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Events at Physics

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Events During the Week of December 5th through December 12th, 2010

Monday, December 6th, 2010

Plasma Physics (Physics/ECE/NE 922) Seminar
"Liquid Metal Plasma-Facing Components and the Lithium Tokamak eXperiment (LTX)"
Time: 12:00 pm
Place: 2535 Engineering Hall
Speaker: Dick Majeski, Princeton Plasma Physics Laboratory
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Plasma Theory Seminar
"Flux Surface Shaping and Ballooning Stability for Tokamaks with 3-D RMP Fields"
Time: 4:00 pm
Place: 514 ERB
Speaker: Tom Bird, UW-Madison Dept of Engineering Physics
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Tuesday, December 7th, 2010

Atomic Physics Seminar
Measurement of the dipole moment for transitions to Rydberg states in ultracold rubidium
Time: 11:00 am
Place: 5280 Chamberlin
Speaker: Michal Piotrowicz, The Open University, Milton Keynes UK
Abstract: Dipole matrix elements are required for calculations of numerous spectroscopic properties of excited atoms including oscillator strengths, polarisabilities and radiative lifetimes. There is no exact analytical solution for the calculation of radial matrix elements for alkali atoms, however many theoretical models have been developed that include numeric integration of Schroedinger's equation in the Coulomb approximation with quantum defects taken as input parameters or using various model potentials. In quasiclassical methods the radial matrix elements are calculated avoiding the direct numerical integration using transcendental functions. Despite the large number of existing theoretical models, lack of experimental data on dipole matrix elements for rubidium complicates their verification.

In my talk I will present the experimental setup built at The Open University, UK to investigate the ultracold Rydberg atoms. I will show our first results of the measurements of the dipole moments for the transitions to the Rydberg states by investigation of the electromagnetically induced transparency (EIT) in ultracold 87Rb gas. The absorption profile of a weak probe laser beam on 5S1/2 → 5P3/2 transition is observed in the presence of a strong coupling laser beam at 480 nm driving the 5P3/2nD5/2 transition for the Rydberg states with principal quantum numbers in the range 20≤n≤48. The strong dependence of the shape of the EIT spectrum on the Rabi frequency of the transition between the first excited state and Rydberg states allowed us to directly measure the dipole moments of the transitions involved for several values of principal number n.

The dipole matrix elements for transitions measured in our experiment are compared with theoretical methods including quasiclassical calculations based on Dyachkov-Pankratov model, and Coulomb approximations. A very good agreement with the theoretical calculations is observed.

I will conclude the talk with the outline of further projects with ultracold Rydberg atoms that are carried out at the Open University.
Host: Mark Saffman
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String Theory Seminar
Title to be announced
Time: 4:00 pm
Place: 5280 Chamberlin Hall
Speaker: Fernando Marchesano, IFT Madrid
Host: Shiu
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Wednesday, December 8th, 2010

NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Pierre Auger Neutrino Measurement
Time: 2:00 pm
Place: 4274 Chamberlin
Speaker: Lukas Nellen, UNAM
Abstract: The Pierre Auger Observatory is currently the world's largest cosmic ray
observatory. The southern site, in Malarguee, Mendoza, Argentia, covers
3000 km^2, instrumented with more than 1600 water Cherenkov detectors and
24 fluorescence telescopes.

I will present the status of the Pierre Auger Observatory and its recent
results. Even though the obesravtory was designed primarily as a detector
for charged cosmic rays, was clear from the beginning that it can also
identify photons and neutrinos. I will discuss the methods for the
identification of the primary cosmic rays, with emphasis on neutrino
tagging, and present the flux limits obtained.
Host: Teresa Montaruli
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Special IceCube Seminar
Antineutrino Oscillation Results from MiniBooNE & Implications for IceCube & Future Experiments
Time: 4:00 pm
Place: 5280 Chamberlin Hall
Speaker: Bill Louis, Los Alamos National Laboratory
Host: Francis Halzen
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Thursday, December 9th, 2010

R. G. Herb Condensed Matter Seminar
Theory of Josephson photomultipliers: current biased Josephson junctions as microwave photon counters
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Emily Pritchett, Institute for Quantum Computing, University of Waterloo
Abstract: Superconducting devices have enabled many experimental demonstrations of on-chip quantum optics in the microwave regime. While microwave fields are usually detected by linear amplification, detection of single low-energy microwave photons remains a challenge to experimental reproduction of quantum optical effects that require photon counting. We analyze the use of single current biased Josephson junctions as Josephson photomultipliers (JPMs) for microwave photon counting. By analyzing the backaction of a switching event in the junction, we show that JPMs are close to binary detectors responding only to the presence or absence of resonant photons. We discuss applications of a microwave photon counter, including on-chip demonstration of the Hanbury-Brown Twiss effect and efficient state tomography.
Host: Robert McDermott
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Astronomy Colloquium
Gas Accretion in Galaxies
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Dusan Keres, Harvard Smithsonian Center for Astrophysics
Abstract: &quot;Most galaxies are actively star forming at all epochs. However, observations of dense, galactic gas indicate that, at any epoch, there is not enough gas in galaxies to support evolution of star formation activity over time. This suggests that galactic gas is being replenished from the intergalactic medium.<br>
<br>
I use fully cosmological simulations of galaxy formation to study the gas supply into galactic component from high redshift to present. At high redshift &quot;smooth&quot; infall of cold filamentary gas dominates the gas supply of all galaxies. This &quot;cold mode accretion&quot; is unlike the accretion in the standard model of galaxy formation in which cooling of the hot halo atmospheres is a source of gas supply to galaxies. Cold mode accretion is a major driver of very active star formation of high-z galaxies enabling such activity to proceed for a significant fraction of the Hubble time. Gas accretion rates at a given halo and galaxy mass decrease with time, causing the drop in star formation rates. At low redshift hot virialized gas can cool in some of the halos, but cold gaseous clouds that form from infalling filaments can dominate gas supply in galaxies such as Milky Way.<br>
<br>
In this talk I will describe properties, physics and consequences of cold gas accretion from the intergalactic medium as well as predictions for the observational probes of cold halo gas that can provide strong constraints on the models. I will also discuss remaining open questions and future directions in the studies of galactic gas accretion, including new computational methods and observations with upcoming facilities.&quot;<br>
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Friday, December 10th, 2010

Theory/Phenomenology Seminar
Signatures of WIMPless Dark Matter
Time: 12:00 pm
Place: 5280 Chamberlin Hall
Speaker: Jason Kumar, University of Hawaii at Manoa
Host: Lisa Everett
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Physics Department Colloquium
Holiday Colloquium
Time: 4:00 pm
Place: 2241 Chamberlin Hall
Speaker: Holliday Colloquium
Abstract: Hold the Date
Host: Grad Students
Poster: https://www.physics.wisc.edu/events/posters/2010/1868.pdf
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