Observational signatures and non-Gaussianities of general single-field inflation

TLDR

The study investigates primordial scalar non‑Gaussianities in general single‑field inflationary models within Einstein gravity. The authors analyze models with an arbitrary inflaton Lagrangian and sound speed, deriving general expressions for non‑Gaussianities. The non‑Gaussianity is fully specified by five parameters, yielding distinct shapes that can be observable when the sound speed is small, and reproducing known results in special limits.

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 five 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.