  The time dependence of the temperature during the reheating process is
studied. We consider the thermal feedback effects of the produced particles on
the effective dissipation rate of the inflaton field, which can lead to
enhanced production of particles. We parameterize the temperature dependence of
the dissipation rate in terms of a Taylor expansion containing the vacuum decay
rate and the thermal terms. By solving the Boltzmann equations for the energy
densities of the inflaton and radiation, we provide analytic estimates for a
general power law dependence on the temperature. In this way we describe the
entire reheating process. The maximum temperature of the reheating process and
its dependence on model parameters are studied in different cases. The impact
of the thermal feedback effects on the expansion history of the universe and
the cosmic microwave background (CMB) is discussed. We also discuss the range
of validity of our approach.
