Leptogenesis-MNS Link in Unified Models with Natural Neutrino Mass Hierarchy

We discuss the relation between leptogenesis and the MNS phases in the class of see-saw models called light sequential dominance in which the right-handed neutrinos dominate sequentially, with the dominant right-handed neutrino being the lightest one. The heaviest right-handed neutrino then decouples, leaving effectively two right-handed neutrinos. Light sequential dominance is motivated by $SO(10)$ models which predict three right-handed neutrinos. With an approximate Yukawa texture zero in the 11 position there are only two see-saw phases which are simply related to the MNS phase measurable at a neutrino factory and the leptogenesis phase. The leptogenesis phase is predicted to be equal to the neutrinoless double beta decay phase.