Primordial Non-Gaussianity from G-inflation

TL;DR

This paper investigates the non-Gaussian features of primordial curvature perturbations in G-inflation models, calculating the non-Gaussianity parameter and analyzing its implications for secondary gravitational waves and black hole formation.

Contribution

It provides a numerical analysis of the bispectrum and non-Gaussianity parameter in G-inflation, confirming the consistency relation and showing small non-Gaussianity at peak scales.

Findings

f_NL remains small at peak scales despite large values elsewhere

The non-Gaussianity contributions to secondary gravitational waves are negligible

Consistency relation holds in G-inflation models

Abstract

Enormous information about interactions is contained in the non-Gaussianities of the primordial curvature perturbations, which are essential to break the degeneracy of inflationary models. We study the primordial bispectra for G-inflation models predicting both sharp and broad peaks in the primordial scalar power spectrum. We calculate the non-Gaussianity parameter $f_{\mathrm{NL}}$ in the equilateral limit and squeezed limit numerically, and confirm that the consistency relation holds in these models. Even though $f_{\mathrm{NL}}$ becomes large at the scales before the power spectrum reaches the peak and the scales where there are wiggles in the power spectrum, it remains to be small at the peak scales. Therefore, the contributions of non-Gaussianity to the scalar induced secondary gravitational waves and primordial black hole abundance are expected to be negligible.