  We study the motion of a heavy tracer particle weakly coupled to a dense
ideal Bose gas exhibiting Bose-Einstein condensation. In the so-called
mean-field limit, the dynamics of this system approaches one determined by
nonlinear Hamiltonian evolution equations describing a process of emission of
Cerenkov radiation of sound waves into the Bose-Einstein condensate along the
particle's trajectory. The emission of Cerenkov radiation results in a friction
force with memory acting on the tracer particle and causing it to decelerate
until it comes to rest.
