PREPRINT
1B3188F4-4E20-4818-BFC1-C13DF642899B

# Neutrino Flavor Conversion, Advection, and Collisions: The Full Solution

Shashank Shalgar, Irene Tamborra
arXiv:2207.04058

Submitted on 8 July 2022

## Abstract

At high densities in compact astrophysical sources, the coherent forward scattering of neutrinos onto each other is responsible for making the flavor evolution non-linear. Under the assumption of spherical symmetry, we present the first simulations tracking flavor transformation in the presence of neutrino-neutrino forward scattering, neutral and charged current collisions with the matter background, as well as neutrino advection. We find that, although flavor equipartition could be one of the solutions, it is not a generic outcome, as often postulated in the literature. Intriguingly, the strong interplay between flavor conversion, collisions, and advection leads to a spread of flavor conversion across the neutrino angular distributions and neighboring spatial regions. Our simulations show that slow and fast flavor transformations occur simultaneously. In the light of this, looking for crossings in the electron neutrino lepton number as a diagnostic tool of the occurrence of flavor transformation in the high-density regime is a limiting method.

## Preprint

Comment: 12 pages, 7 figures. Revtex4-1, 2-column format

Subjects: Astrophysics - High Energy Astrophysical Phenomena; High Energy Physics - Phenomenology