Large Spin-2 Signals at the Cosmological Collider

TL;DR

This paper explores how a nonzero chemical potential affects massive spin-2 fields during inflation, leading to enhanced signals in cosmological collider observables, especially in tensor modes.

Contribution

It introduces a unique parity-violating chemical potential operator for spin-2 fields, enabling large, detectable signals in cosmological collider experiments.

Findings

Chemical potential boosts tensor mode production for heavy spin-2 particles.

Large signals appear at tree-level in curvature trispectrum and tensor-curvature bispectrum.

The theory remains ghost-free with one scalar and two tensor modes.

Abstract

We study the theory and phenomenology of massive spin-2 fields during the inflation with nonzero background chemical potential, and extend the cosmological collider physics to tensor modes. We identify a unique dimension-5 and parity-violating chemical potential operator for massive spin-2 fields, which leads to a ghost-free linear theory propagating one scalar mode and two tensor modes. The chemical potential greatly boosts the production of one tensor mode even for very heavy spin-2 particles, and thereby leads to large and distinct cosmological collider signals for massive spin-2 particles. The large signals show up at the tree-level in both the curvature trispectrum and the tensor-curvature mixed bispectrum.