A portal extension of the standard model with an unbroken local dark U(1)

Assuming dark matter is absolutely stable due to unbroken dark gauge symmetry and singlet operators are portals to the dark sector, we present a simple extension of the standard seesaw model that can accommodate all the cosmological observations as well as terrestrial experiments available as of now, including leptogenesis, extra dark radiation of ∼ 8% (resulting in N_eff = 3.130 the effective number of neutrino species), Higgs inflation, small and large scale structure formation, and current relic density of scalar dark matter (X). The Higgs signal strength is equal to one as in the standard model.