  We analyze theoretically the transport properties of a weakly-interacting
ultracold Bose gas enclosed in two reservoirs connected by a constriction. We
assume that the transport of the superfluid part is hydrodynamic, and we
describe the ballistic transport of the normal part using the Landauer-Buttiker
formalism. Modeling the coupled evolution of the phase, atom number, and
temperature mismatches between the reservoirs, we predict that Helmholtz
(plasma) oscillations, induced by an initial imbalance in atom numbers, can be
observed at non-zero temperatures below Tc. We show that, because of its strong
compressibility, the ultracold Bose gas is characterized by a fast
thermalization compared to the damping time for plasma oscillations,
accompanied by a fast transfer of the normal component through the
constriction. This fast thermalization also affects the gas above Tc, where we
present an explicit comparison to the ideal fermionic case.
