The cosmic neutrino background

The cosmic neutrino background is expected to consist of relic neutrinos from the Big Bang, of neutrinos produced during nuclear burning in stars, of neutrinos released by gravitational stellar collapse and of neutrinos produced by cosmic ray interactions with matter and radiation in the interstellar and intergalactic medium. Formation of baryonic dark matter in the early Universe, matter‐antimatter annihilation in a baryonic symmetric Universe and dark matter annihilation could have contributed significantly to the cosmic neutrino background. The purpose of this paper is to review the properties of these cosmic neutrino backgrounds, the indirect evidence for their existence and the prospects for their detection in view of the dramatic progress in neutrino physics and astronomy that took place last year.