  The paper studies a Milne type problem for a linearized quantum Boltzmann
equation. Existence and uniqueness of the solution, together with asymptotic
properties are proven for a given energy flow. The energy flow is proportional
to the asymptotic limit of the mass flow, and the collision frequency is
aymptoticlaly cubic in velocity. The setting differs from the one for the
classical Boltzmann and related equations, where the fluid-dynamic mass flow
along half-line is constant. Here it is no more constant. Instead the study is
based on the energy flow which is no more fluid-dynamic, and on the entropy
flow which differs from the classical case.
