Sterile Neutrinos in Big Bang Nucleosynthesis
  We investigate analytically the evolution of the primordial neutrino asymmetry caused by active-sterile neutrino oscillations. In particular, we concentrate on possible chaotic oscillations of the asymmetry. For a certain range of parameters, we find that the asymmetry indeed oscillates, provided we neglect the momentum distribution. 
R.Buras (MPP Munich)