Temperature at the first stage of reheating in inflationary cosmology without slow rolling

We consider statistical properties of massive non-relativistic bosons arising at the first stage of reheating as a result of quantum decay of a classical inflaton field. We use the cosmological model describing the dynamics of a transition from the inflationary stage to a quasi-dust stage without imposing the slow-rolling hypothesis. In this framework, we apply statistics and fmd that the process of emerging of massive 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 Gibbons-Hawking temperature related to the de Sitter event horizon.