On Metric Preheating

TL;DR

This paper investigates how super-horizon metric fluctuations evolve during preheating with a coupled scalar field, finding that inflationary predictions remain largely unaffected despite resonance effects.

Contribution

It demonstrates that efficient broad resonance during preheating does not significantly alter the standard inflationary metric perturbation predictions.

Findings

Super-horizon eltahi fluctuations are damped during inflation.

Inflationary predictions for metric perturbations remain robust.

Resonance effects do not strongly modify large-scale structure predictions.

Abstract

We consider the generation of super-horizon metric fluctuations during an epoch of preheating in the presence of a scalar field \chi quadratically coupled to the inflaton. We find that the requirement of efficient broad resonance is concomitant with a severe damping of super-horizon \delta\chi quantum fluctuations during inflation. Employing perturbation theory with backreaction included as spatial averages to second order in the scalar fields and in the metric, we argue that the usual inflationary prediction for metric perturbations on scales relevant for structure formation is not strongly modified.