  A truncated moment formalism for general relativistic radiation
hydrodynamics, based on the Thorne's moment formalism, is derived. The fluid
rest frame is chosen to be the fiducial frame for defining the radiation
moments. Then, zeroth-, first-, and second-rank radiation moments are defined
from the distribution function with a physically reasonable assumption for it
in the optically thin and thick limits. The source terms are written, focusing
specifically on the neutrino transfer and neglecting higher harmonic angular
dependence of the reaction angle. Finally, basic equations for a truncated
moment formalism for general relativistic radiation hydrodynamics in a closed
covariant form are derived assuming a closure relation among the radiation
stress tensor, energy density, and energy flux, and a variable Eddington
factor, which works well.
