Can we ignore the time dependence in matter neutrino resonance?

TL;DR

This paper investigates matter neutrino resonance near neutron star mergers, revealing that steady-state assumptions are invalid and that time-dependent models are essential for accurate neutrino flavor evolution predictions.

Contribution

It demonstrates that time-independent models produce unstable solutions, emphasizing the importance of time-dependent simulations in understanding neutrino flavor dynamics in dense astrophysical environments.

Findings

Time-independent models yield unstable steady states.

Time-dependent simulations show different flavor evolution.

Steady-state assumptions are generally invalid for MNR.

Abstract

In the vicinity of neutron star mergers (NSMs), it is possible for the neutrino self-interaction potential to cancel with the matter potential leading to matter neutrino resonance (MNR). MNR is one of the most interesting mechanisms by which neutrino flavor evolution can occur in dense astrophysical environments. Previous studies have typically assumed that the neutrino flavor field evolves to a steady state -- a simplification also used in other self-interaction models such as the neutrino-bulb model. Here, we perform reproducible calculations of MNR using both time-independent and time-dependent formalisms and show that they yield qualitatively different flavor survival probabilities. The time-independent approach produces unstable steady-state solutions that differ fundamentally from the dynamical behavior captured in time-dependent simulations. These results demonstrate that the steady-state assumption is generally invalid, and physical interpretations based on time-independent calculations of dense neutrino systems require re-evaluation.