Natural chaotic inflation in supergravity and leptogenesis - art. no. 103514

We comprehensively investigate a chaotic inflation model proposed recently in the framework of supergravity. In this model, the form of Kahler potenti al is determined by a symmetry, that is. the Nambu-Goldstone-like shift sym metry, which guarantees the absence of the exponential factor in the potent ial for the inflaton field. Though we need the introduction of small parame ters, the smallness of the parameters is justified also by symmetries. That is, the zero limit of the small parameters recovers symmetries, which is n atural in the 't Hooft sense. The leptogenesis scenario via the inflaton de cay in this chaotic inflation model is also discussed. We find that the lep ton asymmetry enough to explain the present baryon number density is produc ed for low reheating temperatures avoiding the overproduction of gravitinos .