Preheating and the non-gaussianity of the curvature perturbation

TL;DR

This paper investigates how preheating processes after inflation influence the curvature perturbation's spectrum and non-gaussianity, focusing on quadratic and quartic inflation models and different preheating mechanisms.

Contribution

It provides general expressions for curvature perturbation using the elta Normalism and analyzes their applicability to various inflation and preheating scenarios.

Findings

Modulated preheating can significantly contribute to urvature perturbationor quadratic inflation.

Curvaton-type preheating is ineffective for quadratic inflation but may be relevant for quartic inflation.

Modified elta Normalism is needed to analyze quartic inflation with curvaton-type preheating.

Abstract

The perturbation of a light field might affect preheating and hence generate a contribution to the spectrum and non-gaussianity of the curvature perturbation \zeta. The field might appear directly in the preheating model (curvaton-type preheating) or indirectly through its effect on a mass or coupling (modulated preheating). We give general expressions for \zeta based on the \delta N formula, and apply them to the cases of quadratic and quartic chaotic inflation. For the quadratic case, curvaton-type preheating is ineffective in contributing to \zeta, but modulated preheating can be effective. For quartic inflation, curvaton-type preheating may be effective but the usual \delta N formalism has to be modified. We see under what circumstances the recent numerical simulation of Bond et al. [0903.3407] may be enough to provide a rough estimate for this case. This paper is dedicated to the memory of Lev Kofman who died on 12th November 2009