Baryogenesis and degenerate neutrinos

We bring the theoretical issue of whether two important cosmological demands, baryon asymmetry and degenerate neutrinos as hot dark matter, can be compatible in the context of the seesaw mechanism. While the canonical seesaw model with right-handed neutrinos is disregarded in this aspect, the triplet seesaw model is able to reconcile leptogenesis with almost degenerate Majorana neutrinos but with some unnatural arrangements of parameters. To remedy this, we propose a hybrid seesaw model with a heavy Higgs triplet and right-handed neutrinos.