Relaxed big bang nucleosynthesis constraints on neutrino oscillation parameters

We study the cosmological constraints on active-sterile neutrino oscillations nu(e) <-> nu(s) for the case when nu(s) is partially filled initially, i.e. 0 < delta N-s < 1. We provide numerical analysis of the cosmological production of He-4, in the presence of nu(e) <-> nu(s) oscillations, effective after neutrino decoupling, accounting for all known oscillations effects on cosmological nucleosynthesis. Cosmological constraints on oscillation parameters corresponding to higher than 5% He-4 overproduction and different non-zero initial populations of the sterile state delta N-s < 1 are calculated. These generalized cosmological constraints corresponding to delta N-s > 0 are relaxed in comparison with the delta N-s = 0 case and the relaxation is proportional to dNs.