Neutrino phenomenology, dark energy and leptogenesis from pseudo-Nambu-Goldstone bosons

We consider a model of dynamical neutrino masses via the see-saw mechanism. Nambu-Goldstone bosons (majorons) arise associated with the formation of the heavy right-handed Majorana masses. These bosons then acquire naturally soft masses (become pNGB's) at loop level via the Higgs-Yukawa mass terms. These models, like the original neutrino pNGB quintessence schemes of the 1980's [C.T. Hill, D.N. Schramm, J.N. Fry, Nucl. Part. Phys. 19 (1989) 25; J.A. Frieman, C.T. Hill, R. Watkins, Phys. Rev. D 46 (1992) 1226; A.K. Gupta, C.T. Hill, R. Holman, E.W. Kolb, Phys. Rev. D 45 (1992) 441; J.A. Frieman, C.T. Hill, A. Stebbins, I. Waga, Phys. Rev. Lett. 75 (1995) 2077, astro-ph/9505060] that proceed through the Dirac masses, are natural, have cosmological implications through mass varying neutrinos, long range forces, and provide a soft potential for dark energy. We further argue that these models can explain leptogenesis naturally through the decays of the right-handed neutrinos.