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We present the new code ALCAR developed to model multidimensional, multienergy-group neutrino transport in the context of supernovae and neutron-starmergers. The algorithm solves the evolution equations of the 0th- and 1st-orderangular moments of the specific intensity, supplemented by an algebraicrelation for the 2nd-moment tensor to close the system. The scheme takes intoaccount frame-dependent effects of order O(v/c) as well as the most importanttypes of neutrino interactions. The transport scheme is significantly moreefficient than a multidimensional solver of the Boltzmann equation, while it ismore accurate and consistent than the flux-limited diffusion method. Thefinite-volume discretization of the essentially hyperbolic system of momentequations employs methods well-known from hydrodynamics. For the timeintegration of the potentially stiff moment equations we employ a scheme inwhich only the local source terms are treated implicitly, while the advectionterms are kept explicit, thereby allowing for an efficient computationalparallelization of the algorithm. We investigate various problem setups in oneand two dimensions to verify the implementation and to test the quality of thealgebraic closure scheme. In our most detailed test, we compare a fullydynamic, one-dimensional core-collapse simulation with two publishedcalculations performed with well-known Boltzmann-type neutrino-hydrodynamicscodes and we find very satisfactory agreement.

A new multidimensional, energy-dependent two-moment transport code for neutrino-hydrodynamics