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Events on Thursday, December 13th, 2012

R. G. Herb Condensed Matter Seminar
Field-induced thermal transport in BEC antiferromagnets
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Sasha Chernyshev, University of California, Irvine
Abstract: Recent experiments in BEC quantum magnets exhibit a dramatic evolution of the thermal conductivity of these materials in magnetic field. By considering various relaxation mechanisms of bosonic excitations in the vicinity of the BEC quantum-critical point at finite temperature we provide a detailed explanation of several unusual features of the data. We identify the leading impurity-scattering interaction and demonstrate that its renormalization due to quantum fluctuations of the paramagnetic state compensates the related mass renormalization effect. This explains the enigmatic absence of the asymmetry between the two critical points in the low-T thermal conductivity data, while such an asymmetry is prominent in many other physical quantities. The observed characteristic "migration'' of the peak in thermal conductivity away from the transition points as a function of temperature is explained as due to a competition between an increase in the number of heat carriers and an enhancement of their mutual scattering. An important role of the three-boson scattering processes within the ordered phase of these systems is also discussed. Other qualitative and quantitative features of the experiment are clarified and the future directions are sketched.
Host: Perkins
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Careers in Physics Monthly Meeting
Grad School
Time: 3:00 pm
Place: Chamberlin 5310
Speaker: Physics grad students, UW-Madison
Abstract: At this next informal meeting of "Careers in Physics", we will address the various questions lingering in undergraduate physics students' minds as the time comes to think about graduate school or to apply. Most undergraduate students wonder about the peculiarities of the work associated with each physics field in addition to what graduate school is like in general. To help answer these questions and others, we have assembled a panel of graduate students from our own department who have kindly volunteered their time.
Host: Reina Maruyama
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Astronomy Colloquium
The WISP survey: overview of recent results for galaxies in the 1<z<2 redshift range
Time: 3:30 pm - 5:00 pm
Place: 4421 Sterling Hall
Speaker: Claudia Scarlata, CALTECH
Abstract: The WFC3 Infrared Spectroscopic Parallel Survey (WISP) is a large ( 750 orbits) HST program using WFC3 slitless IR spectroscopy to detect thousands of galaxies across a wide redshift range 0.3 &lt; z &lt; 2.3. I will present an overview of recent results on emission line galaxies, including a statistical determination of their dust extinction properties and the discovery of a new population of extremely strong emission-line dwarf galaxies. I will also discuss the stellar population properties of passive galaxies at za^1/41.5 derived from the combination of the WISP IR spectra and broad-band HST optical and Spitzer photometry.
Host: Prof Amy Barger
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