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Monday, July 20, 2009
3:00 PM - 4:00 PM
CNLS Conference Room (TA-3, Bldg 1690)


The unitary Fermi gas: so simple and yet so complex!

Aurel Bulgac
University of Washington

Ten years ago George Bertsch challenged the many-body community to figure out the basic properties of a system of spin 1/2 fermions interacting with a zero range potential and an infinite scattering length. As George Bertsch has intimated, this system has no other dimensional parameters except the average separation between particles, and thus its energy is, up to an undetermined dimensionless constant, proportional to the energy of a non-interacting Fermi gas, if stable. However, these particles interact with each other with essentially an infinite scattering cross section and it was clear ten years ago that this system, which in many respects is similar to dilute neutron matter which exists in neutron stars, is a highly nontrivial one. Since then many of the properties of this system have been unravelled, both theoretically and experimentally. It was firmly established so far, among many other things, that this system is stable and superfluid, with the highest critical temperature (in appropriate units) known. What perhaps emerged as perhaps an even bigger surprise with time was the fact that this system, in spite of its apparent simplicity, is a host of many phase transitions and phenomena, which still challenge both theorists and experimentalists alike, and very likely a few more surprises are in store for us. In this talk I will present an overview of some of the theoretical efforts devoted to this system and I will refer to the available experimental results when appropriate.

Host: Eddy Timmermans