Self-interacting Spin-2 Dark Matter

TL;DR

This paper proposes a new light spin-2 dark matter candidate within bigravity theories, highlighting its self-interactions and potential to address small-scale structure issues in cosmology.

Contribution

It introduces an elementary spin-2 dark matter model with specific interaction properties and explores its implications for cosmological structure formation.

Findings

Dark matter candidate is light and self-interacting.

Self-annihilation via 3-to-2 processes is significant.

Parameter space regions can resolve small-scale structure problems.

Abstract

Recent developments in bigravity allow one to construct consistent theories of interacting spin-2 particles that are free of ghosts. In this framework, we propose an elementary spin-2 dark matter candidate with a mass well below the TeV scale. We show that, in a certain regime where the interactions induced by the spin-2 fields do not lead to large departures from the predictions of general relativity, such a light dark matter particle typically self-interacts and undergoes self-annihilations via 3-to-2 processes. We discuss its production mechanisms and also identify the regions of the parameter space where self-interactions can alleviate the discrepancies at small scales between the predictions of the collisionless dark matter paradigm and cosmological N-body simulations.