Singlet portal extensions of the standard seesaw models to dark sector
  with local dark symmetry: An alternative to the new minimal standard model
  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 $\sim 0.08$ (resulting in
$N_{\rm eff} = 3.130$ the effective number of neutrino species), Higgs
inflation, small and large scale structure formation, and current relic density
of scalar DM ($X$). The Higgs signal strength is equal to one as in the SM for
unbroken $U(1)_X$ case with a scalar dark matter, but it could be less than one
independent of decay channels if the dark matter is a dark sector fermion or if
$U(1)_X$ is spontaneously broken, because of a mixing with a new neutral scalar
boson in the models.
