Warm Dark Matter from keVins
  We propose a simple model for Warm Dark Matter (WDM) in which two fermions
are added to the Standard Model: (quasi-) stable "keVins" (keV inert fermions)
which account for WDM and their unstable brothers, the "GeVins" (GeV inert
fermions), both of which carry zero electric charge and lepton number, and are
(approximately) "inert", in the sense that their only interactions are via
suppressed couplings to the Z. We consider scenarios in which stable keVins are
thermally produced and their abundance is subsequently diluted by entropy
production from the decays of the heavier unstable GeVins. This mechanism could
be implemented in a wide variety of models, including E_6 inspired
supersymmetric models or models involving sterile neutrinos.
