Damping of self-induced neutrino flavor transitions due to inhomogeneities

Abstract

Self-induced neutrino flavor dynamics has been typically characterized assuming that either the time (in the core-collapse supernova environment) or space (in the early universe) homogeneity in the initial conditions is preserved through the evolution. In this talk we show that small deviations from an initial postulated homogeneity can be amplified by the interacting neutrino gas, leading to a new flavor instability. To this end, we consider a simple two flavor isotropic neutrino gas evolving in time, and initially composed by only νe and ν‾e with equal densities. In the homogeneous case, this system shows a bimodal instability in the inverted mass hierarchy scheme, leading to the well studied flavor pendulum behavior. To break space homogeneity, we introduce small amplitude space-dependent perturbations in the matter potential. We find that even for arbitrarily tiny inhomogeneities, the system evolution runs away from the stable pendulum behavior and the space-averaged ensemble evolves towards flavor equilibrium.