Scalar condensate decay in a fermionic heat bath in the early universe

Abstract

We consider one-loop thermal effects on the decay of a scalar field zero mode initially dominating the energy density of the universe. We assume fermionic decay channels and take into account the effects due to both particle and hole excitations, and present approximate expressions for the absorption and decay rates. We apply the results to the inflaton and solve the Boltzmann equations to find the temperature evolution of the fermionic plasma. We show that the reheat temperature can be greater than the inflaton mass if the inflaton decays into more than one fermionic species.