Gravitino Production in the Early Universe and Its Implications to Particle Cosmology

Abstract

Effects of the unstable gravitino on the big-bang nucleosynthesis (BBN) and its implications to particle cosmology are discussed. If the gravitino mass is smaller than \sim 20 TeV, lifetime of the gravitino becomes longer than \sim 1sec and its decay may spoil the success of the standard BBN. In order to avoid such a problem, upper bound on the reheating temperature after the inflation is obtained, which may be as low as \sim 10^{5-6} GeV. For a successful baryogenesis with such low reheating temeprature, a consistent scenario based on the large cutoff supergravity (LCSUGRA) hypothesis of supersymmetry breaking, where the gravitino and sfermion become as heavy as \sim O(1-10 TeV), is proposed. In the LCSUGRA, non-thermal leptogenesis can produce large enough baryon asymmetry. We also see that, in the LCSUGRA scenario, relic density of the lightest superparticle becomes consistent with the WMAP value of the dark matter density in the parameter region required for the successful non-thermal leptogenesis. In this case, the dark matter density may be reconstructed with the future e^+e^- linear collider.