Observational Signatures and Non-Gaussianities of General Single Field Inflation

TL;DR

This paper provides a comprehensive analysis of primordial non-Gaussianities in single field inflation models with arbitrary Lagrangians and sound speeds, identifying key parameters that determine observable signatures.

Contribution

It derives a general formula for non-Gaussianities in single field inflation with arbitrary kinetic terms and sound speeds, unifying previous results and highlighting observable features.

Findings

Non-Gaussianity determined by 5 parameters under general conditions.

Distinctive non-Gaussian shapes emerge in specific parameter limits.

Potential observability of non-Gaussian signatures with small sound speed.

Abstract

We perform a general study of primordial scalar non-Gaussianities in single field inflationary models in Einstein gravity. We consider models where the inflaton Lagrangian is an arbitrary function of the scalar field and its first derivative, and the sound speed is arbitrary. We find that under reasonable assumptions, the non-Gaussianity is completely determined by 5 parameters. In special limits of the parameter space, one finds distinctive ``shapes'' of the non-Gaussianity. In models with a small sound speed, several of these shapes would become potentially observable in the near future. Different limits of our formulae recover various previously known results.