Strongly self-interacting vector dark matter via freeze-in

Understand

We study a vector dark matter (VDM) model in which the dark sector couples to the Standard Model sector via a Higgs portal.

• If the portal coupling is small enough the VDM can be produced via the freeze-in mechanism.
• It turns out that the electroweak phase transition have a substantial impact on the prediction of the VDM relic density.
• We further assume that the dark Higgs boson which gives the VDM mass is so light that it can induce strong VDM self-interactions and solve the small-scale structure problems of the Universe.