  We present bhlight, a numerical scheme for solving the equations of general
relativistic radiation magnetohydrodynamics (GRRMHD) using a direct Monte Carlo
solution of the frequency-dependent radiative transport equation. bhlight is
designed to evolve black hole accretion flows at intermediate accretion rate,
in the regime between the classical radiatively efficient disk and the
radiatively inefficient accretion flow (RIAF), in which global radiative
effects play a sub-dominant but non-negligible role in disk dynamics. We
describe the governing equations, numerical method, idiosyncrasies of our
implementation, and a suite of test and convergence results. We also describe
example applications to radiative Bondi accretion and to a slowly accreting
Kerr black hole in axisymmetry.
