Inflation and primordial non-Gaussianities of "generalized Galileons"

TL;DR

This paper develops cosmological perturbation theory for generalized Galileon models, analyzing their inflationary predictions and non-Gaussianities, revealing modifications to standard consistency relations and bispectrum shapes.

Contribution

It provides the first detailed calculation of primordial power spectrum and bispectrum for generalized Galileon theories, extending inflationary model analysis.

Findings

Modified tensor-to-scalar ratio consistency relation.

Bispectrum shapes similar to $k$-inflation.

Implications for inflationary observational signatures.

Abstract

We set up cosmological perturbation theory and study the cosmological implications of the so-called ``generalized Galileon'' developed in \cite{Deffayet:2011gz,horndeski}. This is the most general scalar field theory whose Lagrangian contains derivatives up to second order while keeping second order equations of motion, and contains as sub-cases $k$-inflation, $G$-inflation and many other models. We calculate the power spectrum of the primordial curvature perturbation, finding a modification of the usual consistency relation of the tensor-to-scalar ratio in $k$-inflation or perfect fluid models. Finally we also calculate the bispectrum, which contains no new shapes beyond those of $k$-inflation.