Gmunu中的广义相对论辐射输运方案 I：基于双矩的多频率辐射输运实现与代码测试
General-relativistic radiation transport scheme in $\texttt{Gmunu}$ I: Implementation of two-moment based multi-frequency radiative transfer and code tests
AI总结：
本文在Gmunu代码中实现了基于双矩的广义相对论多群辐射输运模块，采用有限体积离散和隐式-显式龙格-库塔时间积分，并通过数值基准测试及中子星和超新星建模验证了其有效性。
摘要：
我们介绍了在广义相对论多重网格数值代码（Gmunu）中基于双矩的广义相对论多群辐射输运模块的实现。在求解广义相对论磁流体力学和采用共形平坦近似的爱因斯坦方程的基础上，该代码求解辐射的零阶矩和一阶矩的演化方程。采用解析闭合关系来获得高阶矩并封闭方程组。辐射矩采用有限体积离散化。空间和频率空间中的平流项采用显式处理。此外，在光学厚区域非常刚性的辐射-物质相互作用项采用隐式求解。时间积分采用隐式-显式龙格-库塔格式。我们通过从频率积分到频率依赖情形的一系列数值基准测试来检验该实现。此外，我们还展示了其在热中子星和核心坍缩超新星建模中的天体物理应用，并与其他中微子输运代码进行了比较。
英文摘要：
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.
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