  Neutrino-neutrino interactions, as mediated by standard model Z exchange, can
drastically enhance the Dodelson-Widrow mechanism for the production of sterile
neutrinos in the region of temperature $5-15$MeV. For a sterile mass in the KeV
region with the usual type of active-sterile neutrino coupling, the production
can be copious enough to provide ample dark matter, even when the
active-sterile coupling is small enough to avoid the bounds set by laboratory
results.
