Shapes of non-Gaussianity in warm inflation

TL;DR

This paper investigates the non-Gaussian features of warm inflation models with sphaleron heating, focusing on the shape of the scalar three-point correlation function and its observational signatures.

Contribution

It computes the non-Gaussianity shape in warm inflation with sphaleron heating, identifying distinct features and proposing detection templates for observational searches.

Findings

Distinct non-Gaussian shapes in squeezed and folded limits.

Overlap of combined templates with non-Gaussian shape over a wide parameter range.

Predicted non-Gaussianity parameter |f_NL| between 0.7 and 50.

Abstract

Sphaleron heating has been recently proposed as a mechanism to realize warm inflation when inflaton is an axion coupled to pure Yang-Mills. As a result of heating, there is a friction coefficient $\gamma \propto T^3$ in the equation of motion for the inflaton, and a thermal contribution to cosmological fluctuations. Without the knowledge of the inflaton potential, non-Gaussianity is the most promising way of searching for the signatures of this model. Building on an earlier work by Bastero-Gil, Berera, Moss and Ramos, we compute the scalar three-point correlation function and point out some distinct features in the squeezed and folded limits. As a detection strategy, we show that the combination of the equilateral template and one new template has a large overlap with the shape of non-Gaussianity over the range $0.01 \leq\gamma/H\leq 1000$, and in this range $0.7 <|f_{\rm NL}| < 50$.