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This Week at Physics

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Events During the Week of November 9th through November 15th, 2014

Monday, November 10th, 2014

Plasma Physics (Physics/ECE/NE 922) Seminar
3D Modeling of RF Antennas, Sheaths, and Slow Waves in Time Domain
Time: 12:00 pm
Place: 2535 Engineering Hall
Speaker: David Smithe, Tech-X Corporation
Finite difference time domain simulation tools offer unique capability for the study of RF antennas in fusion-scale experiments, because of their traditional focus on accurate detailed representation of 3D geometry.

This talk will present our efforts to apply such a code to the modeling of antennas on MST, NSTX, CMod, and ITER. RF sheaths on or near the antenna are believed to be responsible for impurity production, a major concern for fusion experiments. These same sheath effects are also key to producing non-thermal electron populations which maintain ionization in some industrial plasmas.
The talk will show how we use sub-grid models to represent the RF and rectified sheath, and how we plan to combine this with test particles to model non-thermal physics. Finally, while performing such simulations, an observation of strong slow-wave excitation in a thin layer near the antenna has also led to questions of whether such waves might be a contributor to parasitic losses from these antennas, e.g., in NSTX. The talk will discuss this hypothesis, and on-going modeling efforts aimed at better understanding it.
Host: CPTC
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Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:15 pm
Place: 5242 Chamberlin Hall
Abstract: Please visit the following link for more details:
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 Le Zhang (lzhang263@wisc.edu)
Host: Peter Timbie
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Council Meeting
Time: 4:00 pm
Place: 2314 Chamberlin (Chair's Conference Room)
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Tuesday, November 11th, 2014

Chaos & Complex Systems Seminar
The narrative structure of the default mode network and REM dreaming
Time: 12:05 pm
Place: 4274 Chamberlin Hall (Refreshments will be served)
Speaker: Art Schmaltz, Prairie State College
Abstract: This presentation will build upon the structural architecture of the default mode network outlined here by Deric Bownds on September 9th. My focus will be on the functional aspects of the human brain's default mode network.

I will argue that the default mode network is an evolved brain system with adaptive functions.
The default mode network and REM dreaming-- both "hard wired" brain systems-- are complementary and work in concert with each other.
Both systems are intrinsically intersubjective and variational praxis orientated.
Both systems create new narratives, or novel behavioral scripts: an ongoing eco-hermeneutics for optimal adaptation to ever shifting environments.
Host: Clint Sprott
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Theory Seminar (High Energy/Cosmology)
Aspects of Lepton-Flavored Dark Matter
Time: 3:00 pm
Place: 5280 Chamberlin Hall
Speaker: Can Kilic, The University of Texas at Austin
Abstract: All matter in the Standard Model (SM) appears in three generations, with an intricate flavor structure the origin of which is not well understood. This motivates the question whether distinct phenomenological features arise if dark matter (DM) also has a non-trivial flavor structure. In this talk I will focus on the possibility where the flavor structure of DM is linked to SM flavor in the lepton sector, and review the experimental signatures of this scenario. In particular, I will argue that the generation of a lepton asymmetry at a high energy scale can also produce a DM asymmetry, which can strongly affect the sensitivity of direct detection experiments, and I will present novel signatures that can appear at colliders and in indirect detection experiments for lepton-flavored DM.
Host: Ran Lu
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Wednesday, November 12th, 2014

Department Meeting
Time: 12:15 pm
Place: 5310 Chamberlin Hall
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Thursday, November 13th, 2014

