Loops in reheating and cosmological perturbations

TL;DR

This paper investigates how loop corrections during reheating in inflationary models, especially via parametric resonance, can significantly affect superhorizon curvature perturbations, potentially challenging perturbation theory validity.

Contribution

It reveals the impact of loop corrections during reheating on superhorizon perturbations, highlighting the breakdown of perturbation theory in resonance scenarios.

Findings

Loop corrections cause superhorizon evolution of curvature perturbations.

Parametric resonance during reheating amplifies these effects.

Perturbation theory may break down in resonance regimes.

Abstract

We show that in scalar field inflationary models, the loop corrections in reheating corresponding to the decay of the inflaton can cause nontrivial superhorizon evolution of the curvature perturbation. The effect turns out to be prominent when the decay occurs via parametric resonance, even indicating the breakdown of the perturbation theory, as we demonstrate in a specific model.