Two-step strongly first-order electroweak phase transition modified FIMP dark matter, gravitational wave signals, and the neutrino mass

We study a dynamical freeze-in production of the dark matter considering the electroweak phase transition history of the Universe. The kinematical thresholds of the decay and scattering processes for the dark matter production can be altered by the temperature dependent thermal masses of particles, which might lead to enhancement or reduction of the dark matter relic abundance. The second-stage strongly first-order electroweak phase transition (SFOEWPT) triggered by the hidden scalars can be probed at colliders and the gravitational wave detectors. The two-step SFOEWPT modified late decay FIMP dark matter is accomplished with a Dirac neutrino mass explanation in the scotogenic model.