DAMPING OF HYDRODYNAMIC MODES IN A TRAPPED BOSE-GAS ABOVE THE BOSE-EINSTEIN TRANSITION-TEMPERATURE

We calculate the damping of low-lying collective modes of a trapped Bo se gas in the hydrodynamic regime, and show that this comes solely fro m the shear viscosity, since the contributions from bulk viscosity and thermal conduction vanish. The hydrodynamic expression for the dampin g diverges due to the failure of hydrodynamics in the outer parts of t he cloud, and we take this into account by a physically motivated cuto ff procedure. Our analysis of available experimental data indicates th at higher densities than have yet been achieved are necessary for inve stigating hydrodynamic modes above the Bose-Einstein transition temper ature.