New results in the physics of neutrino oscillations

I report on recent theoretical results about neutrino mixing and oscillations. I show that in Quantum Field Theory, mixing transformations are not trivial and the vacuum for the mixed fields has a condensate structure. This fact has phenomenological consequences on neutrino oscillations: the oscillation formula turns out to have an additional oscillating piece and energy dependent amplitudes. The usual Pontecorvo formula is recovered in the relativistic limit. I report also about preliminary results on the presence of a topological (Berry) phase for oscillating neutrinos.