Leptogenesis with GeV-Scale Right-Handed Neutrinos

We review the relation between leptogenesis and the discrete symmetry of charge-parity conjugation. The requirement of respecting the theorem of combined charge-parity-time reversal invariance at the level of the kinetic equations describing leptogenesis in the early Universe poses an interesting challenge that may most efficiently be addressed by the use of closed-time-path techniques. A byproduct of these methods is an accurate and unified description of leptogenesis from oscillations of right-handed neutrinos that applies to the regime of ultraheavy as well as GeV-scale RHNs. For the latter scenario, we discuss the mechanism on the example of the osicllatory and overdamped parametric regimes and very briefly comment on the prospect of experimental tests.