A faster algorithm for smoothed particle hydrodynamics with radiative transfer in the flux-limited diffusion approximation

We describe a new, faster implicit algorithm for solving the radiation hydrodynamics equations in the flux-limited diffusion approximation for smoothed particle hydrodynamics. This improves on the method elucidated in Whitehouse & Bate by using a Gauss-Seidel iterative method rather than iterating over the exchange of energy between pairs of particles. The new algorithm is typically many thousands of times faster than the old one, which will enable more complex problems to be solved. The new algorithm is tested using the same tests performed by Turner & Stone for ZEUS-2D, and repeated by Whitehouse & Bate.