Dark matter self-interactions from spin-2 mediators
  We propose a new mechanism for rendering dark matter self-interacting in the
presence of a massive spin-2 mediator. The derived Yukawa-type potential for
dark matter is independent of the spins of dark matter in the leading order of
the momentum expansion, so are the resulting non-perturbative effects for the
dark matter self-scattering. We find that both the Born cross section and
relatively mild resonance effects assist to make the self-scattering cross
section velocity-dependent. We discuss how to evade the current indirect bounds
on dark matter annihilations and show that the model is marginally compatible
with perturbative unitarity in the ghost-free realization of the massive spin-2
particle.
