Neutrinos in Cosmology

International audienceWe summarize the role of neutrinos in the standard ΛCDM cosmology. Their most important job was to regulate neutron-proton thermal equilibrium in the early Universe, thus setting the initial conditions for primordial nucleosynthesis. More recently, some of them have become non-relativistic, slightly affecting the formation of structures, allowing one to use cosmological measurements to set limits on neutrino masses