Events at Physics |
Events on Thursday, September 24th, 2009
- R. G. Herb Condensed Matter Seminar
- Biot-Savart correlations in layered superconductors
- Time: 10:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Kumar Raman, University of California - Riverside
- Abstract: We discuss the superconductor to normal phase transition in an infinite-layered type-II superconductor in the limit where the Josephson coupling between layers is negligible. We model each layer as a neutral gas of thermally excited pancake vortices. We assume the dominant interaction between vortices in the same and in different layers is the electromagnetic interaction between the screening currents induced by these vortices. Our main result, obtained by exactly solving the leading order renormalization group flow, is that the phase transition in this model is a Kosterlitz-Thouless transition despite being a three-dimensional system. While the transition itself is driven by the unbinding of two-dimensional pancake vortices, an RG analysis of the low temperature phase and a mean-field theory of the high temperature phase reveal that both phases possess three-dimensional correlations. An experimental consequence of this is that the jump in the measured in-plane superfluid stiffness, which is a universal quantity in 2d Kosterlitz-Thouless theory, will receive a small non--universal correction (of order 1% in Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$). This overall picture places some claims expressed in the literature on a more secure analytical footing and also resolves some conflicting views.
Reference: Phys. Rev. B 79, 174528 (2009), arXiv:0902.1547 - Host: Natalia Perkins
- Special Interest Presentation
- Intersections Between Physics and the Movement Arts
- Time: 10:30 am
- Place: Grainger Hall Plenary Room
- Speaker: Elizabeth Streb, MacArthur Genius Award winner and world-renowned choreographer
- Abstract: Elizabeth Streb is a MacArthur "Genius" Award winner and world-renowned choreographer and has been celebrated as the "Evel Knievel of dance" for her muscular, daredevil approach to movement. Streb holds an honorary doctorate from Rhode Island College and a master of arts in time and space from New York University's Draper Program. Streb's choreography, which she calls "PopAction," intertwines the disciplines of dance, athletics, boxing, rodeo, the circus and Hollywood stunt-work. The result is a bristling, muscle-and-motion vocabulary that combines daring with strict precision in pursuit of the public display of "pure movement". Come to this special presentation for Physics students and faculty, where Streb will discuss the intersections between physics and the movement arts.
Elizabeth Steb, Founder/Action Architect, Streb Lab for Action Mechanics (SLAM), Brooklyn, New York www.streb.org
(Enter Grainger Hall at Park and University-into the new addition of Grainger Hall-and the Plenary room will be directly to your right).
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Special Colloquium
- Time-lapse seismic monitoring of reservoir deformation
- Time: 4:00 pm
- Place: 2103 Chamberlin (tentative) (coffee & cookies at 3:30)
- Speaker: Paul Hatchell, Shell International E&P, Research and Development, Houston, TX
- Abstract: Seismic imaging is a technology used worldwide by the oil industry to look into the subsurface and determine underground structures and their potential for oil and gas production. Time-lapse seismic monitoring is a relatively new technology that consists of carefully repeating a seismic image months to years after production starts and looking for changes that indicate where production did or did not occur to help guide future operations. <br>
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Production of oil and gas is often accompanied by a large reduction in the reservoir fluid pressure that in some cases leads to compaction as large as several meters. The deformation of the reservoir layers is coupled to the adjacent rocks and leads to changes in the stress and strain fields that extend a great distance away from the reservoir. Time-lapse seismic measurements through these rocks show large variations that are useful for monitoring the distribution of deformation within the reservoir.<br>
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The compaction induces seismic velocity changes that are observed on many different wave types including conventional P-P reflection seismic, P-S mode converted seismic, and surface waves such as the Scholte wave and refracted compressional waves. Using geomechanical models that predict changes in stress and strain fields within the earth we can start to understand the factors that control the changes in seismic velocities. We find that simple non-linear relationships between velocity and strain produce forward models that match many of our observations. <br>
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- Host: Balantekin
- Introductory Graduate Seminar
- Plasma
- Time: 5:30 pm
- Place: 2223 Chamberlin Hall
- Speaker: Boldyrev, Forest, Sarff, Schnack, Terry, Zweibel, University of Wisconsin Department of Physics