  This paper presents a new technique for developing reduced-order models
(ROMs) for nonlinear radiative transfer problems in high-energy density
physics. The proper orthogonal decomposition (POD) of photon intensities is
applied to obtain global basis functions for the Galerkin projection
(POD-Galerkin) of the time-dependent multigroup Boltzmann transport equation
(BTE) for photons. The POD-Galerkin solution of the BTE is used to determine
the quasidiffusion (Eddington) factors that yield closures for the nonlinear
system of (i) multilevel low-order quasidiffusion (VEF) equations and (ii)
material energy balance equation. Numerical results are presented to
demonstrate accuracy of the ROMs obtained with different low-rank
approximations of intensities.
