The time evolution of fast flavor crossings in post-merger disks around a black hole remnant

Understand

We postprocess a three-dimensional general relativistic, full transport neutrino radiation magnetohydrodynamics simulation of the black hole--accretion disk--wind system thought to be a potential outcome of the GW170817 merger to investigate the presence of electron lepton number (ELN-XLN) crossings in the neutrino angular distribution.

• Neutrinos are evolved with an explicit Monte Carlo method and can interact with matter via emission, absorption, or scattering.
• Within the postprocessing framework, we find ubiquitous occurrence of ELN-XLN crossings at early times ($\sim$ 11ms) but this does not hold for later times in the simulation.
• At postmerger times of $ \sim$ 60 ms and beyond, ELN-XLN crossings are only present near the equator.