming life in yeast

Stopping life indefinitely and then resuming it at the press of a button is an idea that has captivated movie makers, science fiction writers, and the general public. An open question is whether one can indeed completely stop and then resume, after many years, the life of any animals, including humans. Yeast spores are ideal for investigating the halting and resuming of cellular life. Yeast spores do not outwardly appear to be living – they neither move nor divide, exist without any external energy sources, and are believed to maintain faint, if any, intracellular dynamics. While we know how yeasts form spores when they are starved of nutrients and how a newly introduced energy source (glucose) “wakes-up” the spores and cause them to re-enter replicative life, little is known about the processes that occur, if any, inside the spores during dormancy before glucose is added, how long the dormancy can last (and what determines this timeline), and why some spores cannot wake up (thus considered dead) after a long enough time without any nutrients. We explored these questions by investigating how glucose, the necessary energy source, germinates yeast spores (i.e., restart cell replication). In doing so, we discovered that spores that are conventionally thought to be dead are, in fact, merely dormant. We found that not all spores germinate despite encountering abundant glucose. These un-germinated spores are primed so that they germinate faster upon encountering more glucose. Surprisingly, inducing expression of a useless gene that neither aids nor interferes cell growth, in dormant spores promotes germination. Crucially, we quantify an intrinsic ability by dormant spores to express genes – an intrinsic gene-expression rate. By tuning this, we could tune the probability that a spore germinates and even allow spores that glucose could not germinate, to germinate. Finally, we show that causing spores to use their stored resources to make useless proteins, while dormant, dramatically lengthens by months the time that spores escape death by months. We explain these observations with a simple mathematical model. These results provide quantitative insights into differences between death and dormancy.
______________________________________

Faculty Host: Elias Puchner
3:35 pm:
There will be no colloquium this week.

Friday, May 11th 2018
10:10 am:
Nuclear Physics Seminar in Tate 201-20
There will be no seminar this week.
12:20 pm:
There will be no seminar this week.
1:00 pm:
Thesis Defense in 301-20 Tate
Speaker: Anthony Young
Subject: Post-merger configurations of gravitationally bound dark matter systems
This is the public portion of Mr. Young's thesis defense. His advisor is Liliya Williams.
There will be no colloquium this week
3:35 pm:
There will be no colloquium this week.
3:35 pm:
There will be no seminar this week.
4:40 pm:
There will be no seminar this week.

Tuesday, May 15th 2018
11:00 am:
Speaker: Yuan Li, Peking University
Subject:  Topological Spin Excitations in a Highly Interconnected 3D Spin Lattice

The recent discovery of topological semimetals, which possess distinct electron-band crossing with non-trivial topological characteristics, has stimulated intense research interest. By extending the notion of symmetry-protected band crossing into one of the simplest magnetic groups, namely by including the symmetry of time-reversal followed by space-inversion, we predict the existence of topological magnon-band crossing in three-dimensional (3D) antiferromagnets. The crossing takes on the forms of Dirac points and nodal lines, in the presence and absence, respectively, of the conservation of the total spin along the ordered moments. In a concrete example of a Heisenberg spin model for a “spin-web” compound, we theoretically demonstrate the presence of Dirac magnons over a wide parameter range using the linear spin-wave approximation, and obtain the corresponding topological surface states [1].

Inelastic neutron scattering experiments have then been carried out to detect the bulk magnon-band crossing in a single-crystal sample. The highly interconnected nature of the spin lattice suppresses quantum fluctuations and facilitates our experimental observation, leading to remarkably clean experimental data and very good agreement with spin-wave calculations. The predicted topological band crossing is confirmed [2].

[1] K. Li et al., PRL 119, 247202 (2017).
[2] W. Yao et al., arXiv:1711.00632.

Faculty Host: Martin Greven
1:00 pm:
Thesis Defense in Tate-301-20
Speaker: Michael Janas, University of Minnesota
Subject: Applications of Semiclassical Theory in Statistical and Quantum Mechanics
This is the public portion of Mr. Janas' thesis defense. His advisor is Alex Kamenev.

Since the initiation of quantum theory in the early 20th century, semiclassical methods have been a perenniel source of insight into a diverse range of phenomena. In spite of this history, however, there remain interesting and insightful applications of semiclassical theory to physics. This thesis advances this programme in several directions. First, we consider the statistical mechanics of multivalent 1D Coulomb gases and demonstrate how the semiclassical WKB method may be used to expose its thermodynamic properties. In doing so, we develop ideas from algebraic topology and complex Riemann surfaces. Moving to quantum theory proper, these tools are applied fruitfully to the phenomenon of spin tunneling oscillations in magnetic molecules with large instrinsic spin. Moving away from the WKB approximation, these ideas from complex analysis also proved crucial in exposing universal finite-size scaling effects in 1D lattice systems such as the Su-Schrieffer-Heeger model of polyacetylene and the Kitaev chain. The thesis closes by considering the the weak noise theory of the KPZ equation and thereby discover a novel phase transition in its large deviation statistics. This last chapter will be the topic of the public portion of the thesis defense.

Wednesday, May 16th 2018
09:00 am:
US CMS 2018 Collaboration Meeting in John T. Tate Hall
May 16-19, 2018
Faculty Host: Roger Rusack
09:00 am:
Wednesday, May 16 - Saturday, May 19 2018

8:45 AM Registration
8:55 AM Opening Remarks
PNICTIDES I
9:00 AM Takasada Shibauchi (Tokyo University): Unusual BCS-BEC crossover in Fe(Se,S) superconductors
9:30 AM Sergey Borisenko (Leibniz Institute for Solid State and Materials Research (IFW) Dresden): Electronic structure and 3D gap functions of iron-based superconductors
10:00 AM Matthew Watson(University of St. Andrews): Nematic order and the superconducting gap in FeSe
10:30 AM COFFEE BREAK
10:50 AM Brian Andersen(Kobenhavns Universitet):Orbital selective quasi-particle interference and Cooper pairing in FeSe
11:20 AM Jian Kang (Florida State University): Interplay between superconductivity and nematicity in iron-based superconductors
11:50 AM Luca DeMidici (ESPCI, Paris): Hund’s correlated metals
TOPOLOGY
12:20 PM Dung-Hai Lee(University of California, Berkeley): Does vortex Majorana zero mode imply topological non-trivial superconductivity?
12:50 PM LUNCH BREAK

2:10 PM Neven Barisic (Vienna University of Technology):A fresh view of the unusual properties of the cuprates
CUPRATES 1
2:40 PM Ivan Bozovic (Brookhaven National Laboratory): What is really extraordinary in cuprate superconductors?
3:10 PM Subir Sachdev (Harvard University):SYK gauge theories
3:40 PM COFFEE BREAK
4:00 PM Louis Taillefer (Universite de Sherbrooke): The Quantum Critical Point of Cuprate Superconductors
4:30 PM Yuji Matsuda (Kyoto Univeristy): Thermodynamic evidence for a nematic phase transition at the onset of pseudogap in YBCO and Hg1201
5:00 PM Nigel Hussey (Radboud University): A Tale of Two Metals: contrasting criticalities in the cuprates and pnictides
5:30 PM RECEPTION AND POSTER SESSION

Faculty Host: Andrey Chubukov

Thursday, May 17th 2018
09:00 am:
US CMS 2018 Collaboration Meeting in John T. Tate Hall
May 16-19, 2018
Faculty Host: Roger Rusack
09:00 am:
Wednesday, May 16 - Saturday, May 19 2018

9:00 AM - Girsh Blumberg (Rutgers University): Nematicity and superconductivity in multi-band Fe-based superconductors
9:30 AM - Avraham Klein (FTPI, University of Minnesota): Identifying Mechanisms of Quantum Nematic Transitions from the Dynamic Susceptibility
10:00 AM - Pengcheng Dai (Rice University): Local orthorhombic lattice distortions in the paramagentic tetragonal phase of superconducting NaFe_{1-x} Ni_x As
10:30 AM - Coffee Break
11:00 AM - Chris Homes (Brookhaven National Laboratory): Optical Effects in Multiband Conductors and Superconductors
11:30 AM - Joseph Orenstein (University of California, Berkeley): Optical Probes of Symmetry Breaking in Magnetic and Superconducting BaFe2(As1-xPx)2
12:00 PM - Gabriel Kotliar (Rutgers University) TBA
12:30 PM - Lunch Break
2:00 PM - Jean-Marc Triscone (University of Geneva): Confinement and Superconductivity at the LaAIO3/SrTiO3 Interface and Related Systems
2:30 PM - Susanne Stemmer (University of California, Santa Barbara): Carrier Density Control of Magnetism and Hall Effects in Doped EuTiO3 Films
3:00 PM - Han Fu (University of Chicago): Anomalous Transport Properties of SrTiO3 Accumulation Layers
3:30 PM - Coffee Break
4:00 PM - Willem Rischau (University of Geneva): Superconductivity and Ferroelectricity in Strontium Titanate
4:30 PM - James Rondinelli (Northwestern University): Interplay of Correlation, Local Structure, and Inversion Symmetry in Noncentrosymmetric Metals
5:00 PM - Vlad Pribiag (University of Minnesota): Magnetism and Superconductivity in SrTiO3-based Heterostructures
5:30 PM - Maria Navarro Gastiasoro (FTPI, University of Minnesota): Normal and superconducting states of SrTiO3

Faculty Host: Andrey Chubukov

Friday, May 18th 2018
09:00 am:
US CMS 2018 Collaboration Meeting in John T. Tate Hall
May 16-19, 2018
Faculty Host: Roger Rusack
09:00 am:
Wednesday, May 16 - Saturday, May 19 2018

9:00 AM - Christian Batista (University of Tennessee, Knoxville): Dynamical Structure Factor of the Triangular Heisenberg Model
9:30 AM - Collin L. Broholm (Johns Hopkins): The Quest for a Quantum Spin Liquid
10:00 AM - Yuan Li (Peking University): Spin-orbit coupling and gapped magnetic excitations in iron-based superconductors
10:30 AM - Coffee Break
11:00 AM - Senthil Todadri (Massachusetts Institute of Technology): Origin of Mott Insulator and Superconductivity in Twisted Graphene Bilayers
11:30 AM - Oscar Vafek (National High Magnetic Field Laboratory): Superconductivity on the Brink of Spin-Charge Order in Doped Honeycomb Bilayer
12:00 PM - Liang Fu (Massachusetts Institute of Technology): Metal-Insulator Transition and Superconductivity in Graphene Superlattices
12:30 PM - Lunch Break
2:00 PM - Chandra Varma (University of California - Riverside) Topological Fluctuations in 2D-dissipative quantum XY Model: Linear in T and linear in H resistivity and other strange metal properties
2:30 PM - Riccardo Comin (Massachusetts Institute of Technology): Resonant X-Ray Studies of Electronic Orders in Quantum Solids
3:00 PM - John Tranquada (Brookhaven National Laboratory): Evidence Against an Antiferromagnetic Quantum Critical Point in La(2-x)Sr(x)CuO(4)
3:30 PM - Coffee Break
4:00 PM - Claudio Giannetti(Universita Cattolica del Sacro Cuore): Ultrafast orbital manipulation and Mott physics in multi-band correlated materials
4:30 PM - Peter Littlewood (University of Chicago): TBA
5:00 PM - Damjan Pelc (University of Minnesota): Nonlinear Response in Unconventional Superconductors

Faculty Host: Andrey Chubukov
1:00 pm:
Thesis Defense in 110 PAN
Speaker: Li He, University of Minnesota
Subject: Exploiting the spin of photons and electrons in light-matter interaction
This is the public portion of Mr. He's Thesis Defense. His advisor is Mo Li.

In light-matter interaction, the conservation of angular momentum requires the angular momentum transfer either between light and matter or within various thermodynamic reservoirs of materials, which consequently gives rise to a plethora of intriguing phenomena such as mechanical motion, charge current and magnetization. This dissertation focuses on the roles of photon spin and electron spin in light-matter interaction. The angular momentum transfer in three different scenarios are studied.First, we present the measurement of spin angular momentum of light propagating in a silicon waveguide. The continuous evolution of light polarization along propagation results in the exchange of angular momentum between light and medium and thus an optical torque to twist the waveguide. We demonstrate the use of optical torque to excite the torsional motion of an on-chip optomechanical device, which enables the coupling between optical and mechanical degrees of freedom. Second, we show the optical manipulation of surface electrons in 3D topological insulator Bi2Se3 using circularly polarized light. The transfer of angular momentum manifests itself in the spin-dependent optical selection rules and the generation of helicity-dependent photocurrent at zero bias voltage. Finally, we present the all-optical manipulation of magnetic order in ferrimagnetic alloy GdFeCo using sub-picosecond laser pulses as the ultrafast stimuli. The instantaneous heating of the electron temperature due to light absorption triggers the energy and angular momentum exchange among electron, spin and lattice reservoirs and leads to the switching of magnetization. As a step towards device application, we demonstrate an magnetic tunnel junction that can be switched all-optically without any external magnetic fields.

3:35 pm:
Thesis Defense in 129 Amundson
Speaker: Taher Ghasimakbari, University of Minnesota
Subject: Simulation Studies of Correlations, Dynamics and Phase Transitions in Diblock Copolymer Melts
This is the public portion of Mr. Ghasimakbari's thesis defense. His advisor is Prof. David Morse.

Saturday, May 19th 2018
09:00 am:
US CMS 2018 Collaboration Meeting in John T. Tate Hall
May 16-19, 2018
Faculty Host: Roger Rusack
09:00 am:
Wednesday, May 16 - Saturday, May 19 2018

9:00 AM - Erez Berg (University of Chicago): Quantum Critical Metals
9:30 AM - Emanuel Gull (University of Michigan): Charge Order in the Extended Hubbard Model
10:00 AM - Steven Kivelson (Stanford University): Superconductivity at Intermediate Coupling
11:00 AM - Sung-Sik Lee (Perimeter Institute): Kondo Effect in the Antiferromagnetic Quantum Critical Metal
11:30 AM - Artem Abanov (Texas A&M Univeristy): Non-BCS Superconductivity Near a Quantum-Critical Point
12:00 PM - Yuxuan Wang (University of Illinois): Second-Order Topological Superconductors

Faculty Host: Andrey Chubukov

Monday, May 21st 2018
11:00 am:
Thesis Defense in PAN 110
Speaker: Hannah Rogers, University of Minnesota
Subject: Effective Field Theory Analysis and Active Neutron Veto Design for the Cryogenic Dark Matter Search.
This is the public portion of Ms. Roger's Thesis Defense. Her advisor is Vuk Mandic.

Wednesday, May 23rd 2018

Thursday, May 24th 2018
3:30 pm:
Speaker: Professor Ian Mann, University of Alberta
Subject: “On the role of fast inwards and outwards ULF wave radial diffusion in shaping radiation belt morphology “

Monday, May 28th 2018
08:00 am:

Friday, June 8th 2018
08:00 am:

Monday, June 11th 2018
08:00 am:
09:00 am:

Friday, June 22nd 2018
8:30 pm:
Universe in the Park in Cedar Creek Ecosystem Science Reserve

Events are scheduled Fridays and Saturdays (rain or shine), usually beginning in June and ending mid-August. Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing.

Cedar Creek Ecosystem website

Friday, June 29th 2018
3:00 pm:
Thesis Defense in PAN 110
Speaker: Ilana Percher, University of Minnesota
Subject: 2D Mott Hopping of Vortices in an Amorphous Indium Oxide Film
This is the public portion of Ms. Percher's Thesis Defense. Her adviser is Allen Goldman

Saturday, June 30th 2018
8:30 pm:
Universe in the Park in Lowry Nature Center

Events are scheduled Fridays and Saturdays (rain or shine), usually beginning in June and ending mid-August. Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing.

