keV Sterile Neutrino Dark Matter and Neutrino Model Building
  A sterile neutrino with a mass around the keV scale could be an interesting
candidate for warm dark matter. Although there are several scenarios and
production mechanisms known in which such a particle could yield the correct
abundance, there are astonishingly few models around that can actually yield an
explanation for the appearance of a keV-like scale. We here review three main
classes of such mass models for keV sterile neutrino dark matter, based on
split seesaw, on L_e - L_\mu - L_\tau\ symmetry, and on the Froggatt-Nielsen
mechanism, respectively.
