Active-Sterile Neutrino Oscillations and Non-Standard Bbn

Active-sterile neutrino oscillations can have remarkable consequences in the early Universe, allowing to draw non standard scenarios for BBN. These are motivated by the necessity of solving claimed discrepancies between standard BBN and the observations both of nuclear abundances and of CMBR anisotropics. Interestingly, one can have scenarios resulting in inhomogeneous primordial nuclear abundances.