REHEATING AND CAUSAL THERMODYNAMICS

The reheating process in inflationary universe models is considered as an out-of-equilibrium mixture of two interacting and reacting fluids, and studied within the framework of causal, irreversible thermodynami cs. The evolution of the temperature and the decay rate as determined by causal thermodynamics are estimated at different stages of the proc ess. A simple model is also used to find the perturbations of the expa nsion rate, including the possibility of damped oscillations.