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Free keywords:
Astrophysics, Instrumentation and Methods for Astrophysics, astro-ph.IM, Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
Abstract:
We present the implementation of two-moment based general-relativistic
multi-group radiation transport module in the $\texttt{G}$eneral-relativistic
$\texttt{mu}$ltigrid $\texttt{nu}$merical ($\texttt{Gmunu}$) code. On top of
solving the general-relativistic magnetohydrodynamics and the Einstein
equations with conformally flat approximations, the code solves the evolution
equations of the zeroth- and first-order moments of the radiations. Analytic
closure relation is used to obtain the higher order moments and close the
system. The finite-volume discretisation has been adopted for the radiation
moments. The advection in spatial and frequency spaces are handled explicitly.
In addition, the radiation-matter interaction terms, which are very stiff in
the optically thick region, are solved implicitly. Implicit-explicit
Runge-Kutta schemes are adopted for time integration. We test the
implementation with a number of numerical benchmarks from frequency-integrated
to frequency dependent cases. Furthermore, we also illustrate the astrophysical
applications in hot neutron star and core-collapse supernovae modellings, and
compare with other neutrino transport codes.
