Theory Center Seminar Series
Subject:  Rho and Sigma Mesons From Chiral and Large Nc Dynamics 
Speaker:  Enrique Ruiz Arriola, University of Granada 
Date:  Monday, April 18, 2011 
Time:  10:00 a.m. 
Place:  CEBAF Center, Room F113 
Abstract:  The large Nc and chiral expansions have been used to
examine the properties and nature of resonances in
pipi scattering. I review some important aspects of
this problem from different viewpoints.
References:

Subject:  PiN Scattering and Pion Photoproduction in a Dynamical CoupledChannels Model 
Speaker:  Fei Huang, University of Georgia 
Date:  Monday, April 25, 2011 
Time:  1:00 p.m. (coffee at 12:45 p.m.) 
Place:  CEBAF Center, Room L104 
Abstract:  The dynamical coupledchannels model developed by the JuelichGeorgia group is presented, which presently includes the gammaN, piN, etaN and SigmaK stable channels as well as the effective pipiN channels piDelta, rhoN and sigmaN. Recent progress on the description of piN > SigmaK and pion photoproduction within this model is discussed, with the emphasis given on the gauge invariance of the photoproduction amplitudes. 
Subject:  The Imbalanced Fermi Gas at Unitarity 
Speaker:  Olga Goulko, Cambridge, UK 
Date:  Monday, May 2, 2011 
Time:  1:00 p.m. (coffee at 12:45 p.m.) 
Place:  CEBAF Center, Room L104 
Abstract:  Lattice field theory is a useful tool for studying strongly interacting theories in condensed matter physics. A prominent example is the unitary Fermi gas: a twocomponent system of fermions interacting with divergent scattering length. With Monte Carlo methods this system can be studied from first principles. In the presence of an imbalance (unequal number of particles in the two components) a sign problem arises, which makes conventional algorithms inapplicable. I will show how to apply reweighting techniques to generalize the recently developed worm algorithm to the imbalanced case, and present results for the critical temperature and other thermodynamic observables at the critical point, namely the chemical potential, the energy per particle and the contact density. I will also present some preliminary results for these observables at temperatures beyond the critical point. 