  In the present paper we consider the motion of a very heavy tracer particle
in a medium of a very dense, non-interacting Bose gas. We prove that, in a
certain mean-field limit, the tracer particle will be decelerated and come to
rest somewhere in the medium. Friction is caused by emission of Cerenkov
radiation of gapless modes into the gas. Mathematically, a system of semilinear
integro-differential equations, introduced in [FSSG10], describing a tracer
particle in a dispersive medium is investigated, and decay properties of the
solution are proven. This work is an extension of [FGS10]; it is an extension
because no weak coupling limit for the interaction between tracer particle and
medium is assumed. The technical methods used are dispersive estimates and a
contraction principle.
