Speaker
Yannis Georis
(Kavli IPMU)
Description
The effective number of neutrinos, Neff, is a key parameter in the standard Lambda-CDM cosmology, which captures how many light degrees of freedom are in the early universe plasma before Big Bang Nucleosynthesis. It is therefore a crucial probe of light and feebly interacting hidden sectors. In this talk, I will review how one can describe the evolution of neutrinos in the early universe using techniques from nonequilibrium quantum field theory. Working in this framework, I will then discuss recent works studying whether higher-order QED corrections can significantly impact the theoretical prediction for Neff in the Standard Model.