Events at Physics |
Events During the Week of September 13th through September 20th, 2009
Monday, September 14th, 2009
- Plasma Theory Seminar
- Background and Recent Progress on Simulation of Giant Sawteeth in Tokamaks with NIMROD
- Time: 4:00 pm
- Place: 514 ERB
- Speaker: Dalton Schnack, UW-Madison, Dept of Physics/Plasma
Tuesday, September 15th, 2009
- Chaos & Complex Systems Seminar
- Long-term cortical and subcortical neuromodulation induced by electrical tongue stimulation
- Time: 12:05 pm
- Place: 4274 Chamberlin (Refreshments will be served)
- Speaker: Joe Wildenberg, UW Department of Neuroscience
- Abstract: The use of electrical neurostimulation to treat neurological disorders is expanding from initial applications in epilepsy and Parkinson's disease to conditions such as depression, obsessive-compulsive disorder, balance disorders, and as an adjuvant to behavioral therapy during neurorehabilitation for stroke. Our group has developed a non-invasive technique that stimulates the central nervous system through the tongue. Previous work has shown this technique efficacious as therapy for balance disorders with beneficial effects lasting weeks to months after the stimulation therapy has ended. Here I will present a functional magnetic resonance imaging study indicating that stimulation of the cranial nerves via afferents in the tongue can influence neural structures within the balance-processing network to produce positive behavioral effects. Furthermore, the results of this study indicate that this stimulation can modify neural processing of tasks not encountered during the stimulation sessions. This seems to be the first evidence of long-term network-wide processing plasticity induced by electrical neurostimulation in humans.
- Astronomy Colloquium
- "Using Numerical Simulations to Study the Formation and Evolution of Galaxies
- Time: 3:30 pm
- Place: 3425 Sterling Hall
- Speaker: Dr. T.J. Cox, Harvard Smithsonian Center for Astrophysics
- Abstract: The past decade has produced an amazingly robust picture for the universe we live in. This picture predicts that structure forms hierarchically, i.e., small objects collapse at early times and grow via mergers and gravity. The prevailing idea for the formation of galaxies is that the morphology and structure that we observe is a direct byproduct of this hierarchical merger history; however, a detailed mapping between specific merger histories, and the wide variety of galaxy types, is still uncertain. By using a comprehensive set of state-of-the-art numerical simulations, we show how this process is being studied, and what some of the common scenarios might be. For example, we show that a single disk-disk merger, such as that which will occur in 5 Gyr between our own Milky Way and our nearest neighbor Andromeda, is a plausible mechanism to form many elliptical galaxies provided that dissipation is involved. We also show were this picture fails, and outline how current and future work will address these shortcomings and yield testable predictions of the model.
- Host: Prof Christi Tremonti
Wednesday, September 16th, 2009
- No events scheduled
Thursday, September 17th, 2009
- R. G. Herb Condensed Matter Seminar
- Optimal quantum gates in imperfect qubits
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Frank Wilhelm, University of Waterloo & ICQ
- Abstract: Physical qubits are necessarily not perfect: they typically contain higher levels beyond the two-state Hilbert space of a qubit and couple to decoherence mechanisms. We show how optimal control theory helps to accommodate these imperfections and still realize fast high-fidelity quantum gates. For the case of a weakly anharmonic multilevel system containing a qubit, we introduce the derivative removal by adiabatic gate (DRAG) technique that retains adiabaticity even for fast gates. This technique allows improvement of gate fidelity in realistic superconducting setups by an order of magnitude beyond the present state of the art and to get close to the fault-tolerance threshold [1] and beyond, if multiple carrier frequencies are used. In the case of non-Markovian decoherence, optimal gates are extremely short Rabi bursts at the optimum working point, which are modulated to refocus counter-rotating terms [2].
[1] F. Motzoi, J. M. Gambetta, P. Rebentrost, and F. K. Wilhelm, Phys. Rev. Lett., in press, arXiv:0901.0534.
[2] P. Rebentrost, I. Serban, T. Schulte-Herbrueggen, and F. K. Wilhelm, Phys. Rev. Lett. 102, 090401 (2009). - Host: Robert McDermott
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- TeV Gamma-Ray Astronomy with Milagro and HAWC
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Andrew Smith, University of Maryland, College Park
- Abstract: Milagro was a water Cherenkov detector that continuously viewed<br>
the entire overhead sky. The large field-of-view combined with<br>
the long observation time makes Milagro the most sensitive<br>
instrument available for surveys and especially for the study<br>
of large, low surface brightness sources. In this talk I will<br>
present recent results from Milagro including the identification<br>
of several new TeV sources associated with Fermi BSL (bright<br>
source list) objects within the Galactic plane. The success of<br>
Milagro has lead to the proposed High Altitude Water Cherenkov<br>
(HAWC) Observatory. HAWC will be built at a high altitude site<br>
(4100m a.s.l.) in central Mexico. The increased elevation, along<br>
with the re-optimization of the design will lead to a 15x<br>
sensitivity improvement compared to Milagro. - Host: Stefan Westerhoff
- Introductory Graduate Seminar
- High Energy Experimental
- Time: 5:30 pm
- Place: 2223 Chamberlin Hall
- Speaker: Carlsmith, Dasu, Heeger, Herndon, Mellado, Pan, Pondrom, Smith, Wu, University of Wisconsin Department of Physics
Friday, September 18th, 2009
- Physics Department Colloquium
- Mack Lecture
- On the Verge of Umdeutung in Minnesota: John H. Van Vleck and the Transition from the Old Quantum Theory to Matrix Mechanics
- Time: 4:00 pm
- Place: 2241 Chamberlin Hall (coffee at 3:30 pm)
- Speaker: Michel Janssen, University of Minnesota
- Abstract: In October 1924, The Physical Review, a relatively minor journal at the time, published a remarkable two-part paper by John H. Van Vleck, working in virtual isolation at the University of Minnesota. Using Bohr's correspondence principle and Einstein's quantum theory of radiation along with advanced techniques from classical mechanics, Van Vleck showed that quantum formulae for emission, absorption, and dispersion of radiation merge with their classical counterparts in the limit of high quantum numbers. The paper is similar in many ways to the paper on dispersion theory by Kramers and Heisenberg a few months later that led directly to the famous Umdeutung (reinterpretation) paper of July 1925 with which Heisenberg laid the foundations for matrix mechanics. This makes Van Vleck's paper extremely valuable for the reconstruction of the genesis of matrix mechanics. It also makes it tempting to ask why Van Vleck did not take the next step and develop matrix mechanics himself.
- Host: Lin & Huber