The isotropic diffusion source approximation for supernova neutrino transport

Liebendörfer, M. and Whitehouse, S. C. and Fischer, T.. (2009) The isotropic diffusion source approximation for supernova neutrino transport. The astrophysical journal. Part 1, Vol. 698. pp. 1174-1190.

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Official URL: http://edoc.unibas.ch/dok/A5253797

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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 multidimensional simulations with basic spectral radiative transfer when the available computational resources are not sufficient to solve the complete Boltzmann transport equation. The distribution function of the transported particles is decomposed into a trapped particle component and a streaming particle component. 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 the evolution of the trapped particle component. 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. Finally, a geometric estimate of the flux factor is used to convert the particle flux to the streaming particle density, which enters the evaluation of streaming particle-matter interactions. The efficiency of the scheme results from the freedom to use different approximations for each particle component. In supernovae, for example, reactions with trapped particles on fast timescales establish equilibria that reduce the number of primitive variables required to evolve the trapped particle component. On the other hand, a stationary-state approximation considerably 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 flavor neutrinos in spherically symmetric supernova models and find good agreement. An extension of the scheme to the multidimensional case is also discussed.
Faculties and Departments:05 Faculty of Science > Departement Physik > Former Organization Units Physics > Astrophysik (Liebendörfer)
UniBasel Contributors:Liebendörfer, Matthias and Whitehouse, Stuart C and Fischer, Tobias
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:University of Chicago Press
Note:Publication type according to Uni Basel Research Database: Journal article
Identification Number:
Last Modified:27 Mar 2014 13:12
Deposited On:22 Mar 2012 13:56

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