This Week at Physics

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This Week at Physics

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Events During the Week of November 29th through December 6th, 2015

Monday, November 30th, 2015

Plasma Physics (Physics/ECE/NE 922) Seminar
Time: 12:00 pm
Place: 2241 Physics Bldg
Speaker: Christopher Hansen, University of Washington
Abstract: In MagnetoHydroDynamic (MHD) simulations of Magnetic Confinement Fusion (MCF) experiments the first wall is often treated as a continuous, symmetric surface. However, even in machines with a high degree of plasma symmetry, the true first wall is complex. Perforations required for diagnostic, heating, and current injection ports and localized stabilizing plates all effect induced-currents in the wall, modifying the behavior of resistive wall modes and scrape-off layer currents.

The PSI-Tet code is a new 3D extended MHD code based on an unstructured tetrahedral grid that allows arbitrary device geometry to be captured. This code employs a high order finite element method using a novel discretization for magnetic flux based on Nedelec basis functions. A fully implicit centered time advance (Crank-Nicolson) is used and solved with a multigrid preconditioned Newton-Krylov method. In this talk progress and results will be presented from two applications of PSI-Tet: 1) Detailed validation studies of the HIT-SI experiment with self-consistent modeling of plasma dynamics in the helicity injectors. Results will be compared to experimental data and NIMROD simulations that model the effect of the helicity injectors through boundary conditions on an axisymmetric domain. 2) Simulations of external kink dynamics in the HBT-EP experiment with different wall configurations, focusing on toroidal asymmetries in the adjustable conducting wall. A brief description of the PSI-Tet code will also be presented focusing on unique features of the code.
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Tuesday, December 1st, 2015

Chaos & Complex Systems Seminar
Effects of Facebook self-presentation on individual and relational well-being
Time: 12:05 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: Catalina Toma, UW Department of Communication Arts
Abstract: Facebook invites users to compose detailed personal profiles, where they describe their activities, interests, and values; express daily thoughts and musings; and articulate "friendships" with other users in the system. Research shows that users engage in copious yet careful self-disclosure in their own profiles, and that they frequently provide positive feedback ("likes," "comments") to friends' postings. What are the psychological implications of constructing and engaging with this socially connected, online version of self? I will first discuss the emotional well-being effects of engaging with one's own profile. In a suite of studies, we found that users experience self-affirmation, increased positive affect, and increased self-esteem after examining their own profiles. They also gravitated towards these profiles when feeling badly about themselves, in an effort to repair feelings of self-worth. I will then discuss the effects of profile self-presentation on users' romantic relationships. Data show that users who publicly declare their involvement with a romantic partner (by listing themselves as "in a relationship," posting couple photographs, etc.) experience increased commitment towards that partner and are less likely to break up after 6 months. I will end by discussing future research avenues on the psychological effects of Facebook self-presentation.
Host: Sprott
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Theory Seminar (High Energy/Cosmology)
Membranes, monodromy, and the weak gravity conjecture
Time: 3:30 pm
Place: 5280 Chamberlin Hall
Speaker: Miguel Montero, Universidad Autonoma de Madrid
Abstract: Instantons coming from the Weak Gravity Conjecture (WGC) often
raise issues with large field inflationary models coming from axions.
These issues are famously absent for monodromic inflationary models, in
which the axion rolls many times its fundamental period. However, a
different version of the WGC, the 3-form WGC, predicts the existence of
membranes which can mediate fast transitions along the axion potential.
I will discuss the validity of the 3-form WGC, how typical monodromy
inflation models are not threatened by membrane-mediated transitions,
and some other details of membrane physics.
Host: Pablo Soler
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Wednesday, December 2nd, 2015

No events scheduled

Thursday, December 3rd, 2015

R. G. Herb Condensed Matter Seminar
Electromagnetic coupling of spins and pseudospins in bilayer graphene
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Prof. Roland Winkler, Northern Illinois University
Abstract: We present a detailed theoretical study of bilayer-graphene's
electronic properties in the presence of electric and magnetic
fields. Using group-theoretical methods, we derive an invariant
expansion of the Hamiltonian for electron states near the K point of
the Brillouin zone. In contrast to known materials, including
single-layer graphene, any possible coupling of physical quantities
to components of the external electric field has a counterpart where
the analogous component of the magnetic field couples to exactly the
same combination of quantities. For example, a purely electric spin
splitting appears as the magneto-electric analogue of the familiar
magnetic Zeeman spin splitting. The measurable thermodynamic
response induced by magnetic and electric fields is thus completely
symmetric. The Pauli magnetization induced by a magnetic field
takes exactly the same functional form as the polarization induced
by an electric field. Our findings thus reveal unconventional
behavior of spin and pseudospin degrees of freedom induced by
external fields. Although they seem counterintuitive, our findings
are consistent with fundamental principles such as time reversal
symmetry. For example, only a magnetic field can give rise to a
macroscopic spin polarization, whereas only a perpendicular electric
field can induce a macroscopic polarization of the
sublattice-related pseudospin degree of freedom characterizing the
intravalley orbital motion in bilayer graphene. These rules
enforced by symmetry for the matter-field interactions clarify the
nature of spins versus pseudospins. While our theoretical arguments
use bilayer graphene as an example, they are generally valid for any
material with similar symmetries. The unusual equivalence of
magnetic and electric fields discussed here can provide the basis
for designing more versatile device architectures for creating
polarizations and manipulating the orientation of spins and
Host: Joynt
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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 Amol Upadhye (
Host: Amol Upadhye
Host: Amol Upadhye
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Astronomy Colloquium
Star Formation in HI Dominated Environments
Time: 3:30 pm
Place: 4421 Sterling Hall, Coffee and Cookies 3:30, Talk 3:45 PM
Speaker: Jennifer Donavan Myer, NRAO
Abstract: I will discuss recent work on star forming, HI-dominated environments from nearby, low-mass dwarf galaxies to extended ultraviolet (XUV) disks. In both cases, stars are forming at low levels -- requiring interstellar media capable of doing so -- but the gas columns and molecular fractions in these regions can differ substantially from those in the main disks of normal, star forming galaxies. I'll present some ongoing studies of the gas available for stars to form in these very different environments and discuss their broader context by comparing to more typically studied star forming gas. Finally, I will address the evolutionary context of these environments, as they are great examples of the ways in which atomic gas affects the ongoing evolution of galaxies of all sizes.
Host: Matt Haffner, Astronomy Dept
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Friday, December 4th, 2015

Physics Department Colloquium
Quantum Electromechanics
Time: 3:30 pm
Place: 2241 Chamberlin Hall (Coffee & Cookies at 3:15pm)
Speaker: Konrad Lehnert, University of Colorado Boulder
Abstract: What is the largest object whose motion requires a quantum, rather than classical description? This question lies at the very foundation of quantum mechanics. At the same time, investigating this question experimentally is a highly practical endeavor of isolating an object from its environment and taming uncontrolled sources of noise. Establishing quantum control over large objects impacts a host of potential quantum technologies, such as quantum sensing, communication, and computation. In this talk, I will describe our recent success in controlling the quantum state of macroscopic mechanical oscillators and our progress in using this result to develop quantum information processing devices that exploit the unique properties of mechanical systems. In particular, we are developing a device that uses a mechanical oscillator to transfer information noiselessly between electrical and optical domains. In the quantum regime, this device would enable a communication network with information security guaranteed by physical laws of nature.
Host: Robert McDermott
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