The squeezed limit of the solid inflation three-point function

TL;DR

This paper confirms the anisotropic quadrupolar form of the scalar three-point function in solid inflation's squeezed limit, introduces a simple computation method, and derives new squeezed limit results involving vector and tensor perturbations.

Contribution

It provides a straightforward derivation of the three-point function in solid inflation and extends the analysis to include vector and tensor perturbations in the squeezed limit.

Findings

The three-point function has a quadrupolar anisotropic shape.

The system violates standard consistency relations.

New squeezed limit results for vector and tensor correlators.

Abstract

The recently proposed model of 'solid inflation' features a peculiar three-point function for scalar perturbations with an anisotropic, purely quadrupolar, squeezed limit. We confirm this result as well as the overall amplitude of the three point-function via an extremely simple computation, where we focus on the squeezed limit from the start and follow the standard logic adopted in deriving the consistency relations. Our system violates the consistency relations, but in the squeezed limit the three-point function can still be traded for a background-dependent two-point function, which is immediate to compute. Additionally, we use these simple methods to derive some new results - namely, certain squeezed limits of the three-point correlators involving vector and tensor perturbations as well.