On laboratory-frame radiation hydrodynamics

We derive and discuss the equations of radiation hydrodynamics with all rad iation quantities expressed in the laboratory frame. Relativistically exact transformations from the comoving to laboratory frame are used. We obtain simple, fully covariant, expressions for the radiation energy and momentum source/sink terms using lab-frame radiation quantities. The mathematical si mplicity of having lab-frame radiation quantities in conservative operators on the left-hand side is maintained. The resulting system can be solved ef ficiently using an Eddington tensor formulation for angular dependences, an d an iterative frequency-splitting, in the spirit of the multifrequency-gra y method. Use of lab-frame radiation quantities can present numerical diffi culties in making an accurate connection to the diffusion limit for extreme ly optically thick media; but it may have no difficulty for neutron-transpo rt problems where very large scattering-thicknesses are generally not encou ntered (for non-critical systems). Published by Elsevier Science Ltd.