Primordial non-Gaussianity from G-inflation

TL;DR

This paper explores the generation of primordial fluctuations in G-inflation models, analyzing their power spectrum and non-Gaussian features, revealing richer phenomenology than traditional single-field inflation.

Contribution

It provides a comprehensive analysis of primordial fluctuations in G-inflation, including power spectrum and bispectrum calculations with general parameter dependence.

Findings

Power spectrum computed with non-slow-roll effects

Bispectrum analysis reveals non-Gaussian amplitude dependence on sound speed

G-inflation models exhibit richer phenomenology than standard inflation

Abstract

We present a comprehensive study of primordial fluctuations generated from G-inflation, in which the inflaton Lagrangian is of the form $K(\phi, X)-G(\phi, X)\Box\phi$ with $X=-(\partial\phi)^2/2$. The Lagrangian still gives rise to second-order gravitational and scalar field equations, and thus offers a more generic class of single-field inflation than ever studied, with a richer phenomenology. We compute the power spectrum and the bispectrum, and clarify how the non-Gaussian amplitude depends upon parameters such as the sound speed. In so doing we try to keep as great generality as possible, allowing for non slow-roll and deviation from the exact scale-invariance.