Delayed Reheating and the Breakdown of Coherent Oscillations

TL;DR

This paper investigates the evolution of inflaton perturbations after inflation, revealing that coherent oscillations break down earlier than previously thought, affecting models of the early universe and gravitational wave production.

Contribution

It provides accurate analytic approximations for post-inflationary perturbations and shows that oscillations break down before the universe becomes radiation dominated.

Findings

Coherent oscillations break down before radiation domination.

Breakdown occurs at the length scale of the post-inflationary horizon.

Implications for gravitational wave background generation.

Abstract

We analyze the evolution of the perturbations in the inflaton field and metric following the end of inflation. We present accurate analytic approximations for the perturbations, showing that the coherent oscillations of the post-inflationary condensate necessarily break down long before any current phenomenological constraints require the universe to become radiation dominated. Further, the breakdown occurs on length-scales equivalent to the comoving post-inflationary horizon size. This work has implications for both the inflationary "matching" problem, and the possible generation of a stochastic gravitational wave background in the post-inflationary universe.