Lowry Nature Center

Sunday, July 1st 2018
11:00 am:
Thesis Defense in Tate 201-20
Speaker: Vihang Mehta
Subject: Studying the building blocks of the Universe: Star-formation in low mass galaxies
This is the public portion of Vihang's PhD defense

Wednesday, July 4th 2018

Thursday, July 5th 2018
10:00 am:
Thesis Defense in PAN 110
Speaker: Jie Yang, University of Minnesota
Subject: Development and Validation of a Physics Problem Difficulty Measure
This is the public portion of Ms. Yang's thesis defense. Her Adviser is Ken Heller.
2:00 pm:
Thesis Defense in 110 PAN
Speaker: Yang Tang, University of Minnesota
Subject: Neutron Scattering Study of the Cuprate Superconductor HgBa_2CuO_{4+\delta}'
This is the public portion of Mr. Tang's thesis defense. His advisor is Martin Greven.

Saturday, July 7th 2018
8:30 pm:
Universe in the Park in William O'Brien State Park

Events are scheduled Fridays and Saturdays (rain or shine), usually beginning in June and ending mid-August. Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing.

William O'Brien State Park

Thursday, July 12th 2018
1:00 pm:
Thesis Defense in Tate 201-20
Speaker: Michael Gordon, University of Minnesota
Subject: Massive Stars: An Infrared Exploration Across the HR Diagram
This is the public portion of Michael's PhD defense

Saturday, July 14th 2018
8:30 pm:
Universe in the Park in Afton State Park

Events are scheduled Fridays and Saturdays (rain or shine), usually beginning in June and ending mid-August. Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing.

Afton State Park

Friday, July 20th 2018
8:00 pm:
Minnesota Sky-lights in Southwest sky
Jupiter just below the Moon

Friday, July 27th 2018
8:30 pm:
Universe in the Park in Dodge Nature Center

Events are scheduled Fridays and Saturdays (rain or shine), usually beginning in June and ending mid-August. Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing.

Dodge Nature Center

Saturday, July 28th 2018
8:30 pm:
Universe in the Park in Lowry Nature Center

Events are scheduled Fridays and Saturdays (rain or shine), usually beginning in June and ending mid-August. Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing.

Lowry Nature Center

Wednesday, August 1st 2018
11:00 am:
Speaker: Vihang Mehta
Subject: This is the public portion of Vihang's PhD defense.

Friday, August 3rd 2018
1:30 pm:
Speaker: Ming Li
This is the public portion of Ming's PhD defense

Saturday, August 4th 2018
1:25 pm:
Organizational meeting in Tate 301-20
8:30 pm:
Universe in the Park in Afton State Park

Events are scheduled Fridays and Saturdays (rain or shine), usually beginning in June and ending mid-August. Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing.

Afton State Park

Monday, August 6th 2018
11:00 am:
Thesis Defense in PAN 110
Speaker: Vladimir Bychkov, University of Minnesota
Subject: Escaping Events at the NOvA Far Detector
This is the public portion of Mr. Bychkov's thesis defense. His advisor is Gregory Pawloski.

Tuesday, August 7th 2018
11:00 am:
Thesis Defense in 201-20 Tate
Speaker: Micaela Bagley, University of Minnesota
Subject: Reionization from Z to A: Lessons from z~6-7 Lyman-alpha emitters and local analogs of high-redshift galaxies
This is the public portion of Ms. Bagley's PhD defense. Her Advisor is Claudia Scarlata.

Wednesday, August 8th 2018
09:00 am:
Presentations from 9-3

Thursday, August 9th 2018
12:00 pm:
REU Poster Session in PAN 110
Poster session with pizza.

Friday, August 10th 2018
8:30 pm:
Universe in the Park in Lake Maria State Park

Events are scheduled Fridays and Saturdays (rain or shine), usually beginning in June and ending mid-August. Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing.

Lake Maria State Park

Saturday, August 11th 2018
8:30 pm:
Universe in the Park in William O'Brien State Park

Events are scheduled Fridays and Saturdays (rain or shine), usually beginning in June and ending mid-August. Presentations typically run from 8:30 to 10:00 or 11:00pm, including telescope observing.

William O'Brien State Park

Monday, August 20th 2018
10:00 am:
Thesis Defense in PAN 110
Speaker: D'Ann Barker
Subject: SuperCDMS Background Models for Low-Mass Dark Matter Searches
This is the public portion of Ms. Barker's Thesis Defense. Her adviser is Prisca Cushman.
5:00 pm:
Speaker: Caner Unal
This is the public portion of Mr. Unal's Thesis Defense. His adviser is Marco Peloso.

Friday, August 31st 2018
09:00 am:
Observational Cosmology Lab at the State Fair in U of M Crossroads Exhibit Building—Dan Patch Avenue and Underwood Street
9:00 a.m.- 9:00 p.m.

Professor Shaul Hanany's Observational Cosmology Lab will showcase various technologies and techniques used by EBEX, a telescope which flew around Antarctica on a helium balloon to help us understand the beginning of the Universe. These technologies and techniques include the levitating properties of superconductors as well as the polarization properties of light.

Monday, September 3rd 2018
08:00 am:

Tuesday, September 4th 2018
1:25 pm:
Speaker: Nikolaos Biniskos, Jülich Centre for Neutron Science JCNS
Subject: Structural, magnetic and electrical properties of La1-xBixMnO3+δ (δ>0) perovskite compounds
Faculty Host: Martin Greven
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Organizational meeting

Wednesday, September 5th 2018
1:25 pm:
Speaker: Nikolaos Biniskos, Jülich Centre for Neutron Science JCNS
Subject: : Inelastic neutron scattering investigations in the series Mn5-xFexSi3

The magnetocaloric cooling process is based on the magnetocaloric effect (MCE) where entropy changes of a magnetic material in an applied magnetic field are tied to adiabatic changes in temperature. An entropy transfer between crystal lattice and the magnetic spin system has to take place. A large MCE at room temperature and low magnetic field for a material with abundant and environmentally friendly elements opens the way for magnetic cooling devices. The MCE potentially occurs in any magnetic ordering process and inelastic neutron scattering (INS) that microscopically probes the magnetization dynamics is a key tool to tackle the question of the ingredients that favor large MCE.

Mn5-xFexSi3 compounds are showing a moderate MCE (2 to 4 J/kg K depending on x) at low magnetic field change from 0T to 2T, which is promising for magnetic refrigeration applications [2]. The ferromagnetic compound MnFe4Si3 has a magnetic phase transition at about 300K. The magnetic excitation spectrum of the magnetocaloric compound MnFe4Si3 has been investigated by means of polarized and unpolarized INS on single crystals. Spectra were collected in the FM phase (TC ≈ 305 K), as well as in the paramagnetic state, in order to understand the nature of the magnetism in MnFe4Si3. Spin-wave measurements at 1.5 K reveal a strong anisotropy of the magnetic exchange interactions along the (h00) and (00l) reciprocal directions of the hexagonal system, which also manifests itself in the q-dependent linewidths in the paramagnetic state. The correlation lengths indicate a short-range order, while the average linewidth is of the order of kBTC pointing to a behavior typical of many ferromagnets. In addition, the in- and out-of-plane spin fluctuations are found to be isotropic around TC and can be suppressed by a magnetic field of 2 T [3].

The parent compound Mn5Si3 undergoes two antiferromagnetic transitions at TN1=66K (AF1) and TN2=99K (AF2). Experiments with unpolarized INS in the paramagnetic (PM) state and in the AF2 and AF1 phases revealed that AF1 is characterized by sharp spin-waves, but AF2 is characterized by a diffuse signal that resembles the one of the PM state, indicating strong spin fluctuations [4]. These fluctuations may play an essential role in the MCE.

[1] O. Tegus et al., Nature 415 (2002), 150.
[2] Songlin et al., J. Alloys Compounds, 334 (2002), 249–252.
[3] N. Biniskos et al.,. Phys. Rev. B 96, 104407 (2017).
[4] N. Biniskos et al.,. Phys. Rev. Lett. 120, 257205 (2018).

Faculty Host: Martin Greven
There will be no seminar this week.
4:30 pm:
CM Journal Club in PAN 120
There will be no Journal Club this week.

Thursday, September 6th 2018
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
3:35 pm:
Speaker: Andrew Zangwill, Georgia Institute of Technology
Subject: Walter Kohn and the Creation of Density Functional Theory
Refreshments in atrium after the Colloquium.

Today's most popular method for calculating the electronic structure of atoms, molecules, liquids, solids, and plasmas makes no use of the Schrödinger equation or the many-electron wave function. Instead, it exploits a bold hypothesis: the electron density distribution completely characterizes the ground state of a many-electron system. This hypothesis was advanced in 1964-1965 by the theoretical physicist Walter Kohn and two young postdocs. This talk traces Kohn's educational trajectory (from Nazified Vienna to an internment camp in the Canadian forest to the University of Toronto to Harvard University), his professional trajectory (from applied mathematician to nuclear physicist to solid state physicist to the inventor of density functional theory), and the circumstances which led him to win a share of the 1998 Nobel Prize for Chemistry.

Faculty Host: Michel Janssen

Friday, September 7th 2018
12:20 pm:
Subject: Specific heat in strongly hole-doped Iron-based superconductors
Speaker: Andrew Zangwill, Georgia Institute of Technology
Subject: Four Facts Everyone Ought to Know About Science

In 1994, the Nobel Prize-winning theoretical physicist Philip Anderson published an article in The Daily Telegraph of London titled Four facts everyone ought to know about science." His  facts'' are not likely the ones you would choose and my talk draws on extensive biographical research to analyze his choices in detail. What scientific and personal experiences led him to his list? What do his choices say about the scientific philosophy of someone with a legitimate claim to have been the most influential physicist of the second half of the twentieth century? I discuss whether his choices were warranted in 1994 and whether the events of the subsequent twenty-five years might cause him to revise his list.

4:40 pm:
Speaker: Ke Wang, Condensed Matter
Subject: Introduction

Tuesday, September 11th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
Subject: Organizational Meeting
Note the change of time, day and room from the previous calendar announcement. This is the time slot for the seminar for the rest of the semester.
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Meg Foster
Subject: "Soviet Space Race Propaganda - Women in space and the status of women in science."

Wednesday, September 12th 2018
1:25 pm:
Speaker: Elbio Dagotto, University of Tennessee, Knoxville and Oak Ridge National Laboratory
Subject: Iron-Based High-Tc Superconductors: Brief Review and New Results in Superconducting Ladders BaFe2S3 and BaFe2Se3

The field of iron-based high critical temperature superconductors continues attracting the attention of the Condensed Matter Physics community. I will briefly review the main ideas in this field and argue that electronic correlation effects cannot be neglected [1]. For this reason, in the main portion of the presentation I will focus on recent exciting results for the two-leg ladder compounds BaFe2S3 and BaFe2Se3.These are the only members of the iron-based family that were reported to become superconducting (at high pressure) without having iron layers in its crystal structure [2]. Theory becomes more accurate in 1D and numerically exact computational results for a two-orbital Hubbard model applied to ladders, as well as chains, will be discussed [3]. They reproduce the dominant magnetic order of BaFe2S3 and BaFe2Se3, and display intriguing indications of pairing tendencies upon doping at intermediate Hubbard couplings. I will speculate that this may be explained by the existence of unexpected preformed spin-singlets in the system [4]. Recent results for the dynamical spin structure factor of ladders S(q,) will also be briefly discussed, time allowing, and compared with neutron scattering data [5]. Novel optical modes are predicted.

[1] P. Dai et al., Nat. Phys. 8, 709 (2012), and references therein.
[2] H. Takahashi et al., Nat. Mater. 14, 1008 (2015); T. Yamauchi et al., PRL 115, 246402 (2015); J.-J. Ying et al., PRB 95, 241109 (R) (2017).
[3] N. D. Patel et al., PRB 94, 075119 (2016); PRB 96, 024520 (2017).
[4] N. D. Patel et al., in preparation.
[4] J. Herbrych et al., accepted in Nat. Communications 2018.

Faculty Host: Rafael Fernandes
There will be no seminar this week.
4:40 pm:
CM Journal Club in PAN 110
Subject: Organizational Meeting

Thursday, September 13th 2018
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
Speaker: Terry Jones, University of Minnesota
3:35 pm:
Speaker: Raman Sundrum, University of Maryland College Park
Subject: Fundamental Physics and the Fifth Dimension
Refreshments in atrium after the Colloquium.

The central aspirations, successes and puzzles of Particle Physics will be reviewed against the backdrop of the twin pillars of modern physics: Relativity and Quantum Mechanics. The notion of Naturalness will be introduced as the organizing “gambling” principle behind many searches for new particles and forces beyond the current Standard Model. The interplay between deep theoretical mechanisms of naturalness, such as Extra Spacetime Dimensions and Supersymmetry, and experimental strategies at particle colliders and other facilities will be emphasized.

Faculty Host: Tony Gherghetta

Friday, September 14th 2018
12:20 pm:
Speaker: Brenda Knauber
Subject: Noise of the Noise in Amorphous Semiconductors
No seminar this week.
Speaker: Paul Woodward, University of Minnesota
Subject: 3-D Stellar Hydrodynamics of Convective Boundary Mixing and its Consequences for Stellar Evolution

Together with collaborator Falk Herwig, at the University of Victoria, in Canada, my research team has been investigating inherently 3-D processes in stellar interiors and their effects upon stellar evolution. This work has been underway in earnest since 2013. We are focusing on brief events in stars that take place over durations of days or hours, but which involve large releases of energy due to the burning of fuels pulled into convection zones from unburned layers above. I will describe the contexts of these brief events, results of our simulations of them, and explain key aspects of how we are able to simulate them at an affordable cost. Some of our very recent work on core convection in rotating massive main sequence stars will be presented, and prospects for future work on the merger of nuclear burning shells in massive stars will be discussed.

4:40 pm:
Speaker: No Speaker Due to Schedule Change
8:00 pm:
Observing Night in 510-02 Tate
Rooftop observing through our historic telescope in the dome of the John T. Tate Hall. Presentation followed by outdoor observing (weather-permitting).

MIfA graduate students Jin-Ah Kim and James Cheshire and undergraduate student Kaitlin Ehret will be there to give a short presentation and answer any questions (about the presentation, or about astronomy/astrophysics/physics/cosmology in general!), then (weather permitting) we'll head upstairs and break out the historic 122 year-old 10.5" refracting telescope in the dome and some modern reflecting telescopes on the roof of Tate Hall to look at Mars and Saturn! The current forecast calls for cloudy skies Friday night, but even if observing isn't possible we'll be there to present and chat with everyone! The presentation will be on the science of spectroscopy, which is the main technique astronomers use to figure out what objects in space are made of, and how they're moving.

Monday, September 17th 2018
12:15 pm:
Speaker: Matt Fritts, University of Minnesota
Subject: Detector R&D for SuperCDMS

SuperCDMS is a direct-detection dark matter search employing cryogenic semiconductor detectors. One focus for SuperCDMS is low-mass WIMPs that would deposit very low energies in a detector; thus the detectors are designed for low energy thresholds and high energy resolution. Recent R&D efforts have taken resolution to the limit of single electron-hole pairs produced by ionizing events. WIMP searches with low-threshold detectors depend on the ionization yield for nuclear-recoil events, which is not well known at such low energies. One attempt to measure this is based on neutron capture. If WIMPs turn out to have high masses, then high exposures become important, and larger detectors will be needed. Recently 150mm-diameter CDMS-style detectors have been made and tested. I will report on our R&D efforts in each of these areas.

