Note on Thermalization of Non-resonantly Produced Sterile Neutrinos
  Using an analytic treatment, we discuss the parameter regions of large
active-sterile neutrino mixing angles where sterile neutrinos produced in
non-resonant flavour oscillations can approach thermalization in several
cosmologies. We show that thermalization affects only large active-sterile
neutrino mixing already rejected by different limits. Hence, the allowed
sterile neutrino parameter regions are unaffected.
