Leptogenesis in Theories with Large Extra Dimensions

We study the scenario of baryogenesis through leptogenesis in higher-dimensional theories, in which the scale of quantum gravity may be as low as few TeV. The minimal realization of these theories includes an isosinglet neutrino which is considered to propagate in large compact dimensions, whereas all the SM particles are localized on a (1+3)-dimensional wall. In the formulation of minimal leptogenesis models, we pay particular attention to the existence of Majorana spinors in higher dimensions. After compactification of the extra dimensions, we obtain a tower of Majorana Kaluza-Klein excitations which act as an infinite series of CP-violating resonators, and derive the necessary conditions for their constructive interference. Based on this CP-violating mechanism, we find that out-of-equilibrium decays of heavy Majorana excitations having masses above the critical temperature of the electroweak phase transition can produce a leptonic asymmetry which is reprocessed into the observed baryonic asymmetry of the Universe via unsuppressed sphaleron interactions.