Faculty Host: Vuk Mandic

Tuesday, September 18th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Benjamin Frigo Vaz , Bionanotechnology Lab, UMn
Subject: Orbital Mirrors for Terraforming Mars
4:00 pm:

Wednesday, September 19th 2018
1:25 pm:
Speaker: Ali Yazdani, Princeton University
Subject: Visualizing quantum Hall liquids and their boundary modes

In a series of experiment on 2D electron gas at the surface of Bi, we have been able to probe a number of novel features of quantum Hall liquids for the first time. First, we have been able to use the scanning tunneling microscope (STM) to directly visualize Landau orbits in real space. This new technique has been used to show that the electronic states associated with the valley state on the surface of Bi form nematic quantum Hall liquids. [1] By tuning the magnetic field, we have been able to stabilize different type nematic fluids, and have been able uncover a ferroelectric quantum Hall liquid that forms when only one of the valley get occupied.[2] We are able to demonstrate that the formation of these quantum Hall phases are driven by electron-electron interaction. Finally, in the most recent experiment, we have been able to uncover domain walls between different nematic quantum Hall states and to direct image the 1D Luttinger liquids that form at such interfaces. This new type of Luttinger liquids can become metallic or insulating depending on the number of valley-textured edge modes.[3]

[1] B. Feldman et al. Science 354 6310 (2016).
[2] Randeria et al. Nature Physics, 14 1709 (2018)
[3] Randeria et al. in preparation. (2018)

Faculty Host: Andrey Chubukov
Organizational Meeting
4:40 pm:
CM Journal Club in PAN 110
Subject: No journal club this week

We will meet on September 26th. Then the plan would be a regular meeting every other week.

Thursday, September 20th 2018
10:10 am:
Biophysics Seminar in 110 PAN
Speaker:  Prakash Kara, Professor in the Department of Neuroscience, University of Minnesota
Subject: Determining the precision of networks in the living brain with multi-photon microscopy
PLEASE NOTE THE SEMINAR IS IN ROOM PAN 110 THIS WEEK
Speaker: Trevor Knuth & Liliya Williams
Subject: To be announced
3:35 pm:
Speaker: Ali Yazdani, Princeton University
Subject: Spotting the elusive Majorana under the microscope
Refreshments in atrium after the Colloquium.

Ettore Majorana famously considered that there may be fermions in nature that are their own antiparticle — and then he mysteriously disappeared just after proposing the idea in 1938. In recent years, we have learned how to engineer materials that harbor quasiparticles that behave similar to fermions Majorana had envisioned. In particular, there has been a focus on one-dimensional topological superconductor that harbor Majorana zero modes (MZM) that can potentially be used to make fault-tolerant topological quantum computation possible. Recently, we have proposed and implemented a platform for realization of topological superconductivity and MZM in chains of magnetic atoms on the surface of a superconductor [1,2]. In this talk, I will describe this platform and the series of experiments we have performed to establish the presence of these exotic quasi-particle using spectroscopic mapping with the STM. [2-4] These include a recent study of the unique spin signature of MZM.[4] Finally, if there is time I will describe some ongoing experiment on realization of MZM in a platform based on chiral quantum spin Hall edge states.

[1] S. Nadj-Perge et al. PRB 88, 020407 (2013).
[2] S. Nadj-Perge et al. Science 346, 6209 (2014).
[3] B. E. Feldman et al. Nature Physics 13, 286 (2016).
[4] S. Jeon et al. Science 358, 772 (2017).

Friday, September 21st 2018
12:20 pm:
Speaker: Scott Dossa
Subject: Simulating Crystal Growth in an Optical Floating Zone Furnace
12:30 pm:
No seminar this week.
1:00 pm:

Vainshteinfest: Insights info Quantum Field Theory

1:00 - 1:45 pm
"Monopoles versus the instanton-dyons"
Edward Shuryak
State University of New York, Stony Brook

1:45 - 2:30 pm
"Generalized state sums and quantum distillations"
Mithat Ünsal
North Carolina State University

2:30 - 3:00 pm
Coffee break

3:00 - 3:45 pm
"Comments on the Theta term in Yang-Mills theory"
Zohar Komargodski
Weizmann Institute of Science

3:45 - 4:30 pm
Cédric Deffayet
Institut d'astrophysique de Paris

ABSTRACTS:
"Monopoles versus the instanton-dyons"
Edward Shuryak
State University of New York, Stony Brook

Abstract: Magnetic monopoles explained confinement and flux tubes, unusual kinetics of quark-gluon plasma, and, recently, even observed properties of jet quenching. But in QCD-like theories there is no classical solutions of this kind. Instantons and their constituents, the instant-dyons, lead to systematic semiclassical theory, which recently explained deconfinement and Chiral phase transitions in a variety of settings. The talk will briefly review that, and focus on the nature of the so called Poisson duality, confirming that these two languages are dual to each other, and lead to the same partition function. At the end we show what does it tell us about QCD monopoles.

"Generalized state sums and quantum distillations"
Mithat Ünsal
North Carolina State University

Abstract: I describe a generalization of the notion of partition function in general quantum field theories. The thermal partition function is a state sum over the Hilbert space, which typically has non-analyticities, and can be used to study phase transitions, and thermodynamics. I will describe graded states sums which may be controllably tuned to be analytic. As such, they can be used to interpolate between weak and strong coupling regime of QFTs. I will show that this notion is useful to understand general non-perturbative aspects of quantum field theory, providing examples from 2d QFTs, and 4d QCD.

"Comments on the Theta term in Yang-Mills theory"
Zohar Komargodski
Weizmann Institute of Science

Cédric Deffayet
Institut d'astrophysique de Paris

Abstract: I will review the "Vainshtein mechanism", first formulated in
the context of massive gravity by Arkady in 1972 and now routinely used in
various theories beyond General Relativity.

Party for Terry Thibeault, no colloquium.
3:35 pm:
Speaker: Sarah Robins , Department of Philosophy - University of Kansas
Subject: The Neurophilosophy of Memory: Reconciling Stable Engrams and Neural Dynamics
Refreshments served at 3:15 p.m.
4:40 pm:
Speaker: Martin Greven, Condensed Matter
Subject: New developments and opportunities in quantum materials research
8:00 pm:
Observing Night in 510-02 Tate
Rooftop observing through our historic telescope in the dome of the John T. Tate Hall. Presentation followed by outdoor observing (weather-permitting).

Monday, September 24th 2018
12:15 pm:
Speaker: Joshua A. Frieman, Fermilab
Subject: Probing Cosmology with the Dark Energy Survey

I will overview the Dark Energy Survey (DES) project and highlight its early science results, focusing on cosmology results from the first year of the survey. The DES collaboration built and is using the 570-megapixel Dark Energy Camera on the Blanco 4-meter telescope at NOAO's Cerro Tololo Inter-American Observatory in Chile to carry out a deep, wide-area, multi-band optical survey of several hundred million galaxies and a time-domain survey that has discovered several thousand supernovae. The survey started in Aug. 2013 and will finish early next year. DES was designed to address the questions: why is the expansion of the Universe speeding up? Is cosmic acceleration due to dark energy or does it require a modification of General Relativity? DES is addressing these questions by measuring the history of cosmic expansion and the growth of structure through multiple complementary techniques: galaxy clusters, the large-scale galaxy distribution, weak and strong gravitational lensing, and supernova distances, as well as through cross-correlation with other data sets, particularly the cosmic microwave background. I will also briefly discuss how the DES data are being used in unexpected ways, from probing dark matter with newly discovered ultra-faint dwarf galaxies to a new probe of the Hubble constant using the kilonova counterpart of a binary neutron star gravitational-wave source.

Faculty Host: Vuk Mandic
2:00 pm:
FTPI Seminar in Physics 301-20
Speaker: Alexander Monin
Subject: EFT for CFT with large charge

In a generic conformal field theory the spectrum of operators carrying a large U(1) charge can be analyzed semiclassically. The key is the operator state correspondence by which such operators are associated with a finite density superfluid phase for the theory quantized on the cylinder. The dynamics is dominated by the corresponding Goldstone hydrodynamic mode and the derivative expansion coincides with the inverse charge expansion. I will illustrate this situation by first considering simple quantum mechanical analogues and then will systematize the approach by employing the coset construction for non-linearly realized space-time symmetries. Focussing on a 3-dimensional theory I will illustrate that the three point function coefficients turn out to satisfy universal scaling laws and correlations as the charge and spin are varied. Lastly I’ll show how the approach can be generalized to the case of large spin by considering vortices in the superfluid.

Speaker: Natalia Perkins, University of Minnesota
Subject: The pursuit of Majorana fermions in Kitaev materials
Refreshments in atrium after the Colloquium.

The 1937 theoretical discovery of Majorana fermions has since impacted diverse problems ranging from neutrino physics and dark matter searches to fractional quantum Hall effect, superconductivity and quantum spin liquids (QSLs). In my talk I will focus on the hunting for Majorana fermions in Kitaev materials, which believe to harbor a variety of QSLs. These Kitaev QSLs exhibit two types of fractionalized quasiparticle excitations - itinerant Majorana fermions and gapped Z2 fluxes. In recent years, a remarkable theoretical and experimental progress has been achieved in understanding that these fractionalized quasiparticles and, in particular, Majorana fermions can be effectively probed by conventional spectroscopic techniques such as inelastic neutron scattering, Raman scattering with visible light, and resonant inelastic X-ray scattering.

Tuesday, September 25th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Rafid Mahbub, University of Minnesota
Subject: Primordial Black Hole formation in Inflation models

Primordial black holes form in the early universe when over-dense regions gravitationally collapse upon horizon reentry. While there are many proposed formation mechanisms, inflation is an attractive candidate due to curvature perturbations that are generated. Inflation models that exhibit an inflection point in their potentials are seen to give rise to enhancements in the power spectrum during horizon exit, which can produce PBHs, that are long-lived, at sufficient abundances- while also satisfying observational constraints. Lastly, if not all, a fraction of current dark matter content may be comprised of PBHs.

Wednesday, September 26th 2018
1:25 pm:
Speaker: Inna Vishik, UC Davis
Subject: ARPES studies of the model cuprate HgBa2CuO4+d (Hg1201)

The mechanism of high temperature superconductivity in cuprates is one of the biggest unsettled questions in physics, and big stumbling block in this mature field is the question of universal vs materials-dependent or technique-dependent behavior. HgBa2CuO4+ (Hg1201) is considered to be a model cuprate because it has a structurally-simple crystal structure and can have a relatively long electron mean free path, and as such, it is well-characterized by transport and scattering experiments. However, few angle-resolved photoemission spectroscopy (ARPES) experiments have been performed on this material thus far, even though this technique is instrumental in highlighting critical momentum-space anisotropies in crystalline solids. I will present recent ARPES results on Hg1201, which shed light on single-particle scattering processes and electron-boson coupling, and together with a variety of complementary probes can form a coherent experimental description of a model cuprate.

Faculty Host: Martin Greven
To be announced

Thursday, September 27th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Keehun Kim, graduate student in Sivaraj Sivaramakrishnan’s lab, Department of Genetics, Cell Biology, and Development, University of Minnesota
Subject: A cell-free FRET-based assay for profiling the intrinsic efficacy of GPCR ligands

G protein coupled receptors (GPCRs) are 7-helix transmembrane receptors which regulate diverse intracellular signaling cascades in response to extracellular stimuli. Due to their crucial role in modulating most human physiological processes, roughly 25% of the pharmaceutical in the current market target GPCRs. The intrinsic efficacy of GPCR ligands is an essential parameter in operational models that convert ligand binding to downstream response. Measurement of intrinsic efficacy of GPCR ligands has eluded researchers, given the diversity of factors that can modulate downstream signaling, including expression levels of GPCR, G protein-dependent and independent effectors, regulatory factors such GRKs, RGS, and post-translational modifications. While ligand efficacy can be directly measured from G protein activation rates, such assays either require significant amounts of purified GPCR and G protein or are limited by the heterogeneity inherent in crude membrane preparations. We have previously used FRET based SPASM sensors to measure interactions between the full-length GPCR and the C-terminus of the α5-helix of distinct Gα subunits. We have demonstrated the utility of these sensors in live cells to probe the stabilization of G protein-selective receptor conformations by distinct GPCR ligands. While the SPASM GPCR sensors robustly report ligand-dependent G protein selection, the live cell FRET measurements are limited by constraints on sensor expression levels and ligand-stimulation times. Here, we present a cell derived assay for SPASM GPCR sensors that provides highly reproducible FRET measurements with minimal sensitivity to sensor expression levels and ligand-stimulation times. Importantly, our cell-free assay provides a scalable and stable reagent for screening GPCR ligands. Our findings for the b2 adrenergic receptor show that the GPCR-Gα C-terminus interaction is sufficient to recapitulate the intrinsic efficacy as measured from G protein activation rates. Taken together, our cell-free assay provides a scalable FRET-based readout for the intrinsic efficacy of GPCR ligands, while reinforcing the structural mechanisms underlying G protein activation.

Speaker: Aliza Beverage, University of Minnesota
3:35 pm:
Physics and Astronomy Colloquium in Physics Tate B50
Speaker: Raymond Jeanloz, UC Berkeley
Subject: Pressure as a Probe for Atoms, Molecules and Planets
Refreshments in atrium after the Colloquium

Experiments using diamond anvils and the largest lasers in the world can exceed the atomic unit of pressure, profoundly changing the nature of atom structure and chemical bonding. Laboratory studies of the metallic hydrogen and helium that dominate large-planet (Jupiter, Saturn) and stellar interiors, and of new forms of ice that comprise icy giant planets (Neptune, Uranus), are complemented by experiments converting simple metals into ionic salts and taking elements to the statistical-atom (Thomas-Fermi-Dirac) regime. Interesting in their own right, and as validation of first-principles quantum simulations, these experiments also inform us about the origins and evolution of planets.

Faculty Host: Cynthia Cattell

Friday, September 28th 2018
12:20 pm:
Speaker: Shuhui Luo
Subject: Elastic transmission of a Helium beam through a slab of superfluid Helium
Subject: SYK and Conformal Field Theory
No Colloquium. Physics Colloquium speaker is a planetary physicist.
3:35 pm:
Speaker: Deirdre Cooper Owens Department of History Queens College, CUNY
Subject: Exploring Hapticity, Slavery and the Emergence of American Gynecology
Refreshments served at 3:15 p.m.

In this talk, Cooper Owens explores how enslaved women's perceptions of their senses (sights, sounds, touch, and taste), influenced their behavior and healing while they underwent gynecologic surgeries. She asserts that slavery studies and medical history sits at the center of haptic studies and in order to understand the medical lives of enslaved people, we must understand their responses to their environments and also, the new ethic of being early gynecologists created out of these encounters.

4:40 pm:
8:00 pm:
Observing Night in 510-02 Tate
Rooftop observing through our historic telescope in the dome of the John T. Tate Hall. Presentation followed by outdoor observing (weather-permitting).

Monday, October 1st 2018
12:15 pm:
Speaker: Iary Davidzon, IPAC/Caltech
Subject: Probing the early universe *without* JWST

The James Webb Space Telescope (JWST) will not be the only breakthrough for high redshift (z>~3) studies. Exquisite data are coming from Subaru and Spitzer telescopes, eventually covering a large area of the sky (~25 sq deg) at an unprecedented depth. Probing such a large cosmic volume will allow to collect a statistically significant sample of rare, massive galaxies still undetected in pencil-beam HST surveys. In this talk I present "pathfinder results" from the COSMOS field, showing the importance of rare massive objects to constrain star formation efficiency and stellar-to-halo mass relationship at z>3. In the same context, I also discuss present limitations from an observational point of view and how they affect our understanding of galaxy evolution (e.g. the so-called "Eddington bias").

Faculty Host: M. Claudia Scarlata

Tuesday, October 2nd 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Aleksey Cherman, University of Minnesota
Subject: Patricle vortex systems and the nature of cold quark matter.

