Time-dependent, quasi-steady, and global features of fast neutrino-flavor conversion

Hiroki Nagakura, Masamichi Zaizen

Published 2022-06-08Version 1

Despite the theoretical indication that fast neutrino-flavor conversion (FFC) ubiquitously occurs in core-collapse supernova and binary neutron star merger, the lack of global simulations has been the greatest obstacle to study their astrophysical consequences. In this Letter, we present the first global simulation of FFC in spherical symmetry by using a novel approach, in which the injected number of neutrinos into simulation box is systematically changed, and then we explore general characteristics of FFC in global scale. We find that FFC in all models achieves quasi-steady state in the non-linear regime, and its saturation property of FFC is universal. We also find that temporal- and spatial variations of FFC are smeared out at large radii due to phase cancellation through neutrino self-interactions. Finally, we provide a new diagnostic quantity, ELN-XLN angular crossing, to assess the non-linear saturation of FFC.