Modulated curvaton decay

TL;DR

This paper investigates how the decay of a curvaton field, modulated by another field, generates primordial density perturbations and non-Gaussianity, unifying curvaton and modulated reheating models.

Contribution

It introduces a model of modulated curvaton decay, calculates resulting density perturbations and non-Gaussianity, and verifies the Suyama-Yamaguchi inequality in this context.

Findings

Standard curvaton and modulated reheating results recovered as limits.

Derived conditions for the Suyama-Yamaguchi inequality saturation.

Provided a unified framework for density perturbation generation mechanisms.

Abstract

We study primordial density perturbations generated by the late decay of a curvaton field whose decay rate may be modulated by the local value of another isocurvature field, analogous to models of modulated reheating at the end of inflation. We calculate the primordial density perturbation and its local-type non-Gaussianity using the sudden-decay approximation for the curvaton field, recovering standard curvaton and modulated reheating results as limiting cases. We verify the Suyama-Yamaguchi inequality between bispectrum and trispectrum parameters for the primordial density field generated by multiple field fluctuations, and find conditions for the bound to be saturated.