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Events During the Week of December 4th through December 11th, 2016

Monday, December 5th, 2016

Atomic Physics Seminar
High Energy Lasers at the Extreme Light Infrastructure
Time: 2:00 pm
Place: 5310 Chamberlin Hall
Speaker: Tyler Green, ELI project at the Czech Republic.
Abstract: High energy short pulse lasers are useful tools for probing the structure and dynamics of materials and accelerating particles. The European Union is investing in a network of laser centers focused on fundamental research called the Extreme Light Infrastructure (ELI). ELI hopes to allow the investigation of new regimes of laser-matter interaction with multi-petawatt laser pulses and unprecedented repetition rates. In this talk I will present one of the facilities currently under development in Prague, Czech Republic. While an overview of the laser systems under development will be given, the primary focus of the talk will be on current techniques and principles of high energy laser amplification.
Host: Yavuz
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Tuesday, December 6th, 2016

Chaos & Complex Systems Seminar
2016 Polling in Nation and State: A scorecard
Time: 12:05 pm - 1:00 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: Charles Franklin, Law and Public Policy and Director of the Marquette University Law School Poll
Abstract: How did the pre-election polls of 2016, at both national and state levels, perform? What did we learn about the dynamics of the campaign and the issues affecting public polling? How accurate were the polls and were some methods better than others?
Host: Clint Sprott
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Theory Seminar (High Energy/Cosmology)
Search For Dark Matter In Terms of Dark Bound States
Time: 3:30 pm
Place: 5280 Chamberlin
Speaker: Yue Zhang, Northwestern
Abstract: Understanding the nature of dark matter is an open question of central importance to particle physics and cosmology. In this talk, I discuss a model where the dark matter is a fermion charged under a dark U(1) gauge symmetry and its interactions are mediated by a massive dark photon. I will summarize the current status in the search for such a dark sector. The main focus of this talk is on the non-perturbative effects in particular dark matter bound states, which could have strong impact on the interpretation of existing experimental results and lead to new channels for the future search.
Host: Yang Bai
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Wednesday, December 7th, 2016

Department Meeting
Closed meeting to discuss personnel matters
Time: 12:15 pm - 1:15 pm
Place: 5310 Chamberlin Hall
Closed meeting to discuss personnel matters—pursuant to Section 19.85(1)(c) of the Wisconsin Open Meetings Law
Closed to all but tenured faculty
Host: Albrecht Karle
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Thursday, December 8th, 2016

R. G. Herb Condensed Matter Seminar
Universal transport at the edge: Disorder, interactions, and topological protection
Time: 10:00 am
Place: Chamberlin 5310
Speaker: Matthew Foster, Rice University
Abstract: Topological insulators and superconductors provide condensed matter realizations of the holographic principle: a topological property of the bulk translates into an anomalous time-reversal symmetry at the material surface. This symmetry underlies "topological protection" of the edge or surface states. Protection from disorder effects (Anderson localization) is particularly nontrivial, because surfaces are low dimensional. While this was previously understood for noninteracting models of edge and surface states, the more complicated problem of combined disorder and interaction effects had not been addressed until recently. I will discuss two different examples of universal edge or surface transport that arise in the presence of both. First, I will consider the edge states of 2D topological insulators with Rashba spin-orbit coupling (RSOC). With RSOC, disorder induces a backscattering term in the edge theory. We have shown that transport remains perfectly ballistic in a model that incorporates this term and interactions. The solution involves a mapping to spin 1/2 moment that executes perfect adiabatic evolution in a random magnetic field. [1] Second, I will discuss the surface states of 3D topological superconductors, and explain why we predict universal surface thermal and (if conserved) spin conductivities. The solution combines various nonperturbative and/or exact methods including conformal field theory, the Finkel'stein non-linear sigma model, and numerics. [2,3] I will also show how disorder enhances topological protection for surface states of recently introduced [4] model spin-3/2 topological superconductors, which may have applications to ultracold atoms or Half-Heusler compounds.

Refs:
[1] H.-Y. Xie, H. Li, Y.-Z. Chou, and M. S. Foster, PRL 116, 086603 (2016)
[2] H.-Y. Xie, Y.-Z. Chou, and M. S. Foster, PRB 91, 024203 (2015)
[3] M. S. Foster, H.-Y. Xie, and Y.-Z. Chou, PRB 89, 155140 (2014)
[4] W. Yang, Yi Li, and C. Wu, PRL 117, 075301 (2016)
Host: Alex Levchenko
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Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:15 pm - 1:15 pm
Place: 5242 Chamberlin Hall
Abstract: Please visit the following link for more details:href="http://cmb.physics.wisc.edu/journal/index.html">http://cmb.physics.wisc.edu/journal/index.html
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Amol Upadhye (aupadhye@wisc.edu).
Host: Amol Upadhye
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Astronomy Colloquium
The Turbulent Origin of Stars
Time: 3:30 pm - 5:00 am
Place: 4421 Sterling Hall, Coffee and cookies 3:30 pm, Talk at 3:45PM
Speaker: Phillip Chang, UW Milwaukee
Abstract: Recent numerical experiments on the star formation rate on small scales find that the star formation rate is much faster than the Kennicutt-Schmidt law which well-characterizes star formation on galactic scales, and also shows that star formation accelerates with time. Motivated by these results, I will discuss a new dynamical theory of star formation in a turbulent medium that seeks to explain these observed numerical results. I will survey the various theories of star formation and their shortcomings. I will then discuss how we extend previous theories of collapse by considering turbulence as a dynamical variable and closing the fluid equations with a new form of the energy equation. The resulting theory explains these previous numerical results and makes a few predictions that have recently been numerically verified as well as some numerical surprises. I will discuss the implications of this theory on observations.
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Friday, December 9th, 2016

Plasma Theory Seminar
tbd
Time: 2:15 pm - 3:45 pm
Place: 5280 Chamberlin hall
Speaker: Chad Williams
Abstract: tbd
Host: Daniel J. Den Hartog
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Physics Department Colloquium
Holiday Colloquium
Time: 4:30 pm - 6:00 pm
Place: 2103 Chamberlin Hall
Host: 3rd year graduate students
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