XXth International Conference on Neutrino Physics and Astrophysics

Poster Abstract

S.Pastor (MPI Physik, Munich, Germany)

Neutrino oscillations in dense neutrino media

In the early universe or in some regions of supernovae, the neutrino refractive index is dominated by the neutrinos themselves. Several previous studies have found numerically that these self-interactions have the effect of coupling different neutrino modes in such a way as to synchronize the flavor oscillations which otherwise would depend on the energy of a given mode. We show a simple explanation for this baffling phenomenon in analogy to a system of magnetic dipoles which are coupled by their self-interactions to form one large magnetic dipole which then precesses coherently in a weak external magnetic field. As an application, we study three-flavor neutrino oscillations in the early universe in the presence of neutrino chemical potential. We found that effective flavor equilibrium between all active neutrino species is established well before the big-bang nucleosynthesis epoch if the neutrino oscillation parameters are in the range indicated by the atmospheric neutrino data and by the large mixing angle MSW solution of the solar neutrino problem.

Based on Phys. Rev. D 65 (2002) 053011 and hep-ph/0201287

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