ColloquiaAll colloquia are held in the Cunniff lecture hall, which is room 199 of the Science Center. Friday colloquia begin at 12:45 p.m. (unless otherwise noted). Pizza and drinks are served at 12:20 p.m. just outside the hall. There are also pre-colloquium talks for some of our visitors' colloquia. These are given by faculty members, usually a week before the actual colloquium, and are a good way for students (and others) to get background information to help them better understand the colloquium. For questions regarding the speakers and topics, please contact Prof. Catherine Crouch (ccrouch1 at swarthmore dot edu) at (610) 328-8386. Useful links
Time Keeping with Ultracold AtomsGretchen Campbell , JILA/University of ColoradoFri, Feb. 6, 2009, 12:45 PM Precise timekeeping is important for a number of everyday applications. Precise clocks are used for synchronizing telecom networks and GPS. They are also essential for navigation and for communicating with deep-space probes and rovers. It is predicted that with even higher precision, clocks will lead to new types of gravity sensors, and will allow for the testing of fundamental physical laws. Currently, the most precise clocks are made with cesium atoms, where microwave radiation is used to probe and measure an atomic resonance. At JILA, we’ve developed a new atomic clock which uses optical light to probe ultra-cold strontium atoms. By using higher frequency optical light instead of microwaves, the clocks divide time into smaller units, offering record precision. In our clock, a few thousand atoms of strontium are held very tightly in an optical lattice. The lattice is formed by standing waves of intense laser light. By carefully controlling the environment and interactions between our atoms, we’ve been able surpass the accuracy of the best cesium clocks. The JILA strontium clock would neither gain nor lose a second in more than 200 million years Pre-colloquium talk by Frank Moscatelli on Friday, Jan. 30, 2009, 12:45 PM in Cunniff The DRIFT Dark Matter DetectorDaniel Snowden-Ifft, Department of Physics, Occidental CollegeFri., Feb. 27, 2009, 12:45 PM The Directional Recoil Identification From Tracks (DRIFT) is designed to detect the dark matter thought to make up 85% of the mass of the universe. Unlike other dark matter detectors its design allows it to conclusively determine the galactic origin of the dark matter events created within it. I will describe the detector, its capabilities and our recent efforts to detect dark matter in the Boulby salt mine in England. More information is available at Prof. Snowden-Ifft's website. The "Main Sequence" of Galaxy FormationSandra Faber ('66), Department of Astronomy and Astrophysics, University of California, Santa CruzFri., April 24, 2009, 12:45 PM Major surveys have now thoroughly sampled the galaxy population at redshifts below z~1.4. This talk will summarize broadly what has been learned about galaxy evolution over these epochs, focusing on results from DEEP2 and Sloan. The main conclusion is that galaxy evolution is highly correlated with stellar mass, which in turn is plausibly correlated with halo mass. A useful working model is that galaxy evolution is driven principally by halo mass and that the star formation rate is given uniquely by halo mass at each redshift over these epochs. More information is available at Prof. Faber's website.
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