It is believed that cold dense quark matter is a "color-superconducting" state of matter. What does that mean? Is this sharply different from a standard "confirmed" nuclear superfluid? I'll give a basic overview of recent progress on these formal questions, with a warm up discussion of standard electromagnetic aupercondtivity the answers to the above questions have interesting physical consequences for the quantization of angular momentum of quasiparticle excitations in dense quark matter.

1:25 pm:
Speaker: Chiara Amato, Department of Aerospace Engineering
Subject: Validation of Hypersonic Flow Simulations via Molecular-Scale Physics

Wednesday, October 3rd 2018
1:25 pm:
Edythe and Irving Misel Family Lecture Day, No Seminar this Week
4:40 pm:
CM Journal Club in PAN 110
Subject: No journal club this week

The next journal club will be on Oct 10th. We will discuss physics about resonant valence bond.

7:00 pm:
Misel Public Lecture in McNamara Alumni Center, Memorial Hall
Speaker: Professor Nergis Mavalvala, Massachusetts Institute of Technology
Subject: Gravitational Waves: A New Window to the Universe

Recent announcements of the first ever detections of gravitational waves from colliding black holes and neutron stars have launched a new era of gravitational wave astrophysics. I will describe the science, technology, and human story behind these discoveries that provide a completely new window into some of the most violent and warped events in the Universe.

Thursday, October 4th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Jon Garamella, graduate student in Vincent Noireaux’s lab, School of Physics and Astronomy, University of Minnesota
Subject: Synthetic cell prototyping using a cell-free transcription-translation system (TXTL)

Cell-free Transcription-translation (TXTL) systems can be used in synthetic cell engineering to reconstitute cellular processes and functions. The bottom-up construction of cell-sized compartments programmed with DNA that are capable of sensing their chemical and physical environment remains challenging. Here, we develop techniques to prototype synthetic cells with passive and active membrane functionality. We construct liposomes programmed to intake nutrients from the surroundings and respond to external, mechanical stimuli using alpha-hemolysin and the mechanosensitive channel of large conductance, respectively. High-throughput techniques to test the viability of membrane proteins are also described.

Speaker:  Jamie Cheshire, University of Minnesota
3:35 pm:
Speaker: Professor Nergis Mavalvala, Massachusetts Institute of Technology
Subject: Gravitational wave detectors: past, present and future
Refreshments in atrium after the Colloquium.

The Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves for the first time in 2015, and has continued to make discoveries. I will discuss the instruments that made these discoveries, the science so far, and plans for future improvements and upgrades to LIGO.

Friday, October 5th 2018
12:20 pm:
Speaker: Mengxing Ye
Subject: Quantization of the thermal Hall conductivity at small Hall angles

Recent experiments have described the measurement of a near-quantized thermal Hall conductance in α- -RuCl_3 as direct evidence for the propagation of a chiral Majorana mode in this system and consequently as smoking gun evidence for an intermediate chiral spin liquid phase in this system. In practice, however, contacts are applied to the lattice, and one must ask in detail whether the experimental setup can directly, or even at all, probe the Majorana current. Moreover, the large experimental longitudinal thermal conductivity, attributed to phonons (in the chiral phase, κxxspins = 0- ) begs for an investigation of the spin-lattice coupling, and what its role is on the quantization of the thermal Hall conductivity. We show that due to the bulk and edge mixing of energy propagation, the temperature gradient of the bulk phonons develops a transverse component which may contribute to a quantized effective thermal Hall conductance. We also discuss the situations where the quantization breaks down and predict notable experiments that test it

Speaker: Daniel Harlow (MIT)
Subject: Symmetries in Quantum Field Theory and Quantum Gravity

I describe recent work with Hirosi Ooguri using AdS/CFT to prove a series of old conjectures about symmetries in quantum gravity. Along the way I will clarify several subtleties about how global and gauge symmetries are defined in quantum field theory.

There will be no colloquium this week
3:35 pm:
Speaker: Erik Peterson, Department of History - University of Alabama
Subject: "Epigenetics is 76 years old, so why are you just now hearing about it?"
Refreshments served at 3:15 p.m.
4:40 pm:
Speaker: Patrick Kelley, MIFA

Monday, October 8th 2018
12:15 pm:
Speaker: Ali Kheirandish, UW - Madison
Subject: The first evidence for the origin of high-energy cosmic neutrinos: multimessenger observation of a flaring blazar

For the first time since the discovery of high-energy cosmic neutrinos in IceCube, a distant gamma ray blazar was identified as a high-energy neutrino source. This represents the first evidence for the origin of very high energy cosmic rays. In this talk, I will review the status of high-energy cosmic neutrino flux measurements and how a multimessenger campaign led to the identification of blazar TXS 0506+056 as the origin of a high energy neutrino. Furthermore, I will discuss how archival data searches showed that the high-energy neutrino flux from the source is dominated by a neutrino burst, which implies flaring sources strongly contribute to the cosmic ray flux. I investigate the contribution of a subclass of flaring blazars to the high-energy neutrino flux and speculate on its connection to the very high-energy cosmic ray observations.

Faculty Host: Vuk Mandic
Speaker: Fiona Burnell, University of Minnesota
Subject: The emergence of topology in strongly correlated many-body systems
Refreshments in atrium after the Colloquium.

At sufficiently low temperatures, quantum mechanics plays a key role in determining materials’ behaviours. Particularly in systems where interactions are important, this can lead to macroscopic physical properties that are fundamentally different from what we expect both from single-particle quantum mechanics, and from interacting classical systems. Among the possibilities are that two systems may locally look the same, but globally behave very differently. These global differences are described mathematically by a variety of topological quantities, which capture important physical differences such as statistical interactions between particles, and distinctive low-energy physics at the systems' boundaries. I will describe recent developments in our understanding of interacting topological phases in the presence of global symmetries, and how these are connected to the “unusual" (or, in technical terms, anomalous) properties of their low-energy boundary states.

Tuesday, October 9th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Andre Sieverding, University of Minnesota
Subject: Neutrinos in core-collapse supernova nucleosynthesis

Supernova explosions of massive stars provide an important
contribution to the chemical enrichment of the galaxy and neutrinos
and their interactions with nuclei play a crucial role in that
environment. I will give an overview of the role of neutrinos for
supernova explosions and present recent progress in nucleosynthesis
calculations for the neutrino process, that combine state-of-the art
nuclear models and astrophysical modelling.

1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: No seminar this week.

Wednesday, October 10th 2018
1:25 pm:
Speaker: Joel Moore, UC Berkeley
Subject: Unconventional hydrodynamics in 1D and 2D quantum matter

Hydrodynamical effects such as viscosity become significant In very clean materials and in ultracold atomic gases. We discuss how quantum mechanics and reduced dimensionality lead to new kinds of hydrodynamics and far-from-equilibrium transport. Examples include semiclassical kinetic theory (“generalized hydrodynamics”) and exact far-from-equilibrium results for some quantities in the XXZ model through expansion potentials. In many cases the predictions of theoretical approaches based on integrability can be checked, using in DMRG and other matrix product state algorithms. The talk finishes with a discussion of some experimental goals and challenges in 2D materials, including the possible observation of Hall viscosity in current experiments.

Faculty Host: Andrey Chubukov
Speaker: Nhan Viet Tran, FNAL
Subject: Fast & Furious 10: triggers, ML, and computing at the LHC and beyond

With increasingly complex collision environments at the LHC and concurrently growing data rates, more sophisticated detector and reconstruction methods are required to preserve the LHC program. However, this cannot coincide with an upsurge of computational and processing time. I will discuss plans for the CMS hardware trigger in the HL-LHC era and the role of advanced reconstruction techniques and the potential for machine learning implementations in the trigger FPGA hardware. Finally, I will show recent results relating this work to advances in computing which could revolutionize future high-level trigger and offline computing architectures at the LHC and other large-scale experiments like those in the neutrino program.

4:40 pm:
CM Journal Club in Tate 201
Subject: Resonant Valence Bond

Thursday, October 11th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Dushyant Mehra, graduate student in the biomedical engineering department at the Mayo Clinic
Subject: Mapping and Manipulation of DNA Architecture in Vivo

Genome organization helps regulate gene expression and is an important driver in processes associated with cell development and cell differentiation. Enhancer and insulator complexes that dynamically form play central roles in governing transcriptional dynamics of genes that are associated processes such as cell fate determination and alterations in organization can often lead to disease. Current crosslinking based methods such that map DNA conformations by measuring crosslinking frequency often don’t account for changes in chromatin architecture across different cell states. Recent research suggests that analyzing speed of DNA interaction and not just contact frequency is important in finding DNA contacts that govern gene expression and DNA contacts that important in governing gene expression may not be picked up by current crosslinking based mapping techniques. Dynamic imaging based methods have been used to track dynamics of DNA overtime but are often difficult to apply due conventional microscopy limits which makes it difficult to track dynamics of clustered enhancers and insulators. By employing CRISPR-dCas9 DNA binding domains and super resolution photo-localization microscopy, we aim to optically map chromatin architecture and track dynamics of DNA during a variety of cell states and by tethering sections of DNA together, we are able to understand how these contacts affect affects gene expression. Together, we are able to develop a toolkit to understand the role that chromatin architecture plays in transcription during different cellular processes and cell states.

Speaker: Andrew Helton (SOFIA)
Subject: Understanding the long-term variability of the dusty, symbiotic Mira variable star, R Aquarii

R Aquarii (R Aqr) is a nearby symbiotic system composed of a Mira
variable star and a hot white dwarf (WD). The pulsation period of R Aqr is
387 days. Of particular interest to us, however, is a peculiar suppression
of the pulsation amplitude that occurs on roughly 44 year timescales.
These events correlate with the periastron passage of the WD, the next of
which is expected to begin sometime prior to 2020. In this talk I will
present recent efforts to monitor and analyze the mid-IR properties of
this dusty system leading up to the next periastron passage of the WD,
with particular emphasis on mass loss and dust production.

At the end of the talk, I will give a brief update on activities at the
Stratospheric Observatory for Infrared Astronomy (SOFIA). I will discuss
some interesting recent science results, provide information on how to get
opportunities with the Observatory.

3:10 pm:
School Photo in Tate Mall Entrance
Refreshments will be served before the photo. Photo will be at 3:20 sharp on the steps.
3:35 pm:
Speaker: Joel Moore, UC Berkeley
Subject: Topology and the electromagnetic responses of quantum materials
Refreshments in atrium after the Colloquium.

This talk starts by reviewing the remarkable theoretical and experimental
progress in topological materials over the past decade. Three-dimensional
topological insulators realize a particular electromagnetic coupling known as
“axion electrodynamics”, and understanding this leads to an improved
understanding of magnetoelectricity in all materials. We then turn to how
topological Weyl and Dirac semimetals can show unique electromagnetic
responses; we argue that in linear response the main observable effect
solves an old problem via the orbital moment of Bloch electrons, and how
in nonlinear optics there should be a new quantized effect, at least approximately.

7:00 pm:
Dark Matter Detectives in John T. Tate Hall, Room B50
Speaker: Professor Priscilla Cushman
MIfA Public Lecture Series

By the 1990’s there was clear evidence that the Universe was filled with a mysterious form of matter that affected the motion of stars and galaxies, bent light from distant galaxies, and influenced cosmic evolution. While the evidence for the existence of this “dark matter” is overwhelming, its nature is still unknown.

Over the last several decades, scientists have been searching for clues, which might reveal how dark matter interacts with normal matter and why there is so much of it. Ever larger experiments have been built deep underground where cosmic rays can’t interfere, in order to capture a glimpse of the elusive dark matter particles as they stream through our solar system.

So far, there has not been a confirmed sighting in a terrestrial detector, but the dark matter detectives are not giving up. Learn about what progress has been made over the last decade and where we go from here.

Friday, October 12th 2018
12:20 pm:
Speaker: Eduardo Vitral
Subject: Curvature driven evolution of a smectic-A liquid crystal out of thermodynamic equilibrium
Speaker: Bhupal Dev (Washington U.)
Subject: New Physics at Neutrino Telescopes

The recent observation of high-energy neutrinos at the IceCube neutrino telescope has opened a new era in neutrino astrophysics. Understanding all aspects of these events is very important for both Astrophysics and Particle Physics ramifications. In this talk, I will discuss a few possible new physics scenarios, such as dark matter, leptoquarks and supersymmetry, that could be probed using the IceCube data. I will also relate this to the puzzling observation of two upgoing EeV events recently made by the ANITA experiment that were not seen by IceCube.

Speaker: Lucy Ziurys, University of Arizona
Subject: A Molecular View of the Late Stages of Stellar Evolution: Millimeter Observations of Supergiants and Planetary Nebulae

Molecular rotational lines, observed primarily at millimeter wavelengths, are unique probes of the environments around dying stars. They not only provide insight into the physics and chemistry of the stellar winds, but also can probe interior nucleosynthesis through isotopic composition. Using the millimeter/sub-mm telescopes of the Arizona Radio Observatory, we have been conducting extensive observations of molecular lines in the envelopes of supergiant/hypergiant stars, as well as in planetary nebulae. Our past work on supergiant VY Canis Majoris revealed a complex velocity structure with multiple, highly-collimated outflows, linked to known dust features. The molecular data confirm the occurrence of multiple, recent mass loss events. Our more recent study of NML Cygnus suggests a very similar mass loss scenario in the winds of this supergiant. In addition, the envelopes of both stars exhibit a unique chemistry with refractory oxides. Our very recent studies of planetary nebulae (PNe) show that these highly ionized objects are also rich in molecular material. Observations of over 20 different nebulae at various evolutionary stages reveal the presence of many polyatomic species such as HCN, HNC, CN, H2CO, CCH, and c-C3H2. Moreover, the abundances do not decrease with the age of the nebulae, and are in fact quite high in very old objects such as the Helix. These results suggest that PNe ejecta are at least partly molecular in content. Some of these nebulae also have enriched C, N, O isotopes. For example, K4-47 has 12C/13C = 2.0, 16O/17O = 21.4 and 14N/15N = 13.3, suggesting some explosive event at the end of the Asymptotic Giant Branch (AGB) phase. In addition, K4-47 appears to be contain many unidentified molecular lines – the target of laboratory spectroscopy studies that we also conduct to aid in our astrophysical interpretation.

3:35 pm:
Speaker: Susan Jones, Program in History of Science; Department of Ecology, Evolution & Behavior - University of Minnesota
Subject: "The Homelands of the Plague: Soviet Disease Ecology in Central Asia, 1920s–1950s"
Refreshments served at 3:15 p.m.

This presentation analyzes the development of an important Russian/Soviet school of "disease ecology" at the intersection of human medicine, veterinary medicine, and ecological fieldwork. Part of a larger study in progress, I will argue that (1) Russian/Soviet disease ecology arose within the development of 'frontier' settler societies and (2) although entanglements with the dynamic Soviet political system directly affected scientists' work and ideas, analysis of their local activities in the borderlands demonstrates a surprising independence and autonomy. I conclude by discussing how collaboration between graduate students in the history of science, technology, and medicine, scientists, and informants in Kazakhstan have been essential to this historical project.

4:40 pm:
Speaker: Aleksey Cherman, High Energy

Monday, October 15th 2018
12:15 pm:
Speaker: Chris Pankow, Northwestern
Subject: Gravitational-wave Astrophysics with Compact Binary Mergers

The past three years have encompassed a meteoric rise of gravitational-wave astronomy with the activation of second generation gravitational-wave interferometers and the subsequent direct detection of GW150914 --- a gravitational-wave transient from a merging binary black hole. To date, two observing runs have been conducted, the second of which inaugurated a three instrument, worldwide network. I will report the key results driving the birth and growth of gravitational-wave astronomy: stellar mass black hole binaries and their measured masses and spins, the implications for compact binary astrophysics, and the foundation for future population studies. August of 2017 also added a highly anticipated component to multi-messenger astronomy. GW170817, the first binary neutron star detected with gravitational waves, kicked off a monumental joint electromagnetic and gravitational-wave observational campaign --- I will highlight ongoing studies of this watershed event. Finally, I will review the progression towards a more sensitive gravitational-wave network of up to five interferometers and prospects for compact binary detection in the next few years.

