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This Week at Physics

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Events on Thursday, December 5th, 2013

R. G. Herb Condensed Matter Seminar
Non-equilibirum Dynamics with Cold Polar Molecules: Glasses and the Hexatic Phase
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Dr. Wolfgang Lechner, University of Innsbruck
Abstract: The realization of cold ensembles of polar molecules has opened a new pathway to explore the dynamics of quantum many body systems with strong, long-range and anisotropic dipolar interactions. While theoretical studies have so far focused on the equilibrium phases in the highly degenerate quantum regime , I will focus in my talk on non-equilibirum dynamics in the regime where quantum and thermal fluctuations are of the same order of magnitude. I will present two proposals: i.) a study on the glass transition in the presence of quantum fluctuations and ii.) a study on quantum fluctuations in the hexatic phase. i.) I will show, how the glass phase can be prepared in a bilayer system of ultracold dipolar molecules and present results on classical and quantum glassy behavior, characterized by long tails in the relaxation time and dynamical heterogeneity. I will also present experimental accessible order parameters based on marker molecules, distinguished by properly chosen internal levels, and find quantum features of dynamical heterogeneity. ii.) The hexatic phase is an intermediate phase in two dimensional systems when going from the crystal to the liquid phase. I will present results on the influence of quantum fluctuations on the nature of the hexatic phase and methods that allow one to measure these effects in a setup with polar molecules.
Host: Chubukov, Saffman & Yavuz
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Astronomy Colloquium
“Star Formation, Solar Physics, and Stellar Astrophysics: A Data-Intensive Approach”
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Keivan Stassun, Vanderbuilt University
Abstract: Large time-domain surveys, from the ground and from space, are enabling new data-intensive approaches to a variety of problems in stellar and solar astrophysics. This talk describes four projects, each serving as a vignette of a different but complementary mode of data-intensive research into the<br>
formation and evolution of Sun-like stars. The SLoWPoKES project extracts from the Sloan Digital Sky Survey the largest sample of wide low-mass binaries ever assembled, which we use to constrain binary star formation theory and the role of third bodies in the formation of tight binaries. The EB Factory project seeks to identify rare, but astrophysically very interesting, case studies from among the large numbers of eclipsing binaries being harvested by surveys for transiting exoplanets. We use a set of rare low-mass and brown-dwarf eclipsing binaries to elucidate the role of magnetic activity in altering the basic properties of low-mass stars and brown dwarfs, affecting our understanding of the stellar initial mass function and the frequency of brown dwarfs in stellar populations. The X10000 Project studies the structures of young stellar coronae in order to understand the role of extreme coronal mass ejections in the angular momentum evolution of young stars. As a by-product of this work, we have determined the first robust empirical relationship between X-ray flare energy and coronal mass loss for the Sun. Finally, we use the Kepler database of precision light curves for 150,000 stars to present a new, a Eurooephotometric variability HR diagrama Euro which enables accurate determination of stellar surface gravities, improves our knowledge of exoplanet properties, and enhances our ability to identify the most radial-velocity quiet stars for exoplanet discovery.
Host: Prof Emeritus Ed Churchwell/Barb Whitney
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