Modulated preheating and isocurvature perturbations

TL;DR

This paper explores a modulated preheating model where a light scalar field influences inflaton coupling, producing observable curvature perturbations and non-Gaussianity, with implications for dark matter isocurvature constraints.

Contribution

It introduces a modulated preheating scenario that can generate significant curvature perturbations and non-Gaussianity, extending the understanding of primordial perturbation mechanisms.

Findings

Modulated preheating can produce the observed curvature perturbation.

The model can lead to larger non-Gaussianity than modulated reheating.

Current isocurvature constraints limit the model's contribution to dark matter and primordial gravitational waves.

Abstract

We consider a model of preheating where the coupling of the inflaton to the preheat field is modulated by an additional scalar field which is light during inflation. We establish that such a model produces the observed curvature perturbation analogously to the modulated reheating scenario. The contribution of modulated preheating to the power spectrum and to non-Gaussianity can however be significantly larger compared to modulated perturbative reheating. We also consider the implications of the current constraints on isocurvature perturbations in case where the modulating field is responsible for cold dark matter. We find that existing bounds on CDM isocurvature perturbations imply that modulated preheating is unlikely to give a dominant contribution to the curvature perturbation and that the same bounds suggest important constraints on non-Gaussianity and the amount of primordial gravitational waves.