Faculty Host: Vuk Mandic
3:35 pm:
Speaker: Andre David, CERN Switzerland.
Subject: Fundamentals of Science and Fundamental Science

We'll discuss fundamentals of science as applied to fundamental science in high-energy particle physics at the LHC. After a stroll through the garden of the LHC's main accomplishment, we'll wander through a dark forest of what is beyond until we make out the light from the prairie of high-precision.”

Tuesday, October 16th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Aleksey Cherman, University of Minnesota
Subject: Effective actions for topologically-enriched superfluids

Cold dense quark matter is a superfluid, but not quite the
"topologically-enriched" superfluid. I'll explain how to derive a
local effective action for this gapless phase of matter, which
involves coupling the superfluid to a topological quantum field theory
(TQFT). Along the way we'll talk about continuum "BF" actions for
four-dimensional discrete gauge theories, as well certain peculiar
five-dimensional cousins of these TQFTs relevant for our superfluids.
This talk is a more technical follow-up to a talk from two weeks ago,
but will be aimed to be followable by people who didn't attend the
first talk.

1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: John Wygant

Wednesday, October 17th 2018
1:25 pm:
Speaker: Raymond Osborn,Materials Science Division, Argonne National Laboratory
Subject: Imaging Nanoscale Disorder in Reciprocal Space

Correlated defects are responsible for the functional properties of many materials that underpin energy-related technologies. Single-crystal diffuse scattering using x-rays or neutrons is a powerful probe of short-range order in crystalline lattices, but its use has been limited by the experimental challenge of collecting data over a sufficiently large volume of reciprocal space and the theoretical challenge of modeling the results. However, instrumental and computational advances at both x-ray and neutron sources now allow the efficient measurement and rapid transformation of reciprocal space data into three-dimensional pair distribution functions, providing model-independent images of nanoscale disorder in real space. By eliminating Bragg peaks before the transformation, 3D-∆PDF measurements image defect-defect correlations directly, displaying only the probabilities of interatomic vectors that deviate from the average structure. I will give examples of the use of this method to probe the structure and correlation length of order-disorder transitions in intercalation compounds, the length scale and dimensionality of nematic correlations in iron arsenides, and the defect correlations in a superionic thermoelectric.
This work was supported by the U.S. Department of Energy, Materials Science and Engineering Division.

Faculty Host: Martin Greven
4:40 pm:
CM Journal Club in Tate 201
Subject: No journal club this week

Thursday, October 18th 2018
Speaker: Evan Tyler, University of Minnesota
3:35 pm:
Biophysics Seminar in B50 Tate
Speaker: Terry Hwa, Department of Physics, University of California at San Diego Physics and Astronomy Colloquium
(Note: Terry Hwa will not give a Biophysics Seminar but just a colloquium)
3:35 pm:
Speaker: Terry Hwa, University of California, San Diego
Subject: Bacterial growth laws and the origin of dimensional reduction
Refreshments in atrium after the Colloquium.

A cell is the smallest unit of a freely living system. Our understanding of cells is measured by our ability to predict cellular behaviors in response to environmental changes and genetic manipulations. Traditionally, researchers strive to gain insights into cellular behaviors through characterizing the underlying molecular interactions. This ‘bottom-up’ approach however requires a macroscopic number of largely inaccessible parameters in order to be predictive. I will describe a complementary ‘top-down’ approach based on quantitative phenomenology. Extensive quantitative experiments establish that the model bacterium E. coli organizes many of its behavioral responses in very simple manners in accordance to the rate of cell growth. The existence of these simple empirical relations (growth laws) despite myriads of complex molecular interactions is a striking manifestations of a tremendous degree of dimensional reduction occurring in living cells. I will describe how the growth laws can be used to make accurate predictions of cell behaviors without fitting parameters. I will also discuss how the magical dimension reduction can be accomplished by cells through clever strategy of gene regulation.

Faculty Host: Elias Puchner

Friday, October 19th 2018
12:20 pm:
Speaker: Zach Anderson
Subject: Neutron scattering study of antiferromagnetic excitations in HgBa2CuO4+δ
Speaker: Emilian Dudas (Ecole Polytechnique)
Subject: Hidden symmetries and Goldstone bosons from higher dimensions?

Free massless scalars have a shift symmetry. This is usually broken by interactions, such that quantum corrections induce a quadratically divergent mass term. In the Standard Model this leads to the hierarchy problem, the question why the Higgs mass is so much smaller than the Planck mass. We present an example where a large scalar mass term is avoided by coupling the scalar to an infinite tower of massive states, obtained from a six-dimensional theory compactified on a torus with magnetic flux. We show that the shift symmetry of the scalar is preserved in the effective four-dimensional theory despite the presence of gauge and Yukawa interaction terms.

Speaker: Adam Frank, University of Rochester
Subject: Blowing Away Exoplanets: The Photo-evaporation of Planetary Atmospheres

Mass loss from exoplanets driven by stellar photo-ionizing fluxes may be a fundamental process setting the final state of planetary atmospheres and, therefore, habitability. In this talk I present new results from 3-D AMR multi-physics simulations exploring the processes and consequences of atmospheric photo-evporation including its observation signatures.

3:35 pm:
Speaker: Jaipreet Virdi, University of Delaware
Subject: Mechanical Quackery: Electrical Cures for Deafness in the United States, 1880-1930
Refreshments served at 3:15 p.m.

During the late nineteenth century, electrical entrepreneurs began to glut the direct-to-consumer medical market with a plethora of electrotherapy machines for curing deafness. They claimed their machines fostered a world of unbridled optimism for restoring bodies to health; in a few sessions, these machines could harness the power of electricity to jolt dead ears or apply a vibratory force to “break up” deposits in the ear. Although ear specialists—known as “aurists”—denounced such “cure all” treatments for deafness, electrical entrepreneurs made no demarcation between congenital and non-congenital cases of hearing loss, thus appealing to patient-consumers frustrated with traditional therapeutics. Electrotherapy devices also offered an effective but gentle remedy to those distrustful or skeptical of compressed powdered pills, nefarious nostrums, or other patented goods available for purchase. By the 1930s, a growing public awareness of medical fraud, combined with stricter federal regulation, led to the steady decline of electrotherapeutics usage in the home; while most mechanical deafness cures were dismissed by the American Medical Association and the Food & Drug Association as quackery in its finest forms, these devices highlight the fluid boundaries that existed between healthcare practices, and the many ways consumers attempted to regain control over their health. More broadly, these devices convey a broader historical context for understanding how and why deaf consumers attempted to cure or normalize their hearing loss.

4:40 pm:
Speaker: Ke Wang, Condensed Matter
Subject: Novel Quantum Physics in van der Waals Nanostructures

Monday, October 22nd 2018
12:15 pm:
Speaker: Wenlei Chen, UMN
Subject: Novel search for TeV-initiated pair cascades in the intergalactic medium

The observed magnetic fields in galaxies and galaxy clusters are believed to result from dynamo amplification of weak magnetic field seeds whose origin remains a long-standing open question. Beams of TeV gamma-rays from blazar jets can be used to infer the intensity, coherence length, and helicity of the intergalactic magnetic field. Intergalactic magnetic fields deflect the electron-positron pairs produced by TeV gamma-rays from blazars, resulting in broadened beams of secondary GeV gamma-rays known as pair halos. Such pair-cascades develop along the projected direction of the blazar jet, which is known from imaging radio observations. We searched for GeV pair halos in Fermi-LAT data around 12 high-synchrotron-peaked BL Lacs with well-determined jet orientation from VLBA radio observations. Our study exploits the expected asymmetry of blazar pair halos and uses advanced simulations of the pair cascades to improve the sensitivity of previous studies and increase the signal to noise. Although we find no significant detection, a 2-sigma hint for an extended pair halo along the direction of the jet appears in the stacked LAT data in the 30-300 GeV energy range, corresponding to an intergalactic magnetic field with strength of about 1E-15 Gauss. This magnetic field value is consistent with similar hints from independent studies using LAT data. We will present the results of our analysis and discuss the limitations of pair-halo searches due to astrophysical uncertainties. Finally, assuming that the apparent convergence on B ~ 1E-15 G is not coincidental, we will outline a clear path towards a positive detection of blazar pair halos with future space-borne and ground-based gamma-ray observatories.

Faculty Host: Patrick Kelly

Tuesday, October 23rd 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Ermal Rrapaj, University of Minnesota & University of California, Berkeley
Subject: Supernovae and neutron stars: Constraining dark matter through nuclear interactions
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Julie Vievering, P.S. Athiray and Sophie Musset
Subject: Investigating high-energy solar phenomena with the FOXSI-3 sounding rocket

Wednesday, October 24th 2018
1:25 pm:
Speaker: Johnpierre Paglione, University of Maryland, College Park
Subject:  High-spin superconductivity in topological half-Heusler semimetals

In all known fermionic superfluids, Cooper pairs are composed of spin-1/2 quasi-particles that pair to form either spin-singlet or spin-triplet bound states. The "spin" of a Bloch electron, however, is fixed by the symmetries of the crystal and the atomic orbitals from which it is derived, and in some cases can behave as if it were a spin-3/2 particle. The superconducting state of such a system allows pairing states to form beyond triplet, with higher spin quasi-particles combining to form quintet or even septet pairs. After reviewing experimental evidence for high-spin pairing in the exotic superconducting state of the half-Heusler compound YPtBi, I will introduce our recent work elucidating the influence of spin-orbit coupling on both the normal and superconducting states of this system

To be announced
4:40 pm:
CM Journal Club in Tate 201
Subject: Boltzmann Transport Equation

Thursday, October 25th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Oleg Krichevsky, Molecular Biophysics Lab, Ben-Gurion University
Subject:  T cell communication through cytokines follows a simple sink-diffusion model

Immune cells communicate by exchanging cytokines to achieve a context-appropriate response, but the distances over which such communication happens are not known. We used theoretical considerations and experimental models of immune responses in vitro and in vivo to quantify the spatial extent of cytokine communications in dense tissues. Using T cell exchange of IL-2 as a model system, we established that competition between cytokine diffusion and consumption generated spatial niches of high cytokine concentrations with sharp boundaries. The size of these self-assembled niches scaled with the density of cytokine-consuming cells, a parameter that gets tuned during immune responses. In vivo, we measured interactions on length scales of 80–120 um, which resulted in a high degree of cell-to-cell variance in cytokine exposure. Despite the complexity of the immune organs, the profiles of cytokine fields both in vitro and in vivo quantitatively follow the predictions of a simple model, essentially without any free parameters.

Ref. Oyler-Yaniv A, Oyler-Yaniv J, Whitlock B.M, Liu Z, Germain R.N, Huse M, Altan-Bonnet G. and O. Krichevsky (2017) , Immunity, 46, 609-620.

Faculty Host: Elias Puchner
Speaker: Nathan Eggen and Aliza Beverage, University of Minnesota
3:35 pm:
Speaker: Steven Gubser, Princeton
Subject: Number theory and spacetime
Refreshments in atrium after the Colloquium.

Our description of spacetime relies on the real numbers and hence is wedded to arbitrarily small intervals of length and time. But quantum theory hints at the existence of a smallest possible length, the Planck length. Number theory provides an alternative to the real numbers known as the p-adic numbers. Recent work has argued that quantum field theory defined over the p-adic numbers is holographically dual to a discrete spacetime. Constructions related to p-adic numbers also have a surprisingly prominent role in the early development of the renormalization group. I will explain what the p-adic numbers are and provide some intuition for what they are good for in string theory and beyond. The ultimate aim of using them to understand quantum gravity is ambitious indeed, but I will explain some first steps that give hope for the future.

Bio: Steve Gubser got his PhD from Princeton University in 1998, working with Igor Klebanov on what became the gauge-string duality. He did a post-doc at Harvard, then joined the faculty at Princeton. After a year at Caltech, he returned to Princeton and has been there ever since. He is now the Associate Chair for Undergraduates in Physics, and he is a recent recipient of a Simons Young Investigator award.

Faculty Host: Priscilla Cushman

Friday, October 26th 2018
12:20 pm:
Speaker: Yiming Wu
Subject: Special role of the first Matsubara frequency for superconductivity near a quantum-critical point --the non-linear gap equation below $T_c$ and spectral properties along the real frequency axis.
Speaker: Steven Gubser (Princeton)

p-adic AdS/CFT is a version of the gauge-gravity duality where the boundary theory is defined over the p-adic numbers and the bulk is a discrete graph. A variant of p-adic field theories has emerged from recently proposed cold atom experiments based on sparse couplings. I will explain how a simplified version of these theories interpolates between an ordinary continuum field theory and p-adic field theory as a spectral exponent is dialed.

Speaker: Bin Chen,Center for Solar Terrestrial Research, New Jersey Institute of Technology
Subject: Solar Flare Observations with the Karl G. Jansky Very Large Array

Known as one of the most capable radio telescopes for studying various astronomical objects in the universe, the Karl G. Jansky Very Large Array (JVLA) is also commissioned to observe the Sun in a wide range of radio wavelengths from <1 GHz to 18 GHz. Thanks to the Sun’s proximity, the JVLA can be configured as a powerful data machine when observing the Sun, capable of generating over one billion (1,000,000,000) radio images per hour of observing at an ultra-high time cadence (10 milliseconds), spectral resolution (~1%), and spatial resolution (~21”/f GHz). JVLA’s powerful dynamic spectroscopic imaging capability, combined with its high sensitivity, offer unique means for studying various radio emission from the Sun, particularly radio bursts emitted by energetic electrons accelerated in solar flares. We have recorded dozens of flare events with various sizes since 2011. The study of a subset of these flare events has yielded new insights on the magnetic energy release, particle acceleration and transport processes, which are not only important in solar flare physics, but also relevant in space physics and astrophysics contexts that involve magnetized plasma. I will discuss recent results based on these JVLA flare observations.

3:35 pm:
Speaker: Benjamin Goldberg , Department of Humanities and Cultural Studies, University of South Florida
Subject: Margaret Cavendish’s Medical Recipes: Medicine, Experience, and Natural Philosophy in Early Modern England
Refreshments served at 3:15 p.m.

In collaboration with Justin Begley (Helsinki), I am working on a transcript of Margaret Cavendish’s family book of medical recipes (often called ‘receipts’). This previously unpublished manuscript (MS Pw V 90, located at the University of Nottingham, UK) is a fascinating and rare document, written by a number of hands (including Margaret’s), and which provides some unique insights into Cavendish’s thought.

In this talk, I describe the contents of the MS, placing it in its proper context, namely, recent historiography on food, medicine, and cooking in early modern England. I focus, in particular, on how this work differs from most other recipe collections, both manuscript and printed, in, e.g., its exclusive medical focus and its inclusion of doctor’s reports. I then discuss how to interpret this work within the larger context of Cavendish’s natural philosophy, noting that we must be careful in how we interpret it, since it is not exclusively her writing, though there is evidence she was the one who compiled and organized it. With this proviso, I argue that this MS places some pressure on the received view of Cavendish’s conception of experience and experiment, seemingly undermining her anti-experimentalism and penchant for speculation. When this MS is read along with Cavendish’s extensive, if scattered and disorganized, discussions of medicine and food, however, we can resolve these apparent tensions by carefully attending to the various roles that empirical experience plays in Cavendish’s thought. Taken together with recent historiography on non-traditional aspects of the Scientific Revolution (women, kitchens, cooking, etc), this work can help us define some of the novel ways that experience was thought about in these various alternative contexts.

