Dark neutrinos as Cold Dark Matter

It is shown that heavy sterile neutrinos can be a consequence of a new broken U(1)X symmetry. This sterile symmetry is further speculated to be related to the conservation of the dark number associated with Dark Matter particles, corresponding to a dark neutrino mass mND⩾1keV with a high scale ⩾∼102GeV dark symmetry U(1)D breaking.