Cosmological Problems in Supersymmetry Theories

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We studied the origin of matter-anti-matter asymmetry (baryogenesis), and the cosmological effects of unstable particles in the early universe in the frame of supersymmetry. theories.We investigated the Affleck-Dine (AD) mechanism as promising baryogenesis process taking account of finite temperature effect. The AD field is trapped far away from the origin by the negative thermal correction for a long time until the temperature of the universe becomes low enough. In some case, non-linear dynamics of Q-balls produced in the AD mechanism suppresses the baryon asymmetry crucially. However, it was found that there remains some parameter space for which the dynamics of Q-ball formation does not affect the baryon asymmetry and it is possible to generate the right amount of the baryon asymmetry. We also found that there exists a soliton-like solution called "I-ball" in theories of a real scalar field if the scalar potential satisfies some conditions.We studied the big-bang nucleosynthesis (BBN) with the long-lived unstable particle such as gravitino and moduli. If the lifetime of the unstable particle is longer than about 0.1 sec, its decay may cause non-thermal nuclear reactions during or after the BBN, altering the predictions of the standard BBN scenario. We paid particular attention to its hadronic decay modes and calculate the primordial abundances of the light elements. Using the result, we derived constraints on the primordial abundance of the unstable particle. We applied our results to the gravitino problem, and obtained upper bound on the reheating temperature after inflation.We investigated the MeV-scale reheating scenario wherein the thermalization of neutrinos could be insufficient. We paid particular attention to the oscillation effects on the thermalization processes of neutrinos and obtained the stringent constraint on the reheating temperature (〜2MeV).