Neutrinos, their partners, and unification

Efforts to unify group-theoretically the standard-model gauge interactions with the generation structure of fermions and their mirror partners should be accompanied by the unification of the corresponding gauge couplings. In this paper, the possibility of such a unification is studied, and conclusio ns on possible symmetry-breaking channels and scales as well as on the ferm ion content of the theory are drawn. The breaking of some of the symmetries allows various Majorana masses for neutrinos and their mirror partners, so these are studied next. Implications for neutrino mixings and mass hierarc hies in connection with recent experimental results. as well as for electro weak precision tests, are then discussed.