Co-Interacting Dark Matter

Understand

We propose a novel mechanism with two component dark matter models.

• The subdominant dark matter can thermalize the dominant one in galaxies, and leads to core density profiles.
• Using ultralight dark photons and $\mathrm{GeV}$-$\mathrm{TeV}$ Dirac fermions as an example, we couple the two dark matter candidates with a $U(1)$ interaction.
• This mechanism differs from self-interacting dark matter, due to three effects: (1) higher occupation numbers, (2) forward-backward scattering cancellation, and (3) the multiple scatterings required for the heavy dark matter.