Closure in flux-limited neutrino diffusion and two-moment transport

Two-dimensional maximum entropy closure and various standard one-dimensional closures in flux-limited neutrino diffusion and two-moment transport are compared against direct numerical solutions of the neutrino Boltzmann equation. The approximate transport based on particular closures of the moment equations is rated by testing so-called weak equivalence of the first three moments of the neutrino radiation field. Additionally we consider strong equivalence of the maximum entropy angular model distribution. Our calculations are performed on two different matter backgrounds and involve several neutrino energies. As an alternative multiple energy test we look at the behavior of spectral and energy-averaged Eddington factors. Among the closures considered, two-dimensional maximum entropy closure is found to overall approximate most closely the full transport solutions.