MeV-scale reheating temperature and cosmological production of light
  sterile neutrinos
  We investigate how sterile neutrinos with a range of masses influence
cosmology in MeV-scale reheating temperature scenarios. By computing the
production of sterile neutrinos through the combination of mixing and
scattering in the early Universe, we find that light sterile neutrinos, with
masses and mixings as inferred from short-baseline neutrino oscillation
experiments, are consistent with big-bang nucleosynthesis (BBN) and cosmic
microwave background (CMB) radiation for the reheating temperature of ${\cal
O}(1)$ MeV if the parent particle responsible for reheating decays into
electromagnetic components (radiative decay). In contrast, if the parent
particle mainly decays into hadrons (hadronic decay), the bound from BBN
becomes more stringent. In this case, the existence of the light sterile
neutrinos can be cosmologically excluded, depending on the mass and the
hadronic branching ratio of the parent particle.
