Time-dependent, quasi-steady, and global features of fast neutrino-flavor conversion. (arXiv:2206.04097v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Nagakura_H/0/1/0/all/0/1">Hiroki Nagakura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zaizen_M/0/1/0/all/0/1">Masamichi Zaizen</a>

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.

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.

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