Events at Physics |
Events During the Week of March 1st through March 8th, 2009
Monday, March 2nd, 2009
- Atomic Seminar
- High-Precision Single-Ion Penning Trap Mass Spectrometry
- Time: 4:00 pm
- Place: 5310 Chamberlin
- Speaker: Matthew Redshaw, Florida State University
- Abstract: The development of single-ion Penning trap techniques during the 1980s and the refinement of these techniques over the past two decades has enabled atomic mass comparisons with fractional precisions of ~0.1 - 0.01 parts-per-billion. During six years of operation, the Florida State University Penning trap has produced over 20 of the world's most precisely known atomic masses, and two measurements of dipole moments of molecular ions, with application to a wide range of fields including determination of fundamental constants, metrology, neutrino physics, nuclear physics, molecular spectroscopy and molecular structure.
In this talk I will describe the FSU Penning trap system and the unique techniques employed, including phase coherent cyclotron frequency measurement via image charge detection, and the implementation of a technique in which the two ions whose cyclotron frequencies are to be compared are simultaneous confined in the trap. - Host: Mark Saffman
- High Energy Seminar
- The Truth the Top Quark is Hiding
- Time: 4:00 pm - 5:00 pm
- Place: 4274 Chamberlin (Coffee and Cookies at 3:45 pm)
- Speaker: Andrew Ivanov, University of California Davis
- Host: Matt Herndon
Tuesday, March 3rd, 2009
- R. G. Herb Condensed Matter Seminar
- Radio Frequency Spectroscopy in Ultra-cold Fermi gases Undergoing BCS-BEC Crossover
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Yan He, University of Chicago
- Abstract: In recent years, ultra-cold atoms opened an exciting new direction of condensed matter physics. Radio frequency spectroscopy provides an important tool to understand energy gap and quasi-particle dispersion in ultra-cold Fermi gases. Here we present a systematic study of the RF spectra of Fermi gases in the BCS-BEC crossover. We discuss the effects of traps, population imbalance, final state interactions over the entire range of temperatures and compare theory with experiment. The result shows that this broad range of phenomena can be accommodated within the BCS-Leggett description of BCS-BEC crossover.
- Host: Mark Friesen
- Chaos & Complex Systems Seminar
- Place; It's complicated: Nagas in the Himalaya
- Time: 12:05 pm
- Place: 4274 Chamberlin
- Speaker: Chris Limburg, UW Department of Geography
- Abstract: Place is more complex than we think it is. Places--so often taken for granted--shape our environment, society, and imagination. This talk will elaborate the ways that we think about places. It will address questions like: what is a place, exactly? How does thinking about places help us understand our world? And: isn't place just a location in inert space? In answering these questions, I will argue for the importance of using place as a lens as well as a site. Examining place epistemologically and ontologically, this talk will demonstrate the usefulness of thinking geographically about our fragmented relationship with the environment. With a deeper sense of place we can engage environment, society, and self as emergent despite their seeming fixity. The talk will first outline the debates concerning the nature of place in geography. Then it will use the example of naga nature spirits in the Kathmandu valley to illustrate the complexity of place.
- String Theory Seminar
- An Inverted Mass Hierarchy for Exciting Dark Matter
- Time: 2:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Andrew Frey, McGill University
- Astronomy Colloquium
- The Origins and Evoluation of Weak MB II Quasar Absorption Line Systems
- Time: 3:30 pm
- Place: 6515 Sterling Hall
- Speaker: Anand Narayanan, UW Astronomy Dept
- Abstract: Among the various class of intervening quasar absorption line systems, the origin(s) of weak Mg II absorbers have remained a mystery. It is not well understood what kind of astrophysical structures produce these absorption systems. I will present results from UV and optical spectroscopic surveys of ~100 quasar sight lines, which has yielded a full census of this absorber population over a significant fraction of the history of the universe. Based on the results we extend the proposition that a substantial fraction of these absorbers could be tracing gas at the galaxy-IGM interface, analogous to Galactic high-velocity cloud structures.<br>
- Host: UW Madison
- String Theory Seminar
- A Tour of Flux Compactification Dynamic
- Time: 4:30 pm
- Place: 5280 Chmaberlin Hall
- Speaker: Andrew Frey McGill
Wednesday, March 4th, 2009
- No events scheduled
Thursday, March 5th, 2009
- R. G. Herb Condensed Matter Seminar
- Quantum computing with Ba ions
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Boris Blinov, University of Washington - Seattle
- Abstract: We are setting up to do basic quantum logic operations with trapped Ba ions at the University of Washington. I will describe our recent progress which includes: single qubit preparation, manipulation and detection; ultrafast pulsed laser excitation of single ions for ion-photon entanglement demonstration; a very high-N.A. optical system for efficient collection of single ion fluorescence; and coupling of such fluorescence into a single-mode optical fiber. Our future plans include entanglement of two Ba ions over long (~ 1 km) distance and the development of ultrafast quantum logic gates between small sets of ions.