R. G. Herb Condensed Matter Seminar
Generalized Tunneling Model (GTM) for Two Level System (TLS) in amorphous materials and its predictions for their dephasing and the noise in superconducting microresonators
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Lara Faoro, Universites Paris 6 et 7 and Rutgers University
Abstract: Thin film high quality superconductor microresonators are important for a number of diverse applications that range from quantum computation to submillimeter and far-infrared astronomy. The performance of these devices has improved dramatically over the past decades and resonator quality factors above 10^6 are now routinely achieved using single-layer structures deposited on high-quality low-loss crystalline substrate. Achieving high-quality factors requires minimizing all potential sources of dissipation and noise. One prominent source of dissipation in microresonators has been found to be Two Level Systems (TLSs) in thin amorphous dielectric surface layers of the microresonators. These TLS are also responsible for an excess frequency noise (jitter) in the resonators. TLS in amorphous materials are usually described by the Standard Tunneling Model (STM). In this theory, TLS are represented as independent quantum two level systems with constant distribution of low energy states. Unfortunately, STM fails to explain the data of noise in the superconducting microresonators so a consistent model for the noise due to TLS in superconducting resonators remains an open issue.
In this talk we shall first review data of recent experiments performed on high quality superconducting microresonator where low frequency noise spectra have been studied in varying temperature and different applied power and argue that the data are inconsistent with the STM. We shall then propose a new model, the Generalized Tunneling Model (GTM) which includes strong interactions between TLS and a slow power law dependence of their density of states. We show that the predictions of this model are in a perfect agreement with the recent studies of the noise in high quality superconducting resonators. The predictions also agree with the temperature dependence of the TLS dephasing rates observed in phase qubits. Finally, we discuss the origin of the universal dimensionless parameter that controls the interaction between TLS in glasses and show that it is consistent with the assumptions of the GTM.
Host: McDermott
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Atmospheric Neutrinos
Time: 3:00 pm
Place: 5280 Chamberlin Hall
Speaker: Professor Tom Gaisser, University of Delaware
Host: Karle
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Astronomy Colloquium
"Faint Lyman-alpha Emitters and the Reionization of the Universe"
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Alan Dressler, Carnegie Observatories
Abstract: There is general agreement that the photons that reionize the universe beginning at z ~ 12 are produced by young, starforming galaxies, however, the brighter galaxies that are readily detected at z > 5 fall well short of supplying the required flux of Lyman-continuum photons. I will describe an 8-year spectroscopic search with IMACS on Magellan for the faintest Lyman-alpha emitters (LAEs) at z= 5.7. Our study has pushed the detection limit an order-of-magnitude fainter than the prominent narrow-band-imaging surveys,leading to the first robust measurement of the faint-end-slope of the luminosity function. We find that LAEs make a substantial, perhaps dominant, contribution in the final stages of reionization. These young, low-mass galaxies -- more numerous than today's L* galaxies -- are likely to play an important role in the assembly of early galaxies and their chemical enrichment of the early IGM.
Host: Professor Jay Gallagher
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Graduate Introductory Seminar
Nuclear Physics and Astrophysics
Time: 4:30 pm
Place: 5280 Chamberlin Hall
Speaker: Balantekin
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Friday, November 14th, 2014

Physics Department Colloquium
Neutrinos... Going International: Towards a New Understanding of the Quantum Universe
Time: 3:30 pm
Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
Speaker: Dr. Nigel Lockyer, Director, Fermi National Accelerator Laboratory
Abstract: Neutrinos are the most numerous massive particles in the universe. The masses are tiny and unknown, which neutrino is heaviest is unknown, and whether the neutrino is a Majorana particle is unknown. We do not know how the Higgs field provides mass to the neutrino. Indeed, the complete chapter on mass and fermion family patterns has yet to be written and at the heart of this discussion is the ubiquitous neutrino. Neutrino masses influence the cosmic microwave background polarization. Neutrinos are a possible source of CP violation in the universe that may play a role in generating the matter excess in the universe. Each of these questions is developing as one of the main quests in particle physics throughout the world. As Fermilab develops its plan for the next two decades with partners around the world, the neutrino will be front and center.
Host: Francis Halzen
Poster: http://www.physics.wisc.edu/twap/posters/2014/3340.pdf
Video: http://www.physics.wisc.edu/vod/2014/11/14.html
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