Sterile neutrino hot, warm, and cold dark matter - art. no. 023501

We calculate the incoherent resonant and non-resonant scattering production of sterile neutrinos in the early universe. We find ranges of sterile neut rino masses, vacuum mixing angles, and initial lepton numbers which allow t hese species to constitute viable hot, warm, and cold dark matter (HDM, WDM , CDM) candidates which meet observational constraints. The constraints con sidered here include energy loss in core collapse supernovae, energy densit y limits at big bang nucleosynthesis, and those stemming from sterile neutr ino decay: limits from observed cosmic microwave background anisotropies, d iffuse extragalactic background radiation, and Li-6/D overproduction. Our c alculations explicitly include matter effects, both effective mixing angle suppression and enhancement (MSW resonance), as well as quantum damping. We for the first time properly include all finite temperature effects, diluti on resulting from the annihilation or disappearance of relativistic degrees of freedom, and the scattering-rate-enhancing effects of particle-antipart icle pairs (muons, tauons, quarks) at high temperature in the early univers e.