# BGK subgrid model for neutrino quantum kinetics Source: [BGK subgrid model for neutrino quantum kinetics]() Collection index: [llms.txt]() Data updated: 2025-10-25T05:54:05.097Z Authors: Hiroki Nagakura, Lucas Johns, Masamichi Zaizen Published: 2023-12-26T19:00:02.000Z ## Abstract 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 quantum kinetic equation by 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 non-linear phases of collective neutrino oscillations settle into quasi-steady structures. We explicitly provide basic equations of the BGK subgrid model for both multi-angle 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 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 $\\sim 20 \\%$. By identifying the source of error, we also discuss perspectives to improve the accuracy of the subgrid model. ## Recorded benchmark results A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage. ## Original sources and implementation [Original paper]() [PDF]()