Cosmological Reheating and Self-Interacting Final State Bosons

We consider inflaton decay to final state bosons with self-interactions of moderate strength. We find that such final state self-interactions qualitatively alter the reheat dynamics. In the case of narrow-band resonance decay, where a quantitative analysis is possible, we show that these final state interactions regulate the decay rate. The phenomenon of parametric amplification is then effectively suppressed, and does not drastically enhance the decay rate and reheat temperature. Detailed applications of our results to realistic classes of inflationary models will be considered elsewhere.