Gravitational Effects on Inflaton Decay

TL;DR

This paper investigates how the inflaton field interacts gravitationally with matter and gravitons during the post-inflation oscillation phase, revealing particle production mechanisms and effects of non-minimal couplings.

Contribution

It demonstrates that gravitational couplings lead to particle production during inflaton oscillations and extends the analysis to models with non-minimal inflaton-gravity couplings.

Findings

Inflaton couples to matter and gravitons via gravitational oscillations.

Particle production is most efficient immediately after inflation.

Non-minimal couplings cause more violent oscillations but do not induce inflaton decay into gravitons.

Abstract

We point out that the inflaton inevitably couples to all non-conformally coupled matters gravitationally through an oscillation in the Hubble parameter or the cosmic scale factor. It leads to particle production during the inflaton oscillation regime, which is most efficient just after inflation. Moreover, the analysis is extended to the model with non-minimal inflaton couplings to gravity, in which the Hubble parameter oscillates more violently. We apply our results to the graviton production by the inflaton: gravitons are also produced just after inflation, but the non-minimal coupling does not induce inflaton decay into the graviton pair.