Collisional instabilities of neutrinos and their interplay with fast flavor conversion in compact objects

TL;DR

This paper investigates how collisional and fast flavor instabilities of neutrinos interact in dense astrophysical environments like supernovae, revealing that fast oscillations can accelerate collisional instability onset.

Contribution

It provides a numerical analysis of collisional neutrino flavor instabilities, highlighting the impact of asymmetric scattering rates and the interplay with fast flavor conversion.

Findings

Collisional instability is triggered by unequal neutrino and antineutrino scattering rates.

Fast oscillations can hasten the onset of collisional instability.

The study compares neutral-current and charged-current interaction effects.

Abstract

Fast and collisional flavor instabilities possibly occur in the neutrino decoupling regions of core-collapse supernovae and neutron-star mergers. To gain a better understanding of the relevant flavor dynamics, we numerically solve for the collisionally unstable evolution in a homogeneous, anisotropic model. In these calculations collisional instability is precipitated by unequal neutrino and antineutrino scattering rates. We compare the solutions obtained using neutral-current and charged-current interactions. We then study the nonlinear development of fast instabilities subjected to asymmetric scattering rates, finding evidence that the onset of collisional instability is hastened by fast oscillations. We also discuss connections to other recent works on collision-affected fast flavor conversion.