Multi-Frequency General Relativistic Radiation-Hydrodynamics with $bf{M}_1$ Closure. (arXiv:2007.12195v1 [astro-ph.IM])
<a href="http://arxiv.org/find/astro-ph/1/au:+Anninos_P/0/1/0/all/0/1">Peter Anninos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fragile_P/0/1/0/all/0/1">P. Chris Fragile</a>

We report on recent upgrades to our general relativistic
radiation-magnetohydrodynamics code, Cosmos++, which expands the two-moment,
$bf{M}_1$, radiation treatment from grey to multi-frequency transport,
including Doppler and gravitational frequency shifts. The solver accommodates
either photon (Bose-Einstein) or neutrino (Fermi-Dirac) statistical
distribution functions with absorption, emission, and elastic scattering
processes. An implicit scheme is implemented to simultaneously solve the
primitive inversion problem together with the radiation-matter coupling source
terms, providing stability over a broad range of opacities and optical depths
where the interactions terms can be stiff. We discuss our formulations and
numerical methods, and validate our methods against a wide variety of test
problems spanning optically thin to thick regimes in flat, weakly curved, and
strongly curved spacetimes.

We report on recent upgrades to our general relativistic
radiation-magnetohydrodynamics code, Cosmos++, which expands the two-moment,
$bf{M}_1$, radiation treatment from grey to multi-frequency transport,
including Doppler and gravitational frequency shifts. The solver accommodates
either photon (Bose-Einstein) or neutrino (Fermi-Dirac) statistical
distribution functions with absorption, emission, and elastic scattering
processes. An implicit scheme is implemented to simultaneously solve the
primitive inversion problem together with the radiation-matter coupling source
terms, providing stability over a broad range of opacities and optical depths
where the interactions terms can be stiff. We discuss our formulations and
numerical methods, and validate our methods against a wide variety of test
problems spanning optically thin to thick regimes in flat, weakly curved, and
strongly curved spacetimes.

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