Search

We show that a gravitino with mass O( m w ) and a high reheat temperature after inflation, T R ≅10 12 −10 14 GeV, c an be compatible with cosmological constraints if the gravitino decays predominantly into neutrino-sneutrino pairs. Models in which the lightest supersymmetric particle is either the sneutrino or the neutralino are described. In this scenario, gravitino decay provides an alternative mechanism for producing supersymmetric dark matter, which may be either hot or cold.

Axiorecombination, e− + Z → (e−, Z) + a, is considered as a source of light pseudoscalar axions in stars. This process dominates the energy loss in axions for low-mass main-sequence stars, M ⪅ 0.2M ⊚ . For the sun, axiorecombination accounts for ∼ 1 4 of total axion flux at energies above ∼2 keV.

We discuss the evolution of neutrino beams in the presence of both flavor mixing and decays, and give a careful discussion of the implications of the supernova 1987A observations for neutrino mixing angles and lifetimes. Although the observation of electron antineutrinos from SN 1987A naively implies a lower bound on the electron neutrino lifetime τ ve >5.7×10 5 ( m ve eV )s, neutrino mixing must be taken into account when using this to place constraints on particle physics models with neutrino decay. In models with large mixing angles, a short lifetime for the neutrino with large electron neutrino component cannot be ruled out.