Title: Sterile Neutrinos and B-L Symmetry,
Abstract: We revisit the relation between the neutrino masses and the spontaneous
breaking of the B-L gauge symmetry. We discuss the main scenarios for Dirac and
Majorana neutrinos and point out two simple mechanisms for neutrino masses. In
this context the neutrino masses can be generated either at tree level or at
quantum level and one predicts the existence of very light sterile neutrinos
with masses below the eV scale. The predictions for lepton number violating
processes such as mu to e and mu to e gamma are discussed in detail. The impact
from the cosmological constraints on the effective number of relativistic
degree of freedom is investigated.