Leptogenesis with linear, inverse or double seesaw

The left-right symmetric model with doublet and bi-doublet Higgs scalars can accommodate linear, inverse or double seesaw for generating small neutrino masses in the presence of three singlet fermions. If the singlet fermions have small Majorana masses, they can form three pairs of quasi-degenerately Majorana fermions with three right-handed neutrinos. The decays of the quasi-degenerately Majorana fermions can realize the resonant leptogenesis. Alternatively, the right-handed neutrinos can obtain seesaw suppressed Majorana masses if the singlet fermions are very heavy. In this case, the leptogenesis with or without resonant effect is available in the decays of the right-handed neutrinos