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Astrophysical observations originate from matter that interacts with radiation or transported particles. We develop a pragmatic approximation in order to enable multi-dimensional simulations with basic spectral radiative transfer when the computational resources are not sufficient to solve the complete Boltzmann transport equation. The distribution function of the transported particles is decomposed into trapped and streaming particle components. Their separate evolution equations are coupled by a source term that converts trapped particles into streaming particles. We determine this source term by requiring the correct diffusion limit. For a smooth transition to the free streaming regime, this diffusion source is limited by the matter emissivity. The resulting streaming particle emission rates are integrated over space to obtain the streaming particle flux. A geometric estimate of the flux factor is used to convert the particle flux to the streaming particle density. The efficiency of the scheme results from the freedom to use different approximations for each particle component. In supernovae, reactions with trapped particles on fast time scales establish equilibria that reduce the number of primitive variables required to evolve the trapped particle component. On the other hand, a stationary-state approximation facilitates the treatment of the streaming particle component. Different approximations may apply in applications to stellar atmospheres, star formation, or cosmological radiative transfer. We compare the isotropic diffusion source approximation with Boltzmann neutrino transport of electron flavour neutrinos in spherically symmetric supernova models and find good agreement. An extension of the scheme to the multi-dimensional case is also discussed.
Self-consistent, time-dependent supernova (SN) simulations in three spatial dimensions (3D) are conducted with the Aenus-Alcar code, comparing, for the first time, calculations with fully multi-dimensional (FMD) neutrino transport and the ray-by-ray-
We present multi-dimensional core-collapse supernova simulations using the Isotropic Diffusion Source Approximation (IDSA) for the neutrino transport and a modified potential for general relativity in two different supernova codes: FLASH and ELEPHANT
We derive the event-by-event likelihood that allows to extract the complete information contained in the energy, time and direction of supernova neutrinos, and specify it in the case of SN1987A data. We resolve discrepancies in the previous literatur
Accurate neutrino transport has been built into spherically symmetric simulations of stellar core collapse and postbounce evolution. The results of such simulations agree that spherically symmetric models with standard microphysical input fail to exp
We investigate neutrino-driven convection in core collapse supernovae and its ramifications for the explosion mechanism. We begin with an ``optimistic 15 solar mass precollapse model, which is representative of the class of stars with compact iron co