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 evolution equation for
matter fields which couple to the inflaton. This in turn results in the
parametric resonance instability. Thermal and quantum noise will lead to a
nonperiodic perturbation in the mass. We study the resulting equation for the
evolution of matter fields and demonstrate that noise (at least if it is
temporally uncorrelated) will increase the rate of particle production. We also
estimate the limits on the magnitude of the noise for which the resonant
behavior is qualitatively unchanged.Comment: 26 pages, 2 figures, uses LATE
