Overproduction of primordial helium-4 in the presence of neutrino oscillations

The maximum overproduction of helium-4 in cosmological nucleosynthesis with active–sterile neutrino oscillations, νe↔νs, efficient after decoupling of electron neutrino, is analyzed. The kinetic effects on primordial nucleosynthesis due to neutrino spectrum distortion, caused by oscillations, are precisely taken into account. ximum overproduction of primordial 4He as a function of oscillation parameters is obtained from the self-consistent analysis of the kinetics of the nucleons and the oscillating neutrinos. A maximum relative increase of 4He, up to 13.1% for non-resonant oscillations and up to 31.8% for resonant ones is registered.