Viscous dynamics of a quenched trapped dipolar Fermi gas

We consider collective motion and damping of dipolar Fermi gases in the hydrodynamic regime. We investigate the trajectories of collective oscillations—here dubbed “weltering” motions—in cross-dimensional rethermalization experiments via Monte Carlo simulations, where we find stark differences from the dilute regime. These observations are interpreted within a semiempirical theory of viscous hydrodynamics for gases confined to anisotropic harmonic potentials. The derived equations of motion provide a simple effective theory that show favorable agreement with full numerical solutions. To do so, the theory must carefully account for the size and shape of the effective volume within which the gas’s behavior is hydrodynamic. Although formulated for close-to-threshold dipolar collisions, our theoretical framework can be repurposed for other elastic cross sections in future studies.