I conclude with some thoughts on our historical accounts of experience by scholars such as Steven Shapin and Peter Dear. I argue that these accounts, while not untrue, also do not exhaust the ways in which these ideas were understood in early modern England. Our accounts of experience and experiment are thus in need of revision and expansion so as to adequately account for the complex ways in which these ideas were used by various thinkers beyond the canonical philosophers and scientists of early modernity.

4:40 pm:
Speaker: Michael Zudov, Condensed Matter

Monday, October 29th 2018
12:15 pm:
Speaker: Clem Pryke, UMN
Subject: Latest constraints on primordial gravitational waves from BICEP/Keck

The BICEP/Keck experiments at South Pole in Antarctica measure the
polarization of the Cosmic Microwave Background (CMB) at degree angular
scales. The B-mode of the polarization pattern may reveal evidence for
primordial gravitational waves spawned by the hyper inflation of the early
universe. I will describe the instrument, observations and analysis, including
the new BK15 results which have recently been released. I will also describe
the future plans for BICEP Array - parts of which are now taking shape in PAN.

Faculty Host: Vuk Mandic

Tuesday, October 30th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
To be announced
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: John Wygant, University of Minnesota
Subject: The role of Poynting flux in powering ion and electron energy flux of the cusp wind

In this talk, we present measurements of steady state and wave Poynting flux, as well as ion and electron energy flux flowing parallel to the magnetic field in the cusp region of the Earth's magnetosphere in order to assess the in flow and out flow of energy along these magnetic flux tubes. These measurements are obtained by the Polar spacecraft at 3-5 Re geocentric distances and by the FAST spacecraft at 1.6 Re and below. We find that during "active times" at Polar altitudes, there is a very substantial and steady net flow of ion energy flux away from the Earth which ranges between 10 and >100 mW/ m2 (normalized to flux tube area at 100 km). Average values of the net ion energy flux at 3-5 Re during less active periods are on the order of 1 mW/m2. The energy flux of ions and electrons at the lower altitudes observed by FAST are generally downward. The observations of large net energy flux out of the ionosphere indicate that the process of ion energization and outflow in the cusp is one of the most energy intensive processes in the Earth's magnetosphere rivaling the energy invested in the collisionless acceleration of electron beams associated with auroral arcs. During extreme events, it involves the formation of a low beta (0.1) subsonic wind of plasma flowing away from the Earth on cusp field lines at velocities of 50 km/s to several hundred km/s. A related question is what powers this system. The Polar spacecraft measurements provides evidence for large values of "steady state" and "wave" Poynting flux flowing earthward along magnetic field lines over a band-pass from 0.1 mHz to 1 Hz (spacecraft frame) and there is strong evidence that this is the only mode of energy transfer parallel to the magnetic field capable of powering this energetic wind. A comparison of incident Poynting flux to outflowing ion energy flux shows that the energy coupling/acceleration mechanism is likely to be quite efficient. In addition, measurements show the Poynting flux is concentrated in the large-scales, not in the smaller scale waves. These observations motivate interest in a number of unresolved issues related to if and how the large scale Poynting flux is transferred to small scales waves that can efficiently heat the plasma. This energy flow and its partitioning is an interesting contrast to that observed in conjunction with auroral electron acceleration on the nightside. This wind is also analogous in some important ways to the solar wind, which is also believed to be driven by Poynting flux. In principle, similar winds could also exist at other planetary magnetospheres.

Wednesday, October 31st 2018
1:25 pm:
Speaker: Adam Wei Tsen, University of Waterloo, Institute for Quantum Computing
Subject:  New Phase Transitions in Atomically Thin Quantum Materials

We have recently demonstrated an experimental platform to isolate 2D quantum materials that are unstable in the ambient environment. I will discuss our studies of the Weyl semimetal candidate, 1T’-MoTe2, and layered magnetic insulator, CrI3, in the atomically thin limit, made possible using this technique. In MoTe2, lowering dimensionality suppresses the inversion symmetric monoclinic phase, driving the Weyl ground state up to and beyond room temperature. The different electronic structure of thin samples is studied by magnetotransport measurements at low temperature. In CrI3, we observe a very large negative magnetoresistance effect that is quantitatively comparable to colossal magnetoresistance in the manganites. I will explain the origin of this effect and discuss some new opportunities for other 2D magnets.

Faculty Host: Ke Wang
To be announced
4:40 pm:
CM Journal Club in Tate 201
Subject: No journal club this week

Thursday, November 1st 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Douglas G. Mashek, Professor, Department of Biochemistry, Molecular Biology and Biophysics and Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, University of Minnesota
Subject: The fascinating world of lipid droplet biology

Lipid droplets are recognized to be the primary storage form of energy in most cell types. While this important function is critical to supply cells or organisms with energy during times of nutrient deprivation, their role beyond energy storage has largely been unexplored. Our laboratory has focused on elucidating the mechanisms through which lipid droplets communicate within cells to coordinate energy storage with cell signaling and metabolism. Our work on hepatic lipid droplets has identified important functions for these dynamic organelles in regulating lipid and glucose metabolism, hormone signaling and cell proliferation. Specifically, data will be presented showing that lipid droplet catabolism promotes signaling networks to control mitochondrial biogenesis and function. Moreover, recent insights into the mechanisms through which lipid droplets are catabolized via autophagic pathways will also be discussed. In summary, this presentation will highlight novel roles for lipid droplets and their metabolism in cellular and organismal biology and their importance in human health.

Speaker: Chris Nolting, University of Minnesota
3:35 pm:
Speaker: Robert Kleinberg, Columbia University & Boston University
Subject: mK to km: How Millikelvin Physics is Reused to Explore the Earth Kilometers Below the Surface
Refreshments in atrium after the Colloquium.

Investigations of the superfluid phases of liquid helium-3 would seem to have little application to the study of rock formations thousands of meters below the surface of the earth. However, the physicist’s tool box is versatile, and techniques used in one field of study can be reused, with appropriate adaptation, in very different circumstances.

The temperature of liquid helium-3 in the millikelvin range can be measured using an unbalanced-secondary mutual inductance coil set designed to monitor the magnetic susceptibility of a paramagnetic salt. The loss signal is discarded by phase sensitive detection. Now consider the task of measuring the electrical conductivity, at centimeter scale, of the earth surrounding a borehole. Turn the mutual inductance coil set inside out, with secondary coils arranged to be unbalanced with respect to the rock wall. Instead of discarding the loss signal, use it to measure conductivity. A sensor based on this principle has been implemented in a widely deployed borehole geophysical instrument, used to estimate the prevailing direction of the wind millions of years ago, or to decide where to drill the next well in an oilfield.

Nuclear magnetic resonance may seem a very improbable measurement of the rock surrounding a borehole. Conventionally, we place the sample (which might be a human being) inside the NMR apparatus. In borehole deployment, the instrument is placed inside sample, the temperature is as high as 175C, pressure ranges to 140 MPa, and measurements must be made while moving at 10 cm/s. Apparatus with these specifications have been deployed worldwide, and are used to measure a number of rock properties, including the distribution of the sizes of pores in sedimentary rock, and the viscosity of oil found therein. They have also been used for geological and oceanographic studies in northern Alaska, and at the seafloor offshore Monterey, California.

Faculty Host: Shaul Hanany

Friday, November 2nd 2018
12:20 pm:
Speaker: Xuzhe Ying
Subject: Anomalous Hall Effect in Symmetry Protected Topological Metals
Speaker: Anson Hook (U. Maryland)
Subject: New approaches to the Hierarchy problem

We present two new approaches to the Hierarchy problem. The first utilizes non-linearly realized discrete symmetries. The cancelations occur due to a discrete symmetry that is realized as a shift symmetry on the scalar and as an exchange symmetry on the particles with which the scalar interacts. The second approach allows for a large Higgs mass, but the Higgs mass expanded around the minimum of the potential is small. This approach is analogous to models of the dilaton where the quartic is large at tree level, but small when expanded around the minimum of the potential.

Speaker: Vanessa Bailey, NASA Jet Propulsion Laboratory (JPL)
The WFIRST Coronagraph Instrument

The Coronagraph Instrument (CGI) for NASA's Wide Field Infrared Survey Telescope (WFIRST) will constitute a dramatic step forward for high-contrast imaging, integral field spectroscopy, and polarimetry of exoplanets and circumstellar disks, aiming to improve upon the sensitivity of current direct imaging facilities by 2-3 orders of magnitude. Furthermore, CGI will serve as a pathfinder for future exo-Earth imaging and characterization missions by demonstrating wavefront control, coronagraphy, and spectral retrieval in a new contrast regime. I will discuss the status of the instrument design, some of its key new technologies, and its potential science yield.

3:35 pm:
There will be no colloquium this week.
4:40 pm:
Speaker: Robert Lysak, MIFA

Monday, November 5th 2018
12:15 pm:
Speaker: Guillermo Fernandez Moroni, Fermilab
Subject: Dark Matter and Neutrino direct detection using CCDs

The talk presents the status and prospects of direct detection of dark matter and neutrinos on experiments based on silicon CCDs (Charge Coupled Devices). It reviews the concept and results of the CONNIE (Coherent Neutrino Nucleus Interaction Experiment) experiment currently running near by a 4 GW power nuclear reactor in Brazil; and DAMIC (Dark Matter in CCD) experiment operative at SNOLAB. These are twin experiments at different locations with an effective energy threshold of ~50 eVee. Also, a new CCD technology with much lower energy threshold (~3 eVee) is presented. This “new” CCD is called Skipper CCD and is going to be used on a new experiment for direct detection of light dark matter called SENSEI (Sub-Electron Noise Skipper Experimental Instrument) that uses a non-destructive readout technique to achieve stable single electron discrimination in the silicon. This is the first instrument to achieve single electron counting for the whole dynamic range with stable operation over millions of pixels on a large-area detector. This low threshold allows for unprecedented sensitivity to the largely unexplored, but theoretically well-motivated, area of sub-GeV dark matter models. We’ll discuss the reach and prospects of the SENSEI experiment currently under construction, which will use 100 grams of Skipper CCDs. We will also present the lessons learned from a small scale prototype currently operating in the MINOS cavern at Fermilab.

Faculty Host: Vuk Mandic

Tuesday, November 6th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Sheng Tian, University of Minnesota
Subject: Comparisons of auroral structures and in-situ observations
3:00 pm:
Thesis Defense in PAN 110
Speaker: Justin Watts, University of Minnesota
Subject: Spin Relaxation and Size Effects in Cu and Al Nanowires
This is the public portion of Mr. Watts' Thesis Defense. His advisors are Paul Crowell and Chris Leighton.

Wednesday, November 7th 2018
1:25 pm:
Speaker: Jason Petta, Princeton University
Subject: Microwave Spectroscopy of Valley States in Silicon

The bulk conduction band of Si has six equivalent valleys. Strain in Si/SiGe heterostructures partially lifts the six-fold valley degeneracy by raising the energy of the four in-plane valleys. It is known that large electric fields can lift the degeneracy of the remaining two low-lying valleys. However, the measured valley splittings range from 10 – 300 μeV, suggesting that microscopic details such as interface roughness and disorder impact the valley splitting. In this lecture I will describe how microwave spectroscopy can be applied to probe valley states in silicon nanostructures [1]. In the first experiment, a cavity coupled Si double quantum dot is probed using microwave frequency photons. The transmission of the photons through the microwave cavity displays signatures that are consistent with the valley degree of freedom and the data can be modeled using cavity input-output theory [2]. We also use Landau-Zener interferometry to probe the low-lying energy level structure of a silicon double quantum dot. The observed Landau-Zener interference pattern persists down to low driving frequencies of 50 MHz, suggesting relatively long-lived charge coherence. Low-lying valley states result in a unique Landau-Zener interference pattern that is in contrast with measurements on conventional two-level charge qubits [3]. These new probes of valley states have high energy resolution and may be applied to other low energy degrees of freedom.

1. Burkard and Petta, PRB 94, 195305 (2016).
2. Mi, Peterfalvi, Burkard, and Petta, PRL 119, 176803 (2017).
3. Mi, Kohler, and Petta, PRB 98, 161404(R) (2018).

Faculty Host: Ke Wang
Speaker: Nick West, Fermilab
Subject: Searches for new physics with Z boson leptonic decays and large missing transverse momentum
4:40 pm:
CM Journal Club in Tate 201
Subject: Z2 Topological Index

Thursday, November 8th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Isaac Angert, graduate student in Jochen Mueller’s lab, School of Physics and Astronomy, University of Minnesota
Subject: Ultra-sensitive detection of plasma membrane binding and nanometer lengths with dual-color fluorescence z-scan in live cells

Delicate and transitory protein engagement at the plasma membrane (PM) is crucial to many cellular functions and disease states, including cell motility, signal transduction, and the budding and entry steps in the life cycle of many viruses. We describe quantification of PM binding by the use of two-photon dual color z-scan (DC z-scan) deconvolution in cells co-expressing a fluorescently labeled protein of interest along with a soluble fluorescent protein with a distinct color that serves as a reference to delineate the cytoplasmic extent. We show that this technique can detect very small amounts of PM binding that are otherwise extremely difficult to discern. Due to the nature of the two-photon excitation, the DC z-scan PM binding assay technique attains very low levels of systematic artifacts, for which we provide observational upper bounds. We further extend the technique to interrogate length displacements between dual-color fluorescently labeled protein species and show that the DC z-scan technique resolves nanometer scales. We utilize DC z-scans to investigate the passage of retroviral assembly proteins through the actin cortex in live cells, and suggest that the dense cortical meshwork may present a barrier to the assembly and budding of retroviruses such as human immunodeficiency virus.

3:35 pm:
Speaker: Jason Petta, Princeton University
Subject: Quantum Computing with Electron Spins in Silicon
Refreshments in atrium after the Colloquium.

Electron spins are excellent candidates for solid state quantum computing due to their exceptionally long quantum coherence times, which is a result of weak coupling to environmental degrees of freedom. However, this isolation comes with a cost, as it is difficult to coherently couple two spins in the solid state, especially when they are separated by a large distance. Here we combine a large electric-dipole interaction with spin-orbit coupling to achieve spin-photon coupling [1]. Vacuum Rabi splitting is observed in the cavity transmission as the Zeeman splitting of a single spin is tuned into resonance with the cavity photon. We achieve a spin-photon coupling rate as large as gs/2 = 10 MHz, which exceeds both the cavity decay rate /2 = 1.8 MHz and spin dephasing rate /2= 2.4 MHz, firmly anchoring our system in the strong-coupling regime [2]. Moreover, the spin-photon coupling mechanism can be turned off by localizing the spin in one side of the double quantum dot. These developments in quantum dot cQED, combined with recent demonstrations of high-fidelity two-qubit gates in Si, firmly anchor Si as a leading material system in the worldwide race to develop a scalable quantum computer [3].

1. Mi et al., Science 355, 156 (2017).
2. Mi et al., Nature 555, 599 (2018).
3. Zajac et al., Science 359, 439 (2018).

Friday, November 9th 2018
12:20 pm:
Speaker: Yilikal Ayino, University of Minnesota
Subject: Multi-band two-dimensional superconductivity above the Pauli limit in NdxSr1-xTiO3
Speaker: Keisuke Harigaya (IAS, Princeton)
Subject: Higgs parity, strong CP problem and unification

The quartic coupling of the Standard Model Higgs nearly vanishes at a high energy scale. We show that this is explained by the parity symmetry and its spontaneous break down by the condensation of the parity partner of the Higgs. The parity can solve the strong CP problem. The theory is embedded into SO(10) unification and the precise gauge coupling unification is achieved.

