Damping in dilute Bose gases: A mean-field approach

Damping in a dilute Bose gas is investigated using a mean-field approximation which describes the coupled oscillations of condensate and noncondensate atoms in the collisionless regime. Explicit results for both Landau and Beliaev damping rates are given for nonuniform gases. In the case of uniform systems, we obtain results for the damping of phonons both at zero and finite temperature. The isothermal compressibility of a uniform gas is also discussed.