On the generation of a non-gaussian curvature perturbation during preheating

Abstract

The perturbation of a light field might affect preheatingand hence generate a contribution to the spectrum and non-gaussianity ofthe curvature perturbation ζ. The field might appear directly in the preheatingmodel (curvaton-type preheating) or indirectly through its effect on amass or coupling (modulated preheating).We give general expressions for ζ based on the δN formula, and apply them to the cases of quadratic and quarticchaotic inflation. For the quadratic case, curvaton-type preheating is ineffective in contributing to ζ, but modulated preheating can be effective. For quartic inflation, curvaton-typepreheating may be effective but the usual δN 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.