Speaker: Gautham Narayan, Space Telescope Science Institute
Subject: From Tens to Tens of Thousands: Supernovae Science in the Big-Data Era

’ll discuss SN2018oh and SN2018agk -- two of the spectroscopically confirmed SNIa with exceptional early-time observations discovered by the Kepler Extragalactic Survey (KEGS) with K2 during the forward-facing campaign 17. I’ll detail the constraints we infer from comparing the data of these two objects to physical models of type Ia explosions, and discuss the implications for different SNIa progenitor scenarios. But two does not a sample make, and Kepler SN are relatively rare events. To find more of them, we must move to wide-field ground-based surveys. I’ll discuss work to use cutting edge data science and machine learning techniques to identify such events within the tens of thousands being discovered in real-time. Finally, I’ll outline how we’re preparing the community to jump scale from the current-generation of surveys to LSST.

3:35 pm:
Speaker: Andrew J. Hogan, Department of History, Creighton University
Subject: Reform or Exclude?: Debating Medicine’s Role in Disability and Mental Health
Refreshments served at 3:15 p.m.
4:40 pm:
Speaker: Randall Victora, ECE

Monday, November 12th 2018
12:15 pm:
Subject: There will be no seminar this week.
Faculty Host: Vuk Mandic

Tuesday, November 13th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
1:15 pm:
Space Physics Seminar in Tate 301-20
Speaker: Bob Lysak, University of Minnesota
Subject: Kinetic Alfven Waves and Juno Observations of Auroral Particle Acceleration at Jupiter
Please note: early start time for the seminr, this week only.

Wednesday, November 14th 2018
1:25 pm:
Speaker: Mathias Scheurer, Harvard University
Subject: Gauge theories of fluctuating antiferromagnetism for the cuprate superconductors

One of the most mysterious phases of the cuprate high-temperature superconductors is the “pseudogap” state: despite its Fermi-liquid-like electrical transport properties, the size of the Fermi surface is smaller than that predicted by the Luttinger theorem of Fermi liquid theory. In this talk, I will discuss gauge theories of doped fluctuating antiferromagnets that we propose as effective field theories for the pseudogap phase. By virtue of exhibiting “topological order”, these theories allow to circumvent Luttinger’s theorem while exhibiting the charge transport of a Fermi liquid. The presentation will focus on a direct comparison of predictions of these gauge theories with both numerical studies of the strongly coupled Hubbard model and high-resolution photoemission data. The good agreement can be seen as at least indirect evidence for topological order in the phase diagram of the cuprate superconductors. We will also discuss the additional symmetry breaking, such as the formation of charge-density-wave, nematic, or loop-current order, that can occur at low temperature and comment on the quantum critical point in our theory.

Faculty Host: Rafael Fernandes
To be announced

Thursday, November 15th 2018
08:00 am:
Speaker: Lee Penn, CHEM and Diversity Committee
10:10 am:
Biophysics Seminar in PAN 120
Speaker: John Marko, Northwestern University
Subject: Single-molecule studies of protein-DNA interactions

All processing of DNA - transcription, replication, recombination and
repair - depend on the interactions of proteins with DNA. I will discuss
single-molecule methods for analyzing protein-DNA interactions, starting
with the (statistical)-mechanical response of DNA molecules and how
monitoring that can allow novel quantitative studies of proteins that fold
and change topology of DNA molecules. I will then describe a phenomenon
that appears pervasive for biomolecule interactions - "facilitated
dissociation" - that makes rates of turnover of molecular complexes in vivo
very different from what we observe in vitro.

Speaker: Jett Priewe, University of Minnesota
3:35 pm:
Speaker: John Marko, Northwestern University
Subject: Physics of chromosome folding and disentanglement
Refreshments in atrium after the Colloquium.

All biological phenomena depend on genetic information which is encoded
into the base-pair sequence along the very long DNA molecules found in all
living cells. The DNAs in chromosomes, in addition to being biologically
important, are amazing physical objects, being 2 nanometers wide and (in
humans) several centimeters in length. I will explain how the cell takes
care of these long, fragile chromosomal DNAs and how it uses DNA itself as
a key mechanical component of the cell nucleus. Then, during and
following DNA replication, our cells face the gigantic challenge of
figuring out how to topologically separate those long polymers from one
another. I will discuss our current understanding of the "lengthwise
compaction" mechanisms underlying this process, focusing on the interplay
between "loop-extruding" SMC complexes (mainly condensin) and
DNA-topology-changing topoisomerase II.

Faculty Host: Elias Puchner

Friday, November 16th 2018
12:20 pm:
Speaker: Sajna Hameed
Subject: Neutron and X-ray scattering study of the ferro-antiferromagnetic cross-over in Y1-xLaxTiO3
Speaker: Alba Grassi (SCGP Stony Brook)
Subject: A solvable deformation of Quantum Mechanics
Speaker: Brian O'Shea, Michigan State University
Subject: Connecting the first stars in the universe to the Milky Way

Galaxies are complicated beasts - many physical processes operate simultaneously, and over a huge range of scales in space and time. As a result, creating accurate models of the formation and evolution of galaxies over the lifetime of the universe presents tremendous challenges. In this talk I will discuss these challenges and their solutions, and will explain how large-scale computational models can be used to gain insights into the very first galaxies that formed in the universe (over 13 billion years ago!), and how we can use both these computational models and observations of the Milky Way and its neighbors to infer how galaxies have grown and evolved in the intervening time.

3:35 pm:
Speaker: Daniel Rood, Department of History, University of Georgia
Subject: El Principio Sacarino: Organic Chemistry Meets Racial Capitalism in the Cuban Sugar-Mill
Refreshments served at 3:15 p.m.
4:40 pm:
Speaker: Jeremiah Mans, High Energy

Monday, November 19th 2018
12:15 pm:
Speaker: Soumyajit Mandal, Case Western Reserve University
Subject: Ultra-steep-spectrum Sources in Galaxy Clusters

Faculty Host: Thomas W. Jones

Tuesday, November 20th 2018
11:15 am:
Nuclear Physics Seminar in Physics 301-20 Tate
Speaker: Mauricio Martinez Guerrero, North Caroline State University
Subject: Hydrodynamic Fluctuations and Lower Bounds of the Transport Coefficients

In this talk I will discuss the effects of hydrodynamic
fluctuations in non-relativistic and relativistic setups. Within the
framework of stochastic hydrodynamics I obtain a number of model
independent results, including the long-time tail of different
transport coefficients, and the leading non-analyticity of the
correlators of energy, momentum and particle density in
non-relativistic and relativistic setups. The presence of hydrodynamic
fluctuations induce lower bounds on the transport coefficients by
analyzing the low frequency limit of different correlation functions.
I determine the lower bounds of the bulk viscosity over entropy ratio
in a cold Fermi gas near unitarity. When extending this analysis to
the case of a U(1) conformal relativistic expanding fluid we observe
that the values of the shear viscosity and heat conductivity are
bounded from below. In both setups, non-relativistic and relativistic
one, the lower bounds on the transport coefficients are weakly
dependent on assumptions regarding the range of applicability of fluid
dynamics.

1:25 pm:
Space Physics Seminar in Tate 301-20
Speaker: Aaron Breneman, University of Minnesota
Subject: Followup to Global-scale coherence modulation of radiation-belt electron loss from plasmaspheric hiss.
4:00 pm:
Speaker: Xiaoyu Wang, University of Chicago
Subject: Electrical transport near an Ising-nematic quantum critical point
Note change of time and day, this week only.

An electronic nematic order spontaneously breaks the rotation symmetry of the many body system, making various physical properties anisotropic. It has been observed in various systems, in particular the cuprate and iron-based high temperature superconductors. In the vicinity of a nematic quantum critical point — achieved by tuning some external parameter such as pressure or doping — the physics is described by that of low-frequency long-wavelength order parameter fluctuations coupled to a Fermi surface. However, due to the momentum-conserving nature of the induced electron-electron interaction, the temperature dependence of the resistivity near an Ising nematic QCP remains unclear. In this talk, we shed light on the problem by incorporating disorder and Umklapp process into the low-energy theory. Our work can be viewed as solving an extended Boltzmann equation, with a collision integral that accounts for complicated multi-particle scattering processes important near the QCP

Faculty Host: Rafael Fernandes

Wednesday, November 21st 2018
To be announced.

Thursday, November 22nd 2018
No journal club, Thanksgiving Holiday

Friday, November 23rd 2018
Subject: NO SEMINAR - THANKSGIVING
4:40 pm:
Thanksgiving - there will not be a speaker this week.

Monday, November 26th 2018
12:15 pm:
Speaker: Sharan Banagiri, UMN
Subject: Gravitational wave searches for the post-merger remnants of GW170817

In August 2017, the LIGO and Virgo detectors detected gravitational waves from a binary neutron star merger, GW170817. The merger and its aftermath was also seen across the electromagnetic spectrum, with the combined observations providing a wealth of new data and opening the door to new cosmological and astrophysical measurements. However, one of the things we do not know yet is the fate of the merger remnant. Gravitational waves could be one way to detect the nature of a binary neutron star merger remnant, and a detection can be used to bound the upper mass limits of neutron stars and probe the equation of state at those high masses. In this talk I will describe the searches done by LIGO and Virgo collaborations to try and detect such a remnant from GW170817. I will also discuss ongoing development of parameter estimation methods of signals from long lived merger remnants and what we can look forward to in future observing runs.

Faculty Host: Vuk Mandic

Tuesday, November 27th 2018
11:15 am:
Nulear Physics Seminar in Physics 301-20 Tate
Speaker: Fabian Rennecke, Brookhaven National Laboratory
Subject: Strangeness Neutrality and the Phase Structure of QCD

Since the incident nuclei in heavy-ion collisions do not
carry strangeness, the global net strangeness of the detected hadrons
has to vanish. We show that there is an intimate relation between
strangeness neutrality and baryon-strangeness correlations. In the
context of heavy-ion collisions, the former is a consequence of quark
number conservation of the strong interactions while the latter are
sensitive probes of the character of QCD matter. We investigate the
sensitivity of baryon-strangeness correlations on the freeze-out
conditions of heavy-ion collisions by studying their dependence on
temperature, baryon- and strangeness chemical potential. The impact of
strangeness neutrality on the QCD equation of state at finite chemical
potentials will also be discussed. We model the low-energy sector of
QCD by an effective Polyakov loop enhanced quark-meson model with 2+1
dynamical quark flavors and use the functional renormalization group
to account for the non-perturbative quantum fluctuations of hadrons.

12:15 pm:
Speaker: Evan Tyler, University of Minnesota
Subject: A Statistical Study of High Amplitude Whistler-mode Waves Using 5 Years of Van Allen Probes Data
Note change of time and location, this week only. This is the public portion of Mr. Tyler's Thesis Defense.

Abstract: We present the first statistical analysis with continuous data coverage and non-averaged amplitudes of the prevalence and distribution of high-amplitude (> 5 mV/m or > 50 pT) whistler- mode waves in the outer radiation belt using 5 years of Van Allen Probes data. Large-amplitude electric fields are most common above L=3.5 and between MLT of 0-7 where they are present 1-4% of the time. Large-amplitude magnetic fields are most common above L=4.5 and between MLT of 0-14 where they are present 1-6% of the time. During high geomagnetic activity, high-amplitude whistler-mode wave occurrence rises above 30% in some regions. During these active times the plasmasphere erodes to lower L and a significant population of large-amplitude, quasi-electrostatic whistler waves are observed at the plasmapause boundary at low L (3.5-4) in the pre-dawn sector. Because our knowledge of the distribution of magnetospheric chorus and other whistler mode waves in the magnetosphere has been primarily built on studies using time averaged data, the space physics community has previously been unable to determine the generation, prevalence, or impact of large-amplitude whistler-mode waves in the magnetosphere. Since these waves were first observed, their behavior and importance has been poorly constrained. These new results have important implications for modeling radiation belt particle interactions with chorus, as large-amplitude waves interact non-linearly with electrons. This also may provide clues regarding the mechanisms which result in growth to large amplitudes.

12:15 pm:
Thesis Defense in PAN 110
Speaker: Evan Tyler
Subject: High Amplitude Whistler-Mode Waves

Wednesday, November 28th 2018
1:25 pm:
Speaker: Kimberley Hill, CEGE
Subject: Phase transitions in the rheology of granular mud
Faculty Host: James Kakalios

Thursday, November 29th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Santosh Adhikari, graduate student in Elias Puchner's lab, School of Physics and Astronomy, University of Minnesota
Subject: Quantitative Super-resolution imaging and tracking of endosomes, lipid droplets and fatty acids in living cells

Single-Molecule localization microscopy (SMLM) is a rapidly evolving technique to study (sub-) cellular structures with ~20nm resolution. In SMLM techniques such as Photo-Activated Localization Microscopy (PALM), the high-resolution image of a structure is built by super-imposing localizations of single fluorophores from thousands of data acquisition frames. Hence, a limitation of SMLM has been the need to chemically fix cells in order to avoid blurring caused by motion. In this talk, I will present a motion correction PALM technique (mcPALM) that combines super-resolution with conventional imaging to track and correct for the motion of organelles in living cells while acquiring single molecule localizations. This technique allows us to obtain super-resolution images of moving organelles as well as to quantify their previously inaccessible dynamics. We validate this technique by resolving the size of individual endocytic vesicles and endosomes in live yeast cells and by quantifying the number of accessible PI3P binding sites they contain. The analysis of numerous cells revealed a characteristic vesicle maturation trajectory of composition and size as well as mechanistic information indicating that PI3P production precedes fusion into larger endosomes. These results are consistent with our previous study in fixed cells but yield additional insights in the dynamics of endosome maturation, transport and fusion.

I will also discuss our recent finding on the super-resolution capability of conventional BODIPY conjugates and their application to study the spatial distribution and mobility of fatty acids and lipid droplets under different metabolic states in live yeast cells with ~30 nm resolution.

Speaker: Huaqing Mao, University of Minnesota
3:35 pm:
Speaker: Marco Velli, UCLA
Subject: Parker Solar Probe: Understanding Coronal heating and Solar Wind acceleration
Refreshments in atrium after the Colloquium.

The magnetic field is fundamental to solar activity and shapes the inter-planetary environment, as shown by the full three dimensional monitoring of the heliosphere provided by measurements from many past and present interplanetary and remote sensing spacecraft. Magnetic fields are also the source for coronal heating and the very existence of the solar wind; produced by the sun’s dynamo and emerging into the corona, magnetic fields become a conduit for waves, act to store energy, and then propel plasma into the Heliosphere in the form of Coronal Mass Ejections (CMEs). Magnetic fields are also at the heart of the generation and acceleration of Solar Energetic Particle (SEPs) that modify the space weather environment of the Earth and other planets.

Parker Solar Probe (PSP) was launched in August 2018 to carry out the first in situ exploration of the outer solar corona and inner Heliosphere. Direct measurements of the plasma in the closest atmosphere of our star should lead to a new understanding of the questions of coronal heating, solar wind acceleration, and the generation, acceleration and propagation of SEPs.

In this lecture I will start from an introduction to our present knowledge of the magnetized solar corona and wind before describing the PSP scientific objectives, orbit, and instrument suites, and perhapse showing a glimpse from initial data. Emphasis will be on how PSP will confirm or falsify present models as well as the potential new discoveries stemming from the first exploration of the space inside the orbit of Mercury. I will also discuss how synergies with Solar Orbiter might lead us to accurately understand the state of the solar wind all the way from the corona into interplanetary space, a stepping stone
for understanding the dynamics of active magnetized plasmas throughout the universe.

Faculty Host: Robert Lysak

Friday, November 30th 2018
Speaker: No Colloquium
12:20 pm:
Speaker: Ezra Day-Roberts
Subject: Contrasting Ferromagnetism in FeS2 Pyrites Induced by Cobalt Doping and by Electrostatic Gating
Speaker: Jaroslav Trnka (UC Davis)
Subject: Effective field theories from soft limits of scattering amplitudes.

