Baryogenesis, Neutrino Masses, and Dynamical Dark Energy

This thesis discusses several models that connect different areas of particle physics and cosmology. The first of these is a baryogenesis model that creates the baryon asymmetry of our universe through the dynamics of a dark energy field, thereby illustrating that these two topics might be related. Afterwards, several neutrino mass models are discussed, which make use of an extra-dimensional setting to overcome certain problems of their four dimensional counterparts. The central discussion of this thesis concerns a leptogenesis model with many standard model singlets. Amongst other things, we show that the presence of these states can lower the standard bound for the necessary reheating temperature of the universe by at least one and a half orders of magnitude. For a further motivation of this scenario, we also discuss a concrete extra-dimensional model that can naturally yields many of the ingredients needed for leptogenesis with many singlets.