Neutrino Flavor Evolution in High Flux Astrophysical Environments

TL;DR

This paper investigates neutrino flavor evolution in high-flux astrophysical environments, incorporating complex interactions and non-forward scattering, revealing rapid equilibration processes that influence astrophysical phenomena and neutrino observations.

Contribution

It introduces a semi-classical approach to neutrino evolution that includes non-forward scattering and many-body effects, advancing understanding of flavor dynamics in extreme astrophysical settings.

Findings

Rapid flavor and energy equilibration among neutrinos and antineutrinos.

Standard MSW oscillations emerge as a limit of the complex evolution.

Neutrino interactions significantly affect nucleosynthesis and energy deposition.

Abstract

We examine neutrino evolution in astrophysical environments where the neutrino flux is very large, including core-collapse supernovae and neutron star mergers. In these environments, the neutrino-neutrino and neutrino-antineutrino interactions are crucial. We include non-forward scattering of neutrinos and anti-neutrinos in a semi-classical treatment. Because of the large scale of neutrino momenta (2-10 MeV), the quantum evolution problem can be treated as a sum over incoherent paths in the and flavor of each neutrino. The phases between different neutrinos are essentially random because of the large kinetic terms. Momentum is conserved at each vertex, and important flavor symmetries are retained. Dynamics in the many-body neutrino system enable rapid equilibration in the energy and angular distributions of all flavors, and an equilibration of products of neutrino and anti-neutrino densities for each flavor at either large or zero background matter density. We also describe the evolution at moderate densities where the mass eigenstates differ for neutrinos and antineutrinos, and with time-varying background matter densities. The evolution maintains relevant symmetries and reduces to standard MSW oscillations in the appropriate limits. The rapid equilibration in energy and flavor can significantly impact energy deposition and nucleosynthesis in high-flux astrophysical environments, and potentially flavor energy relations in terrestrial supernovae neutrino observations.