The Subdominant Curvaton

TL;DR

This paper systematically studies how self-interacting curvaton models, including non-renormalizable potentials, can produce the observed primordial perturbations even when the curvaton is subdominant at decay, revealing complex dynamics and non-monotonous relations.

Contribution

It provides a comprehensive analysis of the amplitude of primordial perturbations in self-interacting curvaton models, highlighting the viability of subdominant curvatons with complex field dynamics.

Findings

Large parameter regions yield observed perturbations even with fast-diluting non-renormalizable potentials.

Subdominant curvatons by a factor of 10^-3 can still produce the observed perturbation.

Non-monotonous and oscillatory behaviors in perturbation evolution are observed in certain regimes.

Abstract

We present a systematic study of the amplitude of the primordial perturbation in curvaton models with self-interactions, treating both renormalizable and non-renormalizable interactions. In particular, we consider the possibility that the curvaton energy density is subdominant at the time of the curvaton decay. We find that large regions in the parameter space give rise to the observed amplitude of primordial perturbation even for non-renormalizable curvaton potentials, for which the curvaton energy density dilutes fast. At the time of its decay, the curvaton energy density may typically be subdominant by a relative factor of 10^-3 and still produce the observed perturbation. Field dynamics turns out to be highly non-trivial, and for non-renormalizable potentials and certain regions of the parameter space we observe a non-monotonous relation between the final curvature perturbation and the initial curvaton value. In those cases, the time evolution of the primordial perturbation also displays an oscillatory behaviour before the curvaton decay.