Bhatnagar-Gross-Krook subgrid model for neutrino quantum kinetics

Journal Article · 08 April 2024 · Physical Review. D.

DOI: https://doi.org/10.1103/physrevd.109.083013 · OSTI ID:2467383

Nagakura, Hiroki  ^[1]; Johns, Lucas  ^[2]; Zaizen, Masamichi  ^[3]

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1. National Astronomical Observatory of Japan, Tokyo (Japan)
2. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
3. Waseda Univ., Shinjuku (Japan)

Here, we present a new subgrid model for neutrino quantum kinetics, which is primarily designed to incorporate effects of collective neutrino oscillations into neutrino-radiation-hydrodynamic simulations for core-collapse supernovae and mergers of compact objects. We approximate the neutrino oscillation term in a quantum kinetic equation using the Bhatnagar-Gross-Krook (BGK) relaxation-time prescription, and the transport equation is directly applicable for classical neutrino transport schemes. The BGK model is motivated by recent theoretical indications that nonlinear phases of collective neutrino oscillations settle into quasisteady structures. We explicitly provide basic equations of the BGK subgrid model for both multiangle and moment-based neutrino transport to facilitate the implementation of the subgrid model in the existing neutrino transport schemes. We also show the capability of our BGK subgrid model by comparing it to fully quantum kinetic simulations for fast neutrino-flavor conversion. We find that the overall properties can be well reproduced in the subgrid model; the error of angular-averaged survival probability of neutrinos is within ~20%. By identifying the source of error, we also discuss perspectives to improve the accuracy of the subgrid model.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE; USDOE Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 2467383
• Report Number(s): LA-UR--23-34188
• Journal Information: Physical Review. D., Journal Name: Physical Review. D. Journal Issue: 8 Vol. 109; ISSN 2470-0010
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English