Zoology of Graviton non-Gaussianities

TL;DR

This paper explores how different symmetry breaking patterns in inflation models affect graviton non-Gaussianities, introducing an effective field theory for Solid Inflation with broken spatial diffeomorphisms.

Contribution

It characterizes graviton non-Gaussianities in models with broken de Sitter boosts and develops the EFT of Solid Inflation for the first time.

Findings

Solid Inflation allows the most freedom for graviton interactions.

Certain symmetry breaking patterns can sustain quasi de Sitter expansion.

Constructed the EFT of Solid Inflation with broken spatial diffeomorphisms.

Abstract

We characterize graviton non-Gaussianities in models of inflation where de Sitter boosts are spontaneously broken. We discuss which of the symmetry breaking patterns studied in Nicolis et al., 2015 can sustain a period of quasi de Sitter expansion, and show that the symmetry breaking pattern of Solid Inflation allows the most freedom for graviton interactions. We comment on the phenomenological consequences of some of these interactions. As a byproduct of this analysis we construct the "EFT of Solid Inflation", which has all the useful features of the EFT of Inflation but for the case of broken spatial diffeomorphisms.