"Multiangle treatment is essential to accurately capture FFC effects... approximate truncated moment methods may overlook or falsely identify FFC signals."
Waseda University | May 2026
A research team led by Assistant Professor/Junior Researcher Ryuichiro Akaho from Waseda University, Japan, with co-authors Dr. Hiroki Nagakura from the National Astronomical Observatory of Japan and Professor Shoichi Yamada from Waseda University, has conducted core-collapse supernova (CCSN) simulations that include multiangle neutrino transport to study the effects of fast flavor conversion (FFC). The study was published online on May 11, 2026, and in Physical Review Letters Volume 136, Issue 19 on May 15, 2026.
Methods
The team combined a quantum kinetic theory-based FFC model with multidimensional Boltzmann neutrino radiation hydrodynamics simulations. They identified where FFC occurs using neutrino angular distributions calculated during the simulation itself. The FFC subgrid model uses the Bhatnagar-Gross-Krook relaxation scheme to determine neutrino flavor states.
Results
- Bifurcated impact: FFC promotes shock revival and boosts explosion energy for the lowest-mass progenitor (9 solar masses) but inhibits explosion for higher-mass progenitors (12, 16, 20 solar masses).
- Mechanism: The mass accretion rate determines the effect. For high mass accretion rates, FFC reduces neutrino luminosity and yields negative net heating; for low mass accretion rates, heating efficiency enhancement outweighs luminosity reduction, giving positive net heating.
- Simulations: Included successful and failed explosions, models with zero-age main sequence masses of 9, 12, 16, and 20 solar masses, and three nuclear equations of state (Furusawa-Togashi, Dirac-Brückner-Hartree-Fock, chiral effective field theory).
Significance
The authors argue that multiangle treatment is essential to accurately capture FFC effects, and that approximate truncated moment methods may overlook or falsely identify FFC signals.