A particle-dynamics study of dissipation in colliding clouds of ultracold fermions

We present a numerical study of the micro–dynamical roots of dissipation in two colliding mesoscopic clouds of point–like fermions as a function of the scattering length and of temperature approaching full quantum degeneracy. This study, which is motivated by current experiments on ultracold gaseous mixtures of fermionic atoms inside magnetic traps, combines the solution of the coupled Vlasov—Landau equations for the Wigner distribution functions with a locally adaptive importance–sampling technique for handling collisional interactions. The results illustrate the consequences of genuinely quantum collisional phenomena, and in particular the role of Pauli blocking in the transition to hydrodynamic behaviour. We also compare the computed quantum collision rate as a function of temperature in the weak–coupling case with theoretical results assuming that equilibrium distributions determine the quantum collision integral