Breakdown of the semiclassical approximation during the early stages of preheating

TL;DR

This paper investigates the limits of the semiclassical approximation during early preheating in chaotic inflation models, showing it breaks down before scattering or backreaction effects become significant.

Contribution

It introduces a modified criterion for the validity of the semiclassical approximation and demonstrates its failure during the initial stages of preheating.

Findings

Semiclassical approximation breaks down early in preheating

Large fluctuations in quantum field two-point functions occur

Validity criterion predicts breakdown before scattering effects

Abstract

The validity of the semiclassical approximation is investigated during the preheating phase in models of chaotic inflation using a modification of a criterion previously proposed for semiclassical gravity. If the modified criterion is violated then fluctuations of the two-point function for the quantum fields are large and the semiclassical approximation is not valid. Evidence is provided that the semiclassical approximation breaks down during the early stages of preheating, well before either scattering effects or backreaction effects are important.