|
Résumé |
In the primordial Universe, neutrino decoupling occurs only slightly before
electron-positron annihilations. This leads to an increased neutrino energy
density with order 1% spectral distortions compared to the standard
instantaneous decoupling approximation. A precise calculation of neutrino
evolution is needed to assess its consequences on BBN, structure formation or
on the CMB, and requires to take into account multiple effects such as
neutrino oscillations, which represents a genuine numerical challenge.
In this talk, I will review the progress made in the last three decades
towards such an accurate prediction, and present results including for the
first time the full collision term which accounts for neutrino mixing. A
particular focus will be placed on the physical effect of neutrino
oscillations, which allows for an approximate numerical scheme of striking
accuracy. |