In the standard formulation soft limits of scattering amplitudes follow from the symmetries of the QFT. In this talk I will use the opposite approach, and show how a particular set of scalar and vector effective field theories can be fully specified using the constraints on scattering amplitudes. As a result, we rediscover some known effective field theories but also derive new ones.

Speaker: No Colloquium
4:40 pm:
Speaker:  Cynthia Cattell, MIFA

Monday, December 3rd 2018
12:15 pm:
Speaker: Karl Young, UMN
Subject:  Science Targets and Forecasts for PICO - Probe of Inflation and Cosmic Origins

The Probe of Inflation and Cosmic Origins (PICO) is a next generation space based mm/sub-mm imagining polarimeter with unprecedented sensitivity. With 21 frequency bands from 21-800 GHz, 1 arcmin resolution at 800 GHz, and combined map noise equivalent to 3250 Planck missions, PICO promises new discoveries across a wide range of science targets in physics, astrophysics, and cosmology. I will give an overview of the various science goals and predictions. These include detecting the signatures of inflation, measuring of the sum of neutrino masses, probing the reionization history of the universe, tracing the growth of structure, mapping Galactic magnetic fields, and many more! I will end with a brief explanation of how PICO achieves the sensitivity necessary for these science goals and discuss one important technology, low thermal conductance bolometers, which we have worked to develop for balloon-borne CMB telescopes.

Faculty Host: Shaul Hanany
12:30 pm:
FTPI Seminar in Tate 301-20
Speaker: Alexander Turbiner
Subject: Choreography in (non)-Newtonian gravity

By definition the choreography (dancing curve) is the trajectory
on which n classical bodies move chasing each other without collisions.
The first choreography (the remarkable Figure Eight) at zero angular
momentum was discovered unexpectedly by C Moore (Santa Fe) at 1993
for 3 equal mass bodies in R^3 Newtonian gravity numerically.
At the moment about 6,000 choreographies are known, all numerically
in Newtonian gravity. A number of 3-body choreographies is known
for Lenard-Jones potential again numerically.

Do exist (non)-Newtonian gravity for which dancing curve is known
analytically? - Yes, one example is known - it is algebraic lemniscate by
Jacob Bernoulli (1694) - and it will be the subject of the talk.
Astonishingly, Newtonian Figure Eight coincides with algebraic lemniscate
with accuracy 10 - 7- .

Faculty Host: Mikhail Shifman

Tuesday, December 4th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Jackson Olsen, University of Minnesota
Subject: Detecting Neutrinos from Supernovae

During a supernova vast numbers of neutrinos are released.
The energy of this neutrino emission dwarfs that of the light from the
explosion, yet the neutrinos are much more difficult to detect. I will
provide an overview of supernova neutrino detection techniques, and
discuss some of the information that might be learned from such a
detection.

Wednesday, December 5th 2018
1:25 pm:
Speaker: Damjan Pelc
Subject: Inhomogeneity in complex oxide superconductors

Some of the most studied unconventional superconductors, including the cuprate high-Tc materials, are oxides. In this talk, I will present some fresh insights into the physics of oxide superconductors, obtained with the help of two somewhat unusual experimental techniques - nonlinear magnetic response and uniaxial pressure. In particular, I will show that several very different complex oxides have the same superconducting precursor regime above the macroscopic transition temperature, Tc. This universal feature turns out to be related to subtle structural inhomogeneity shared by the different materials. Furthermore, we find that it is possible to manipulate this inhomogeneity by plastic deformation of the samples, in experiments that open up a new avenue in the study of unconventional superconductors. Finally, I will present some preliminary results on the intriguing effects of deformation and annealing on Tc in cuprates and strontium titanate.

Faculty Host: Martin Greven
Speaker: Kenneth Long, the University of Wisconsin
Subject: Cross section measurements and new physics searches with WZ vector boson scattering events at CMS

As the standard model (SM) Higgs boson looks increasingly like its SM expectation, expanded tests of the electroweak (EW) sector of the SM are a focal point of the long-term LHC program. Production of massive vector bosons via vector boson scattering provides a direct probe of the self-interactions of the massive vector bosons, which are intimately connected to the Higgs-Englert-Brout mechanism of EW symmetry breaking. A search for vector boson scattering of W and Z bosons has recently been performed by the CMS experiment using data collected in 2016. I will present this search as well as WZ cross section measurements, which are less dependent on theoretical inputs. This process is also sensitive to new physics in the EW sector. I will present interpretations of these results in terms of explicit models predicting additional charged Higgs bosons and in the generalized framework of dimension-8 effective field theory.

4:40 pm:
CM Journal Club in Tate 201
Speaker: Vipul Chaturvedi
Subject: In-operando probes in the ion gel gating of La0.5Sr0.5CoO3 epitaxial films

There will be a meeting on Dec. 5th.

Thursday, December 6th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Steven Vogel, NIH/NIAAA
Subject: VenusA206 dimers behave coherently at room temperature

Quantum biology posits that non-trivial coherent macromolecular interactions influence biological behavior. Identifying systems amenable to investigating how nature maintains coherence in a hot wet environment is desirable. We observe that homodimers of the yellow fluorescent protein VenusA206 behave coherently at room temperature using time-resolved fluorescence anisotropy measurements that reveal ultrafast energy transfer, circular dichroism spectra that exhibit Davydov-splitting, and a novel approach combining photon-antibunching and fluorescence correlation spectroscopy to compare the number of independent emitters and fluorescent molecules in the same sample. Our results support the hypothesis that fluorescent proteins have evolved a mechanism to allow coherent behavior under physiological conditions and have potentially far-reaching implications and applications, including the interpretation of fluorescent protein ‘FRET’ experiments and the development of low-cost quantum computers.

Speaker: Sourabh Singh Chauhan, University of Minnesota
3:35 pm:
Speaker: Stacy McGaugh, Case Western
Subject: Dynamical Regularities in Galaxies and their Implications for Dark Matter
Refreshments in atrium after the Colloquium.

The flat rotation curves of galaxies were a surprising observation that helped establish the dark matter paradigm. Flat rotation curves are only the first of a series of striking regularities in the dynamics of galaxies. The amplitude of the flat rotation speed is not random; it correlates strongly with the mass observed in stars and gas (the baryonic Tully-Fisher relation). At the centers of galaxies, the dynamical surface density correlates with the observed surface brightness of stars (the central density relation). At all observed radii, the observed centripetal acceleration correlates with the acceleration predicted by the observed distribution of baryons (the radial acceleration relation). These empirical relations inform our thinking about the missing mass problem in ways that were not available when the current paradigm was established.

Faculty Host: J. Woods Halley
4:35 pm:
Climate and Diversity Committee Meet and Greet. 4:30 - 6:00 Drop In in Tate Lower Atrium (near B-50) right after the colloquium
Subject: Introduction and Information gathering session
Come and meet your Climate and Diversity Committee and reps from student groups. Find out what we do, connect with your colleagues, provide feedback and suggestions. Refreshments will be served.

Friday, December 7th 2018
12:20 pm:
Speaker: Nicholas Lewellyn
Subject: Infinite-randomness fixed point of quantum superconductor-metal transitions
Speaker: K. S. Babu (Oklahoma State U.)
Subject: Fermion masses, proton decay and the strong CP problem in SUSY SO(10)

In this talk, I shall present new results on fermion masses and mixings and proton decay in the context of renormalizable SUSY SO(10) models. Difficulties with the minimal model are avoided by enlarging the symmetry breaking sector with a 54. Consistent fermion mass spectrum is obtained, including the neutrino sector. A mini-split SUSY spectrum is suggested by proton decay constraints, which is compatible with pure gravity mediation. A successful implementation of the Peccei-Quinn symmetry will be presented, in which case the model becomes compatible with proton lifetime with TeV scalars.

Speaker: Tracy Clarke, Naval Research Lab
Subject: Low Frequency Astrophysics: From FRBs to Surveys

Low frequency interferometry is re-emerging as powerhouse for astrophysical studies. Hot-topic areas include the search for extrasolar planets, detecting fingerprints of the first stars, localizing and identifying the hosts of fast radio bursts (FRBs), and tracing shocks, turbulence and feedback in clusters of galaxies. In this talk I will discuss the revitalization of low frequency interferometry, including a discussion of current interferometers and capabilities. I will specifically highlight a new commensal low frequency system we developed on the NRAO VLA that provides data 24/7 from this powerful interferometer. I will discuss several individual programs where low frequencies play a leading role in the research and end with a look to the future of low radio frequency with ngLOBO (a complementary system to the ngVLA) and the SKA. Authors: T. E. Clarke (Naval Research Laboratory)

3:35 pm:
Speaker: Roger Stuewer, History of Science and Technology, Department University of Minnesota
Subject: From the Old to the New World of Nuclear Physics, 1919–1939
Refreshments served at 3:15 p.m.

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.

4:40 pm:
Speaker: Paul Crowell, Condensed Matter

Monday, December 10th 2018
12:15 pm:
Speaker: Rich Ormiston, UMN
Subject: Extending the reach of gravitational-wave detectors with machine learning

With the advent of gravitational-wave astronomy, techniques to extend the reach of gravitational- wave detectors are desired. In addition to the stellar mass black hole and neutron star mergers already detected, many more are below the surface of the noise, available for detection if the noise is reduced enough. One method for noise reduction applies machine learning algorithms to gravitational-wave detector data and auxiliary channels on-site to reduce the noise in the time-series due to instrumental artifacts. Given realistic assumptions about coupling mechanisms, we are able to reduce the noise floor, leading to detector sensitivity improvements. This framework is generic enough to subtract both linear and non-linear coupling mechanisms, and learn about the mechanisms which are not currently understood to be limiting detector sensitivities. We discuss lessons learned and how this work can be generalized to other time series regression analyses in all areas of science.

Faculty Host: Vuk Mandic
12:30 pm:
FTPI Seminar in Tate 301-20
Speaker: Pavel Pylyavskyy, University of Minnesota, Dept. of Mathematics
Subject: Ising model and the positive orthogonal Grassmannian

Ising model is a classical model for ferromagnetism in statistical mechanics. In a joint work with Pavel Galashin we completely describe by inequalities the set of boundary correlation matrices of planar Ising networks embedded in a disk. Specifically, we give a simple bijection between such correlation matrices and points in the totally nonnegative part of the orthogonal Grassmannian, which has been introduced recently in the study of the scattering amplitudes of ABJM theory. Under our correspondence, Kramers--Wannier's high/low temperature duality transforms into the cyclic symmetry of the Grassmannian. We also show that the edge parameters of the Ising model for reduced networks can be uniquely recovered from boundary correlations, solving the inverse problem.

Faculty Host: Alex Kamenev

Tuesday, December 11th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.
1:25 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.

Wednesday, December 12th 2018
09:05 am:
Methods of Experimental Physics Poster Session in Tate Hall Basement Atrium
Join us for a poster session recognizing the work this semester's MXP II students have accomplished this Fall.
1:25 pm:
Speaker: Brian Skinner, MIT
Subject: Percolative Phase Transition in the Dynamics of Quantum Entanglement

When left unobserved, many-body quantum systems tend to evolve toward states of higher entanglement. Making a measurement, on the other hand, tends to reduce the amount of entanglement in a many-body system by collapsing one of its degrees of freedom. In this talk I discuss what happens when a many-body quantum system undergoes unitary evolution that is punctuated by a finite rate of projective measurements. Using numerical simulations and theoretical scaling arguments, we show that for a 1D spin chain there is a critical measurement rate separating two dynamical phases. At low measurement rate, the entanglement grows linearly with time, producing a volume-law entangled state at long times. When the measurement rate is higher than the critical value, however, the entanglement saturates to a constant as a function of time, leading to area-law entanglement. We map the dynamical behavior of the entanglement onto a problem of classical percolation, which allows us to obtain the critical scaling behavior near the transition. I briefly discuss generalizations of our result to higher dimensions, and its implications for the difficulty of simulating quantum systems on classical computers.

Faculty Host: Boris Shklovskii
There will be no seminar this week.

Thursday, December 13th 2018
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week.
3:35 pm:
There will be no colloquium this week

Friday, December 14th 2018
10:00 am:
Thesis Defense in Peik Hall 325
Speaker: Miranda C. P. Straub, Curriculum and Instruction Department.
Subject: An Empirical Model of Physics Instructors’ Beliefs about the Purpose, Actions, and Context of Doing Homework
This is public portion of Ms. Straub's Thesis Defense. Her advisors are Leon Hsu and Ken Heller.

Over the past half century, researchers and curriculum developers studying physics education have created dozens of innovative curricula and educational tools, broadly referred to as research-based instructional strategies (RBIS), to fit almost any classroom situation. These include cooperative problem solving (Heller & Hollabaugh, 1992; Heller, Keith, & Anderson, 1992), Physics By Inquiry (McDermott, Shaffer, & Rosenquist, 1996), Investigative Science Learning Environment (ISLE) (Etkina & Van Heuvelen, 2007), Studio Physics (Cummings et al., 1999), and Peer Instruction (Crouch & Mazur, 2001) among others. However, the rate of adoption of RBIS remains relatively low. A national survey of post-secondary physics instructors in 2012 showed that only half of physics instructors have ever implemented any RBIS in their classrooms, and many of them ceased to do so after implementation difficulties (Henderson & Dancy). Why aren’t these effective strategies being implemented at larger rates? Part of removing barriers to RBIS adoption may be understanding what instructors believe about how students learn.

In order to answer a small portion of this question, I studied physics instructors’ beliefs about homework. This study is taken up in two parts. First, I analyzed 25 interviews with physics instructors from various types of institutions in Minnesota (Yerushalmi et al., 2007; Henderson, et al., 2007). Second, I used the themes from the interview analysis to create a survey, which was then sent to physics instructors in the state of Minnesota. Using both the interview analysis and the survey responses, I created an empirical model of physics instructors’ beliefs about homework. There were four main results. First, there is agreement that the goals of doing homework are to learn problem solving and physics principles. Second, homework is seen as necessary for learning physics by a strong majority of instructors, but it is not seen as sufficient for learning. Third, there is a limited number of tasks or actions that instructors believe that students should do while they are solving problems. Fourth, there is evidence that physics instructors fall onto a continuum of beliefs regarding how students should approach solving problems on their homework. On one end of this continuum, instructors believe students should follow an algorithmic process that includes the steps to solving any problem. On the other end of the continuum, instructors believe students should have a more open approach to solving problems where they consider all the tools and principles available to them in order to make decisions about how to solve a problem. These results can inform creators of curriculum and professional development as they try to reach out and connect with instructors and perhaps change their beliefs and practice.

12:20 pm:
Speaker: Daniel Shaffer
Subject: Interplay between Rashba Spin-Orbit Coupling, Magnetic Field, and Topological Superconductivity in Monolayer NbSe_2
12:30 pm:
There will be no seminar this week.
Speaker: Rafaella Margutti, Northwestern University
Subject: Discovery frontiers in the new era of Time Domain Multi-Messenger Astrophysics

New and improved observational facilities are sampling the night sky with unprecedented temporal cadence and sensitivity across the electromagnetic spectrum. This exercise led to the discovery of new types of astronomical transients and revolutionized our understanding of phenomena that we thought we already knew. In this talk I will review some very recent developments in the field that resulted from the capability to acquire a true panchromatic view of the most extreme stellar deaths in nature.

3:35 pm:
There will be no colloquium this week
4:40 pm:
There will be no seminar this week.

Tuesday, December 18th 2018
11:15 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.

Monday, December 24th 2018
08:00 am:

Tuesday, December 25th 2018
08:00 am:

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