# CAFE-R a code that solves the special relativistic radiation hydrodynamics equations

## TL;DR

This paper introduces CAFE-R, a 3D special-relativistic radiation hydrodynamics code that employs the M1-closure scheme to simulate complex astrophysical phenomena involving radiation and relativistic flows.

## Contribution

The paper presents a novel 3D code using the M1-closure relation for radiation, capable of handling a wide range of optical depths and configurations in relativistic hydrodynamics.

## Key findings

- Successfully tested in 1D and 2D scenarios with various optical depths.
- Demonstrated application to a radiation-driven jet with helical perturbation.
- Code suitable for high-energy astrophysics simulations like GRBs.

## Abstract

We present a 3D special-relativistic radiation hydrodynamics code. It uses the radiative inversion scheme with the M1-closure relation for the radiation equations, which allows the treatment of a wide range of optical depth, temperature and opacity. The radiation field is treated in the grey-body approximation. We present the standard 1D and 2D tests that include both optically thin and thick scenarios, as well as hydrodynamical and radiation pressure dominated configurations. As an application in 3D, we show the evolution of a jet driven by radiation-hydrodynamics with a helical perturbation. The code is expected to allow the exploration of scenarios in high-energy astrophysics where the radiation is important, like sources of GRBs.