TEMPERATURE AT THE FIRST STAGE OF REHEATING IN INFLATIONARY COSMOLOGYWITHOUT SLOW ROLLING

We consider statistical properties of massive non-relativistic bosons arising at the first stage of reheating as a result of quantum decay o f a classical inflaton field. We use the cosmological model describing the dynamics of a transition from the inflationary stage to a quasi-d ust stage without imposing the slow-rolling hypothesis. In this framew ork, we apply statistics and find that the process of emerging of mass ive non-relativistic bosons at the first stage of reheating looks like evaporation of a Bose condensate. They are described by the equation of state for an ideal quantum degenerate Bose gas which has the Gibbon s-Hawking temperature related to the de Sitter event horizon.