Events During the Week of
November 1st through November 7th, 2009

Monday, November 2nd, 2009

No events scheduled

Tuesday, November 3rd, 2009

Chaos & Complex Systems Seminar

Poetry, mathematics, and science

Time: 12:05 pm

Place: 5310 Chamberlin (Refreshments will be served)

Speaker: Robin Chapman, UW Department of Communicative Disorders

Abstract: I'll read poems of my own from Chaos seminar topics and from several recent anthologies that focus on the use of mathematics and science in poetry across the centuries, and then discuss briefly, and speculatively, what questions a science of poetry comprehension might ask.

Astronomy Colloquium

Can Quasars Quench Star Formation?

Time: 3:45 pm

Place: 3425 Sterling Hall

Speaker: Christy Tremonti, UW Astronomy Dept

Abstract: Since quasars were first recognized as cosmological sources their relation to galaxies has been a puzzle. We now know that quasars are powered by accretion of gas onto supermassive black holes at the centers of massive galaxies. What continues to elude our understanding is the impact that quasars have on their host galaxies. Recent numerical simulations suggest that quasars can drive powerful gas outflows that ultimately bring about an end to star formation and black hole activity. I will discuss observations designed to directly test this hypothesis. Because gas outflows are challenging to observe in the presence of a bright quasar, our study focuses on a sample of galaxies that are a few 100 million years past the peak of their star formation and black hole activity. In these 'post-starburst' galaxies we find evidence for outflowing cool gas with velocities upwards of 1000 km/s. We consider the energetics of the gas and argue that quasars play a significant role in removing gas from galaxies and quenching star formation.

String Theory Seminar

Toward a Holographic Model of Color Flavor Locking

Time: 4:00 pm

Place: 2301 Sterling Hall

Speaker: Heng-Yu Chen, UW-Madison

Host: Gary Shiu

Wednesday, November 4th, 2009

No events scheduled

Thursday, November 5th, 2009

R. G. Herb Condensed Matter Seminar

Invariant form of spin-transfer switching condition

Time: 10:00 am

Place: 5310 Chamberlin

Speaker: Yaroslaw Bazaliy, University of South Carolina

Abstract: Spin-transfer torque is a result of a non-equilibrium magnetic interaction induced by a flow of electric current. In nano-size devices spin transfer is a mechanism for current-induced magnetic switching, an effect with many applications in computer memory and logic. Calculations of critical switching currents were performed analytically and numerically for many systems. However, a clear physical interpretation of the results was available only in special cases. We firstly derive an invariant form of the current-induced switching condition and show that there exists a figure of merit for the current ability to destabilize a minimum of magnetic energy and induce switching. The resulting approach based on the "switching ability" of the current provides an intuitive physical picture of the switching behavior in devices of any geometry. We secondly consider the problem of current-induced stabilization of the saddle points and show that it happens via a different mechanism due to the topological restrictions. Saddle points are normally stabilized by a current-induced merger with other equilibria. Finally, we present and emerging full picture of possible switching scenarios in spin torque devices.

Host: Natalia Perkins

NPAC (Nuclear/Particle/Astro/Cosmo) Forum

The Baryon Resonance Spectrum and the 1/Nc Expansion

Time: 4:00 pm

Place: 5310 Chamberlin

Speaker: Richard Lebed, Arizona State University

Abstract: Why do baryon resonance multiplets exist, and what controls their formation and decays? It is natural to consider them as merely excited states of some three-quark or meson-nucleon potential. But these are just simplistic quantum-mechanical pictures that recognize neither the full field-theoretical complexities of QCD nor the extremely brief lifetimes of resonances due to quark pair production. Both of these issues are addressed by the 1/Nc expansion of QCD, where Nc is the number of color charges. Constraints arising at large Nc on meson-baryon scattering amplitudes not only create linear relationships between them, thus linking distinct partial waves and their embedded resonances, but also restrict the possible resonant decay channels. I present strong experimental evidence in favor of this approach, describe the multiplet structure that it predicts, and show how to perform the analysis beyond the strict large Nc limit by incorporating 1/Nc-suppressed effects. This program has been developed to the point that now one possesses a full effective field theory formalism for physics in the baryon resonance region.

Host: Michael Ramsey-Musolf

Introductory Graduate Seminar

Astrophysics II: Astroparticle Physics and Neutrinos

Time: 5:30 pm

Place: 2223 Chamberlin Hall

Speaker: Faculty, University of Wisconsin Department of Physics

Abstract: Balantekin, Barger, Chung, Halzen, Heeger, Karle, McCammon, Montaruli, Ogelman, Ramsey-Musolf, Timbie, Westerhoff, Zweibel

Friday, November 6th, 2009

Theory/Phenomenology Seminar

Rapidity Gap Events in Squark Pair Production at the LHC

Time: 2:30 pm

Place: 2301 Sterling Hall

Speaker: Sascha Bornhauser, University of New Mexico

Host: V. Barger

Physics Department Colloquium

Precision Muon Physics: Capturing a Moment in a Lifetime

Time: 4:00 pm

Place: 2241 Chamberlin Hall (coffee at 3:30 pm)

Speaker: David Hertzog, University of Illinois at Urbana-Champaign

Abstract: Low-energy, precision measurements are important to establish the parameters of the Standard Model and to test various predictions in the quest for new physics signatures. I will discuss two of our experiments that recently reported first physics results. Both involve the muon lifetime, leading to the Fermi Constant at a new level of precision and the nucleon weak pseudoscalar coupling constant g_P, determined in an unambiguous manner for the first time. Future plans include a Fermilab-based next-generation muon anomalous magnetic moment measurement, which follows on the our effort that has provided one of the strongest hints of physics beyond the Standard Model today.

Host: Heeger

Poster: http://www.physics.wisc.edu/twap/posters/2009/1514.pdf

"This Week at Physics" poster: http://www.physics.wisc.edu/twap/posters/2009/2009-11-02.pdf