REHEATING IN THE PRESENCE OF NOISE

Explosive particle production due to parametric resonance is a crucial feature of reheating in inflationary cosmology. Coherent oscillations of the inflaton field act as a periodically varying mass in the evolu tion equation for matter fields which couple to the inflaton. This in turn results in the parametric resonance instability. Thermal and quan tum noise will lead to a nonperiodic perturbation in the mass. We stud y the resulting equation for the evolution of matter fields and demons trate that noise (at least if it is temporally uncorrelated) will incr ease the rate of particle production. We also estimate the limits on t he magnitude of the noise for which the resonant behavior is qualitati vely unchanged.