# Solid Soft Theorems

## TL;DR

This paper derives cosmological soft theorems for solids coupled to gravity, revealing unique anisotropic stress behaviors and extending the understanding of Maldacena's consistency relation to these models.

## Contribution

It introduces all cosmological adiabatic modes for solids with non-zero anisotropic stresses and derives related soft theorems, including tensor and vector cases, clarifying their gauge derivations.

## Key findings

- Maldacena's consistency relation holds only after angular averaging.
- Soft theorems for tensor and vector perturbations are established.
- Clarification of soft theorem derivations in gauges without residual diffeomorphisms.

## Abstract

We derive cosmological soft theorems for solids coupled to gravity. To this end, we first derive all cosmological adiabatic modes for solids, which display the interesting novelty of non-vanishing anisotropic stresses on large scales. Then, from the corresponding symmetries of the action of perturbations we compute the leading order related soft theorems using the operator product expansion. For the scalar bispectrum, we re-derive the result that Maldacena's consistency relation is recovered only upon angular averaging over the long mode direction. In addition, we find theorems for soft tensor and vector perturbations. In passing, we also clarify the derivation of these soft theorems in gauges where no residual diffeomorphisms exist.