Thermal Effects and Sudden Decay Approximation in the Curvaton Scenario

TL;DR

This paper examines how temperature-dependent decay rates of the curvaton affect primordial curvature perturbations, combining analytical and numerical methods to improve understanding of the decay process and its cosmological implications.

Contribution

It introduces a generalized transfer coefficient accounting for temperature effects and compares analytical predictions with numerical results in the curvaton decay scenario.

Findings

The transfer coefficient depends on the entropy ratio after decay.

Analytical expressions closely match numerical simulations.

Temperature effects significantly influence curvature perturbation predictions.

Abstract

We study the impact of a temperature-dependent curvaton decay rate on the primordial curvature perturbation generated in the curvaton scenario. Using the familiar sudden decay approximation, we obtain an analytical expression for the curvature perturbation after the decay of the curvaton. We then investigate numerically the evolution of the background and of the perturbations during the decay. We first show that the instantaneous transfer coefficient, related to the curvaton energy fraction at the decay, can be extended into a more general parameter, which depends on the net transfer of the curvaton energy into radiation energy or, equivalently, on the total entropy ratio after the complete curvaton decay. We then compute the curvature perturbation and compare this result with the sudden decay approximation prediction.