Partially Massless Fields During Inflation

TL;DR

This paper explores the unique signatures of partially massless fields during inflation, revealing their potential to violate standard inflationary consistency relations and offering new detection avenues in cosmological data.

Contribution

It analyzes the couplings of partially massless fields to inflationary perturbations and identifies distinctive signatures in cosmological correlators that differ from those of massive fields.

Findings

Partially massless fields can violate the tensor consistency relation.

Exchange of these fields enhances the scalar trispectrum.

They do not contribute to the scalar bispectrum.

Abstract

The representation theory of de Sitter space allows for a category of partially massless particles which have no flat space analog, but could have existed during inflation. We study the couplings of these exotic particles to inflationary perturbations and determine the resulting signatures in cosmological correlators. When inflationary perturbations interact through the exchange of these fields, their correlation functions inherit scalings that cannot be mimicked by extra massive fields. We discuss in detail the squeezed limit of the tensor-scalar-scalar bispectrum, and show that certain partially massless fields can violate the tensor consistency relation of single-field inflation. We also consider the collapsed limit of the scalar trispectrum, and find that the exchange of partially massless fields enhances its magnitude, while giving no contribution to the scalar bispectrum. These characteristic signatures provide clean detection channels for partially massless fields during inflation.