| We study dynamics of impurity immersed in superfluid quantum liquid in terms of collective variables. The interactions with background phonons are shown to have a universal form for sufficiently low temperature/ frequency of external perturbation. For continuous spectrum of the phonons the later can be integrated out leading to effective action containing dissipation and noise terms. We then consider motion of a particle under constant external force and show that it performs damped Bloch oscillation. |
|