- Host: Natalia Perkins
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Active Galactic Nuclei: Sources for ultra high energy cosmic rays?
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Peter L. Biermann, MPI Bonn
- Abstract: Particles near $10^{20}$ eV are the most energetic particles known to us in the universe, also called ultra high energy cosmic rays. Their observations have led us to build the largest detector systems in the world, in the South the Auger air-shower array, and in the North the Telescope Array, and perhaps soon Auger-North. With these and earlier arrays events have been detected of an energy up to $3 , 10^{20}$ eV, which is a macroscopic energy. There have been two predictions: one that due to interaction with the microwave background the spectrum should show a turnoff near $5 , 10^{19}$ eV; a turn-off has been confirmed by two experiments, HiRes and Auger. Second, that active galactic nuclei, possibly radio galaxies, should be the accelerators, based on the non-thermal optical spectra of knots and hot spots in radio galaxies; this is now tentatively confirmed by Auger, but contradicted by HiRes. I will go through some fundamental problems with the predictions, which teach us about active galactic nuclei and starburst galaxies. Apart from differentiating various remaining options, such as gamma ray bursts, how to generate these particles, and their source population, there is one major difficulty: the lack of understanding of the cosmological web of magnetic fields, which may influence the propagation of high energy particles; here it is especially important to understand the role of our local cosmic neighborhood and a possible galactic magnetic wind. It appears from MHD simulations that magnetic scattering leads to a steep distribution function of scattering angles of the deviation from a straight line path for the arriving particles, and also to a substantial delay time distribution. I will list and debate the merits of the closest candidate sources, Cen A, Vir A and For A. I will discuss the observational and theoretical limits for an exemplary set of models, the predictions like chemical abundances, that result from these models, and how present and future observations will test our conclusions, especially with the the Auger Array, the Telescope Array (TA), the neutrino observatory IceCube, the TeV Cherenkov $gamma$-ray telescopes, and the future space observatory EUSO. We face a number of exciting challenges for plasma physics, particle physics, cosmology, astronomy, and may attain better tools for our deep understanding of matter.
- Host: Stefan Westerhoff
Friday, March 6th, 2009
- Physics Department Colloquium
- Fay Ajzenberg-Selove Distinguished Lecture
- Harnessing Attosecond Science in the Quest for Coherent X-Rays
- Time: 4:00 pm
- Place: 2241 Chamberlin Hall (coffee and cookies at 3:30 pm)
- Speaker: Margaret Murnane, JILA/UC-Boulder
- Abstract: To generate coherent x-ray beams, extreme nonlinear optical techniques have succeeded in upshifting visible laser light into the soft x-ray region of the spectrum. This ability has given us a new coherent light source that spans a large spectral bandwidth, with pulse durations on sub-femtosecond or attosecond (1 as=10-18 s) time-scales. Equally intriguing is the fact that we have learned how to use light to coherently manipulate electrons in atoms and molecules on their fundamental, attosecond, timescales. The richness and complexity of attosecond science and technology is only just beginning to be uncovered. As I will discuss in this talk, attosecond science can capture the complex, interwoven dance of electrons in molecules and materials. Attosecond science also shows great promise for developing new ultrasensitive molecular imaging and spectroscopic techniques. Finally, attosecond science represents the most promising avenue to achieve what had seemed hopelessly impractical until now -- the generation of bright, coherent, hard x-ray beams using a tabletop-scale apparatus.
- Host: Everett and Yavuz