# Dipolar Dark Matter as an Effective Field Theory

## TL;DR

This paper investigates a dipolar dark matter model within massive bigravity theory, demonstrating its ghost-free nature in the decoupling limit and establishing its validity as an effective field theory.

## Contribution

It provides the first detailed analysis of the decoupling limit of dipolar dark matter in bigravity, confirming its ghost-free status and effective field theory consistency.

## Key findings

- Decoupling limit is free of ghosts.
- Model is consistent as an effective field theory.
- Supports viability of dipolar dark matter in bigravity.

## Abstract

Dipolar Dark Matter (DDM) is an alternative model motivated by the challenges faced by the standard cold dark matter model to describe the right phenomenology at galactic scales. A promising realisation of DDM was recently proposed in the context of massive bigravity theory. The model contains dark matter particles, as well as a vector field coupled to the effective composite metric of bigravity. This model is completely safe in the gravitational sector thanks to the underlying properties of massive bigravity. In this work we investigate the exact decoupling limit of the theory, including the contribution of the matter sector, and prove that it is free of ghosts in this limit. We conclude that the theory is acceptable as an Effective Field Theory below the strong coupling scale.