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This Week at Physics

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Events During the Week of May 6th through May 13th, 2012

Monday, May 7th, 2012

Plasma Physics (Physics/ECE/NE 922) Seminar
Magnetic Reconnection in Plasmas; a Celestial Phenomenon in the Laboratory
Time: 12:05 pm
Place: 2535 Engineering Hall
Speaker: Prof. Jan Egedal, MIT
Abstract: Coronal mass ejections from the sun are the most explosive events that occur
in our solar system. Closer to home, the aurora borealis is one of the most
spectacular, naturally occurring, light show at high latitudes on the Earth. Both
of these large scale events are driven by magnetic reconnection in plasmas.
The spontaneous rearrangement of magnetic field topology provides the
enormous energy needed for these celestially magnificent and diverse
phenomena.
For more than fifty years, magnetic reconnection has been a fascinating topic of
research in plasma physics. While we do not fully understand the process of
reconnection, significant progress has been made in the past decade through
detailed analysis of laboratory experiments, and computer simulations. The
Versatile Toroidal Facility at MIT is one such experiment dedicated to the study
of magnetic reconnection. In this talk I will describe the recent experimental
observations which have led to a new theoretical paradigm for magnetic
reconnection. Large scale computer simulations support the theoretical and
experimental results. The analysis of experimental observations in a laboratory
device has led to a comprehensive understanding of data from spacecraft
observing celestial reconnection events in the EarthaEuroTMs magnetosphere.
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Condensed Matter Theory Group Seminar
The finite temperature phase diagram for Kitaev-Heisenberg model
Time: 4:30 pm
Place: 5310 Chamberlin
Speaker: Craig Price, UW-Madison
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Tuesday, May 8th, 2012

Chaos & Complex Systems Seminar
Are you holding your breath? - Structures of arousal and calm
Time: 12:05 pm
Place: 4274 Chamberlin
Speaker: Deric Bownds, UW Department of Zoology
Abstract: This talk discusses some of the structures of calm and arousal - whether we are chilled out or losing it. The material is cooked down to four sections, that (1), note some structures regulating calm and arousal (2), list some brain and body correlates (3) consider the definition of the self that stresses or calms. (4) discuss bottom-up and top-down regulators under some voluntary control that can alter the balance between calm and arousal.
Host: Sprott
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"Physics Today" Undergrad Colloquium (Physics 301)
Askaryan Radio Array at the South Pole
Time: 1:20 pm
Place: 2223 Chamberlin
Speaker: Michael DuVernois, University of Wisconsin IceCube Project
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Wednesday, May 9th, 2012

No events scheduled

Thursday, May 10th, 2012

R. G. Herb Condensed Matter Seminar
Shedding Light on Artificial Quantum Materials and Interfaces by Photoemission Spectroscopy
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Kyle Shen, Cornell University
Abstract: Our ability to control electronic properties at semiconductor interfaces has had enormous scientific and technological implications. Extending this idea beyond the familiar semiconductors, one can now construct thin films of artificial "quantum" materials with atomic layer precision. With these new systems lies the promise of taking advantage of their strong quantum many-body interactions at interfaces or with dimensionality to control their electronic and magnetic properties. This is a new frontier in condensed matter physics, but to fully understand what happens in these artificial quantum materials, one requires advanced tools for both spectroscopy and synthesis. To achieve this, we have developed a new approach which combines oxide molecular beam epitaxy (MBE) with high-resolution angle-resolved photoemission spectroscopy (ARPES). As one example, I will describe our work on digital manganite superlattices ([LaMnO3]2n / [SrMnO3]n), comprised of alternating LaMnO3 and SrMnO3 blocks. Our ARPES measurements reveal that by controlling the separation between the LaMnO3-SrMnO3 interfaces, we can drive the interfacial quasiparticle states from 3D ferromagnetic metal, to a 2D polaron liquid, and finally to a pseudogapped ferromagnetic insulator. I will also describe some of our work on thin films of the elusive "infinite layer" cuprate Sr1-xLaxCuO2, which we can stabilize epitaxially, thus allowing us to address fundamental issues regarding the asymmetry between doping electrons and holes in the high-Tc cuprates.
Host: Rzchowski
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Friday, May 11th, 2012

Last Day of Class - No Colloquium

Dissertation Defense
Observation of Electron Antineutrino Disappearance at the Daya Bay Experiment
Time: 8:30 am
Place: 4274 Chamberlin Hall
Speaker: Bryce Littlejohn, UW Department of Physics Graduate Student
Abstract: Many experiments in the last few decades have demonstrated the neutrino's ability to change flavor while traveling through space and time, or oscillate. One of the last remaining unknown parameters describing this oscillation, theta13, is crucial in defining the magnitude of CP-violation in the lepton sector and examining the neutrino's role in the universe's matter-antimatter asymmetry. The Daya Bay experiment has measured theta13 with unprecedented precision by observing disappearance of reactor antineutrinos with identical detectors at multiple reactor distances. With roughly two months of data, the experiment has measured the value of sin^2(2theta13) to be 0.092 +- 0.017, and excluded the theta13=0 hypothesis to five standard deviations. This talk will describe the Daya Bay experiment, present an independent analysis of first Daya Bay data, and discuss the implications of this exciting measurement.
Host: Heeger
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Theory Seminar (High Energy/Cosmology)
Structure of dimension-six derivative interactions in pseudo Nambu-Goldstone N Higgs doublet models
Time: 1:00 pm
Place: 5280 Chamberlin Hall
Speaker: Yasuhiro Yamamoto, University of Tokyo
Abstract: We derive the general structure of dimension-six derivative interactions in the N Higgs doublet models, where Higgs fields arise as pseudo Nambu-Goldstone modes of a strongly interacting sector. We show that there are several relations among the dimension-six operators, and therefore the number of independent operators decreases compared with models on which only SU(2)_L x U(1)_Y invariance is imposed. As an explicit example, we derive scattering amplitudes of longitudinal gauge bosons and Higgs bosons at high energy on models involving two Higgs doublets, and compare them with the amplitudes in the case of one Higgs doublet.
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"This Week at Physics" poster: http://www.physics.wisc.edu/twap/posters/2012/2012-05-07.pdf

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