# Neutrino Quantum Kinetics in Compact Objects

## TL;DR

This paper develops a comprehensive quantum kinetic model for neutrino transport in supernovae and neutron star mergers, including all relevant collision processes, and analyzes their effects on neutrino flavor evolution.

## Contribution

It introduces a method to incorporate full neutrino collision terms into quantum kinetic equations and performs the first self-consistent simulation of these effects in relevant astrophysical conditions.

## Key findings

- Electron scattering and nucleon-nucleon bremsstrahlung dominate flavor decoherence in the PNS.
- Absorption processes are most significant near the shock.
- Most collision processes are relevant in the neutrino decoupling region.

## Abstract

Neutrinos play a critical role of transporting energy and changing the lepton density within core-collapse supernovae and neutron star mergers. The quantum kinetic equations (QKEs) combine the effects of neutrino-matter interactions treated in classical Boltzmann transport with the neutrino flavor-changing effects treated in neutrino oscillation calculations. We present a method for extending existing neutrino interaction rates to full QKE source terms for use in numerical calculations. We demonstrate the effects of absorption and emission by nucleons and nuclei, electron scattering, electron-positron pair annihilation, nucleon-nucleon bremsstrahlung, neutrino-neutrino scattering. For the first time, we include all these collision terms self-consistently in a simulation of the full isotropic QKEs in conditions relevant to core-collapse supernovae and neutron star mergers. For our choice of parameters, the long-term evolution of the neutrino distribution function proceeds similarly with and without the oscillation term, though with measurable differences. We demonstrate that electron scattering, nucleon-nucleon bremsstrahlung processes, and four-neutrino processes dominate flavor decoherence in the protoneutron star (PNS), absorption dominates near the shock, and all of the considered processes except elastic nucleon scattering are relevant in the decoupling region. Finally, we propose an effective decoherence opacity that at most energies predicts decoherence rates to within a factor of 10 in our model PNS and within 20% outside of the PNS.