Non-Gaussianity in the modulated reheating scenario

TL;DR

This paper analyzes the non-Gaussian features of primordial curvature perturbations in the modulated reheating scenario, providing formulas for non-linear parameters and exploring their relationships.

Contribution

It derives expressions for non-Gaussianity parameters in the modulated reheating scenario using the $ ext{delta}N$ formalism, including new inequalities between these parameters.

Findings

$g_{NL}$ is at least as large as $f_{NL}$ when certain conditions are met.

Provides a general inequality between $f_{NL}$ and $ au_{NL}$ applicable to various inflationary models.

Offers explicit formulas for bispectrum and trispectrum non-Gaussianity parameters.

Abstract

We investigate the non-Gaussianity of primordial curvature perturbation in the modulated reheating scenario where the primordial perturbation is generated due to the spacial fluctuation of the inflaton decay rate to radiation. We use the $\delta N$ formalism to evaluate the trispectrum of curvature perturbation as well as its bispectrum. We give expressions for three non-linear parameters $f_{NL}, \tau_{NL}$ and $g_{NL}$ in the modulated reheating scenario. If the intrinsic non-Gaussianity of scalar field fluctuations and third derivative of the decay rate with respect to scalar fields are negligibly small, $g_{NL}$ has at least the same order of magnitude as $f_{NL}$. We also give general inequality between $f_{NL}$ and $\tau_{NL}$ which is true for other inflationary scenarios as long as primordial non-Gaussianity comes from super-horizon evolution.