DBI Galileon in the Effective Field Theory of Inflation: Orthogonal non-Gaussianities and constraints from the Trispectrum

TL;DR

This paper explores a specific inflationary model, Dirac-Born-Infeld Galileon inflation, analyzing its non-Gaussian features, especially the trispectrum, and discusses observational constraints on its parameters.

Contribution

It formulates the DBI Galileon inflation within the effective field theory framework and computes the trispectrum, revealing new shapes from higher-derivative operators.

Findings

Calculated the trispectrum for the model.

Identified unique shapes in the trispectrum.

Discussed observational bounds on model parameters.

Abstract

Very few explicit inflationary scenarios are known to generate a large bispectrum of orthogonal shape. Dirac-Born-Infeld Galileon inflation, in which an induced gravity term is added to the DBI action, is one such model. We formulate it in the language of the effective field theory of inflation by identifying the unitary gauge operators that govern the behavior of its cosmological fluctuations. We show how to recover rather easily from this its power spectrum and bispectrum, which we calculated previously using standard cosmological perturbation theory. We push our calculations up to the determination of the fourth-order action and of the trispectrum, in which shapes absent in k-inflation arise due to the presence of higher-order derivative operators. We finally discuss the combined constraints set on this model by current observational bounds on the bispectrum and trispectrum.