Recently, an alternative to cold dark matter has been proposed in which a vector field (`dipolar dark matter') is coupled to an effective composite metric in massive bigravity. This theory is classically ghost free, and has a finite strong coupling scale. Here, the decoupling limit of this theory is derived, which gives a stable EFT which should be valid much below the strong coupling scale.

EFTs of dark matter are becoming increasingly popular as we try to better model and understand galactic phenomenology. Here, the ghost freedom in massive bigravity is used to infer a valid low energy EFT for vector dark matter, which provides an interesting alternative to many conventional cold dark matter models.