Events at Physics |
Events During the Week of October 10th through October 17th, 2010
Monday, October 11th, 2010
- No events scheduled
Tuesday, October 12th, 2010
- Chaos & Complex Systems Seminar
- "Climate, Energy, and the Economy: A new Theory of Everything".
- Time: 12:05 pm
- Place: 4274 Chamberlin Hall
- Speaker: Jim Pawley, UW-Madison Dept of Zoology
Wednesday, October 13th, 2010
- Special Wednesday Astronomy Talk
- The Hobby-Eberly Telescope Dark Energy Experiment
- Time: 12:00 pm - 1:00 pm
- Place: 4421 Sterling Hall
- Speaker: Gary Hill, University of Texas
- Abstract: The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) aims to make a direct detection of dark energy at z~3, in the case that it is a cosmological constant. HETDEX uses baryonic acoustic oscillations and the shape of the Lyman-alpha emitting (LAE) galaxy power spectrum to constrain H(z) and Da(z) to percent levels. As a result, the experiment will place tight constraints on possible dark energy evolution, complementing studies of the phenomenon at low redshift. HETDEX will also provide the most accurate constraint on the curvature of the Universe.<br>
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HETDEX will outfit the 10 m HET with a new wide field and an array of at least 150 integral-field spectrographs to survey a 400 sq. degree area in the north galactic cap. Each fiber-coupled unit spectrograph will cover 350-550 nm, simultaneously at 6 A resolution, providing ~36,000 spectra per exposure. This instrument, called VIRUS, will open up surveys of the emission-line universe for the first time, and in particular will be used to detect ~0.8 million LAE galaxies with 1.9 < z < 3.5 and more than a million [OII] emitting galaxies with z < 0.5. The 3-D map of LAE galaxies in 9 cubic Gpc volume will be used to constrain the expansion history at this early epoch.<br>
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The prototype of the VIRUS unit spectrograph (VIRUS-P) is a powerful instrument in its own right. Used on the McDonald 2.7 m Smith reflector, it covers the largest area of any integral field spectrograph, and has coverage down to 340 nm. It is currently in use for a pilot survey to better measure the properties of LAE galaxies in support of HETDEX, among other investigations where it is uniquely powerful.<br>
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I will describe the motivations for HETDEX and preliminary results from the Pilot Survey and look forward to completion of VIRUS on the upgraded HET as a unique facility in Astronomy <br>
- Host: Marsha Wolf
Thursday, October 14th, 2010
- R. G. Herb Condensed Matter Seminar
- Quantum Fluids in Random Media: Effects of Disorder on the Phases of <sup>3</sup>He
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: James A. Sauls, Northwestern University
- Abstract: The light isotope of Helium - 3He - is the purest phase of matter in nature. Zero-point fluctuations drive any impurity out of the bulk liquid. However, helium can be impregnated into porous glass. Silica aerogel is a solid formed from a network of strands and clusters of SiO2 that is almost entirely empty space. The system of quantum liquid infused into silica aerogel provides an novel system for studying the effects of disorder on the relative stability of ordered phases near a quantum critical point. I will describe some of the key experiments, and related theoretical interpretations, that have been carried which elucidate the role of disorder on the properties of both normal and superfluid 3He. These studies may also provide deeper insight into porous media with complex structure. The gossamer structure of silica aerogel is a realization of a random fractal - a solid with no long-range order, but power-law scaling of the density correlation function. I will also discuss possibilities for observing the effects of fractal correlations in the disordered medium on the properties of liquid 3He.
- Host: Maxim Vavilov
Friday, October 15th, 2010
- Theory/Phenomenology Seminar
- Automation of the Matrix Element Reweighting Method
- Time: 2:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Pierre Artoisenet, Ohio State University
- Abstract: Matrix element reweighting is a powerful experimental technique widely employed to maximize the amount of information that can be extracted from a collider data set. Given a set of theoretical hypotheses and a sample of experimental events, the method assigns a weight to each hypothesis on an event-by-event basis and in this way provides a discriminator between different theoretical assumptions. The computation of the weights is intricate, because it involves a difficult convolution of the theoretical information on the hard scattering with the experimentally available information on the final state. In this talk, I will present a general algorithm aimed at evaluating the weights appearing in the matrix element method for any process of interest in the standard model and beyond. The implementation builds on MadGraph, and is completely automated. I will also discuss a few sample applications that show the capabilities of the code and illustrate the possibilities for new studies that such an approach opens up. (The talk is based on work presented in arxiv:1007.3300.)
- Host: Neil Christensen
- Physics Department Colloquium
- Our Changing View of the TeV Sky
- Time: 4:00 pm
- Place: 2241 Chamberlin Hall (coffee at 3:30 pm)
- Speaker: Jordan Goodman, University of Maryland
- Abstract: The advent of ground-based atmospheric and water Cherenkov gamma-ray detectors, as well as, the Compton and Fermi satellites has revolutionized our view of the TeV sky. Twenty years ago there was only one known TeV gamma-ray source, the Crab. Today there are well over 100 detected sources - steady and variable, point-like and diffuse. We have also made great strides studying Gamma Ray Bursts, the most energetic processes in the Universe. Most recently, we have even discovered that charged TeV cosmic rays have unexpected anisotropies in their arrival directions suggesting the existence of local cosmic ray sources. The next generation detectors, CTA, HAWC and, IceCube will undoubtedly give us a better understanding of these exciting phenomena and almost certainly reveal more surprises. In this talk, I will review some of these results and show results from the Milagro gamma ray observatory. In addition I describe our next generation HAWC observatory currently under construction at high-altitude in Mexico.
- Host: Westerhoff