title: Collisions in zero temperature Fermi gases.
abstract: We examine the collisional behavior of two-component Fermi gases released at zero temperature from a harmonic trap. Using a phase-space formalism to calculate the collision rate during expansion, we find that Pauli blocking plays only a minor role for momentum changing collisions. As a result, for a large scattering cross section, Pauli blocking will not prevent the gas from entering the collisionally hydrodynamic regime. In contrast to the bosonic case, hydrodynamic expansion at very low temperatures is therefore not evidence for fermionic superfluidity.
authors.affiliation: Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, MIT, Cambridge, Massachusetts 02139, USA.
authors.forename: Subhadeep
authors.initials: S
authors.lastname: Gupta
authors.forename: Zoran
authors.initials: Z
authors.lastname: Hadzibabic
authors.forename: James R
authors.initials: JR
authors.lastname: Anglin
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Ketterle