Freeze-In Dark Matter within the Seesaw mechanism
  We show that the minimal Type-I Seesaw mechanism can successfully account for
the observed dark matter abundance in the form of a keV sterile neutrino. This
population can be produced by the decay of the heavier neutral leptons, with
masses above the Higgs mass scale, while they are in thermal equilibrium in the
early Universe (freeze-in). Moreover, the implementation of the relevant
phenomenological constraints (relic abundance, indirect detection and structure
formation) on this model automatically selects a region of the parameter space
featuring an approximate lepton number symmetry.
