Light sterile neutrinos after BICEP-2

The recent discovery of B-modes in the polarization pattern of the Cosmic Microwave Background by the BICEP2 experiment has important implications for neutrino physics.We revisit cosmological bounds on light sterile neutrinos and show that they are compatible with all current cosmological data provided that the mass is relatively low.Using CMB data, including BICEP-2, we find an upper bound of m s 10).However, if the sterile neutrino only partly thermalises it can be compatible with all current data, both cosmological and terrestrial.