# Physics & Astronomy Colloquium
3:30 PM, Friday, September 7, 2012
Room 155, Chem-Phys Building
**Dr. Marcos Rigol**
Georgetown University
**Relaxation dynamics and thermalization in isolated quantum systems
**
Little more than fifty years ago, Fermi, Pasta, and Ulam set up a numerical
experiment to prove the ergodic hypothesis for a one-dimensional lattice of
harmonic oscillators when nonlinear couplings were added. Much to their
surprise, the system exhibited long-time periodic dynamics with no signals of
ergodic behavior. Those results motivated intense research, which ultimately
gave rise to the modern chaos theory and to a better understanding of the
basic principles of classical statistical mechanics. More recently,
experiments with ultracold gases in one-dimensional geometries have challenged
our understanding of the quantum domain. After bringing a nearly isolated
system out of equilibrium, no signals of relaxation to the expected thermal
equilibrium distribution were observed. Some of those results can be
understood in the framework of integrable quantum systems, but then it remains
the question of why thermalization did not occur even when the system was
supposed to be far from integrability. In the latter regime, thermalization is
expected to occur and can be understood on the basis of the eigenstate
thermalization hypothesis. In this talk, we discuss some of the early
theoretical and experimental results on this topic. We then show how
thermalization breaks down in finite one-dimensional quantum systems
as one approaches an integrable point. We establish a direct connection
between the presence or absence of thermalization and the validity or failure
of the eigenstate thermalization hypothesis, respectively.
Refreshments will be served in CP 179 at 3:15 PM |