Cosmological unification, dark energy, and the origin of neutrino mass

We suggest that quintessential vacuum energy could be the source of right-handed neutrino masses that feed the seesaw mechanism, which may provide the observed small masses of light standard neutrinos. This idea is naturally implemented in the cosmological unification model based on the global SO(1,1) symmetry, where the early inflation and late-time accelerated expansion of the Universe are driven by the degrees of freedom of a doublet scalar field. In this model, the SO(1,1) custodial symmetry naturally provides the coupling between the Standard Model singlet fermion and quintessence, which sources neutrino masses. We also show that the model predicts a highly suppressed contribution to the relativistic degrees of freedom from quintessential quanta during any late Universe epoch, ensuring the consistency of the model.