Modulated reheating by curvaton

TL;DR

This paper investigates a combined model of curvaton and modulated reheating mechanisms, analyzing how quantum fluctuations of a light scalar field influence curvature perturbations, non-linearity parameters, and observable cosmological ratios.

Contribution

It introduces a model where a light scalar field acts both as a curvaton and induces modulated reheating, exploring their combined effects on cosmological perturbations.

Findings

Non-linearity parameters can be significantly enhanced due to cancellation effects.

Both tensor-to-scalar ratio and non-linearity parameters can be large in simple quadratic models.

The model predicts observable signatures that could distinguish it from other inflationary scenarios.

Abstract

There might be a light scalar field during inflation which is not responsible for the accelerating inflationary expansion. Then, its quantum fluctuation is stretched during inflation. This scalar field could be a curvaton, if it decays at a late time. In addition, if the inflaton decay rate depends on the light scalar field expectation value by interactions between them, density perturbations could be generated by the quantum fluctuation of the light field when the inflaton decays. This is modulated reheating mechanism. We study curvature perturbation in models where a light scalar field does not only play a role of curvaton but also induce modulated reheating at the inflaton decay. We calculate the non-linearity parameters as well as the scalar spectral index and the tensor-to-scalar ratio. We find that there is a parameter region where non-linearity parameters are also significantly enhanced by the cancellation between the modulated effect and the curvaton contribution. For the simple quadratic potential model of both inflaton and curvaton, both tensor-to-scalar ratio and nonlinearity parameters could be simultaneously large.