Amplification of Isocurvature Perturbations induced by Active-Sterile Neutrino Oscillations

TL;DR

This paper explores how active-sterile neutrino oscillations in the early universe can amplify isocurvature perturbations, leading to the formation of lepton domains with potential super-horizon sizes, influenced by baryon inhomogeneities.

Contribution

It introduces a mechanism linking neutrino oscillations and baryon inhomogeneities to the formation of large-scale lepton domains in the early universe.

Findings

Lepton domains can form due to active-sterile neutrino oscillations.

Lepton domain sizes can be larger than the horizon.

The structure of domains reflects baryon inhomogeneity spectra.

Abstract

We show how the generation of a lepton number in the Early Universe induced by active-sterile neutrino oscillations, in presence of small baryon number inhomogeneities, gives rise to the formation of lepton domains, regions with different values of active neutrino chemical potential. The structure of these domains reflects the spectral features of the baryon number inhomogeneities that generated it. An interesting aspect of the mechanism is that the size of lepton domains can be super-horizon.