Physics and Astronomy Calendar

semester, 2018


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.

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.
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.
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
Subject:  Instructor beliefs about homework

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.

Faculty Host: Vlad Pribiag
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.
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.

2:30 pm:
Speaker: David Radice, Princeton University
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
Speaker: Yassin Haddad, Imperial College London
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.

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.

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.

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

t 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
To be announced.

Thursday, March 1st 2018
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.

Speaker: Evan Tyler
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
To be announced.
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
Faculty Host: Thomas W. Jones
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:
To be announced.
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.


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
Speaker: Stephen Martin (Northern Illinois U.)
Subject: TBA
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

Thursday, March 15th 2018
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:
Speaker: Liliya Williams, UMN

Wednesday, March 21st 2018
1:25 pm:
Speaker: Pablo Jarillo-Herrero, MIT
Subject: TBD
Faculty Host: Vlad Pribiag

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: TBD
Faculty Host: Vlad Pribiag

Friday, March 23rd 2018
10:00 am:
Speaker: Daniel Sheehy, LSU
Faculty Host: Rafael Fernandes
Speaker: Gokce Basar (U. Illinois, Chicago)
Subject: TBA
Speaker: Dr. Jordan Stone, U. Arizona
Faculty Host: Charles E. Woodward
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.


Tuesday, March 27th 2018
2:30 pm:
Speaker: Vladimir Skokov, Brookhaven National Laboratory
Subject: TBD
Candidate for the Nucear Theory Assistant Professor position
Speaker: Michael Fogler, University of California, San Diego
Faculty Host: Boris Shklovskii

Wednesday, March 28th 2018
1:25 pm:
Speaker: Paul Canfield (Iowa State)
Subject: TBD
Faculty Host: Martin Greven
3:30 pm:
Space Physics Seminar in Physics 201-20
Speaker: Barry Mauk, APL
Subject: TBD
Faculty Host: Robert Lysak

Thursday, March 29th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Casim Sarkar, Professor of Biomedical Engineering, 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
Speaker: Hooman Davoudiasl (Brookhaven)
Subject: TBA
Speaker: Lou Stolger, Space Telescope
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.


Monday, April 2nd 2018
12:15 pm:
Speaker: Matt Gomer, UMN
Faculty Host: Liliya L.R. Williams

Wednesday, April 4th 2018
1:25 pm:
Speaker: Sung-Sik Lee (Perimeter Institute)
Subject: TBD
Faculty Host: Andrey Chubukov

Thursday, April 5th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: James M. Carothers, Department of Bioengineering, University of Wisconsin

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
3:35 pm:
Speaker: Alessandra Corsi, Texas Tech
Subject: TBD
Faculty Host: Vuk Mandic

Friday, April 6th 2018
Speaker: Elena Caceres (U. Texas, Austin)
Subject: Rotating Traversable Wormholes
Speaker: No colloquium this week.
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.


Monday, April 9th 2018
12:15 pm:
Speaker: Jose Diego, Consejo Superior de Investigaciones Cientificas, CSIC
Faculty Host: Patrick Kelly

Wednesday, April 11th 2018
1:25 pm:
Speaker: Xiaojia Wang (University of Minnesota)
Subject: TBD
Faculty Host: Paul Crowell

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
Speaker: Karl Young
3:35 pm:
Speaker: Doug Glenzinski, Fermilab
Subject: TBD
Faculty Host: Dan Cronin-Hennessy

Friday, April 13th 2018
Speaker: Kristian Jensen (San Francisco State U.)
Subject: TBA
Speaker: T. Rivera-Thorsen, Institute of Theoretical Astrophysics
Faculty Host: M. Claudia Scarlata
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.


Monday, April 16th 2018
12:15 pm:
Speaker: Hugh Dickinson, UMN

Wednesday, April 18th 2018
7:00 pm:
Kaufmanis Public Lecture in McNamara Alumni Center
Speaker: Victoria Kaspi, McGill University
Subject: Astronomy's Newest Extragalactic Mystery: Fast Radio Bursts!

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: John Phillips
3:35 pm:
Speaker: Victoria Kaspi, McGill University.
Subject: TBD
Faculty Host: Andrey Chubukov

Friday, April 20th 2018
Speaker: Nobuchika Okada (U. Alabama)
Subject: TBA
Speaker: No colloquium - See info for the Kaufmanis Public Lecture on the 18th
Speaker: Roberta Humphreys, Minnesota Institute for Astrophysics, University of Minnesota
Subject: "Margaret Burbidge, and the Annie Jump Cannon Award or How I Met Vera Rubin -- a Personal and Scientific Recollection"
Refreshments served at 3:15 p.m.

Monday, April 23rd 2018
12:15 pm:
Speaker: Qi Wen, UMN
Faculty Host: Shaul Hanany

Thursday, April 26th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Gianluigi Veglia, Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota
Speaker: Sourabh Chauhan
3:35 pm:
Speaker: John Bush, MIT
Subject: TBD
Faculty Host: J. Woods Halley

Friday, April 27th 2018
Speaker: Mustafa Amin (Rice U)
Subject: TBA
Speaker: Dr. Christian Veillet, Large Binocula Telescope Observatory (LBTO)
Faculty Host: Charles E. Woodward
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.


Monday, April 30th 2018
12:15 pm:
Faculty Host: M. Claudia Scarlata

Thursday, May 3rd 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Ibrahim Cisse, Department of Physics, Massachusetts Institute of Technology
3:35 pm:
Speaker: Jeffrey Bub, Maryland
Subject: TBD
Faculty Host: Michel Janssen

Friday, May 4th 2018
Friday, May 4 - Sunday, May 6 2018
Faculty Host: Alex Kamenev
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. Silva Protoppa, U. Maryland
Faculty Host: Charles E. Woodward

Saturday, May 5th 2018
Friday, May 4 - Sunday, May 6 2018
Faculty Host: Alex Kamenev

Sunday, May 6th 2018
Friday, May 4 - Sunday, May 6 2018
Faculty Host: Alex Kamenev

Thursday, May 10th 2018
10:10 am:
Biophysics Seminar in 120 PAN
Speaker:  Hyun Youk, Kavli Institute of Nanoscience, TU Delft, Netherlands

Wednesday, May 16th 2018
Wednesday, May 16 - Saturday, May 19 2018
Faculty Host: Andrey Chubukov

Thursday, May 17th 2018
Wednesday, May 16 - Saturday, May 19 2018
Faculty Host: Andrey Chubukov

Friday, May 18th 2018
Wednesday, May 16 - Saturday, May 19 2018
Faculty Host: Andrey Chubukov

Saturday, May 19th 2018
Wednesday, May 16 - Saturday, May 19 2018
Faculty Host: Andrey Chubukov

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