Three-Dimensional Boltzmann-Hydro Code for core-collapse in massive stars III. A New method for momentum feedback from neutrino to matter. (arXiv:1906.10143v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Nagakura_H/0/1/0/all/0/1">Hiroki Nagakura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sumiyoshi_K/0/1/0/all/0/1">Kohsuke Sumiyoshi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yamada_S/0/1/0/all/0/1">Shoichi Yamada</a>

We present a new method for neutrino-matter coupling in multi-dimensional
radiation-hydrodynamic simulations of core-collapse supernova (CCSN) with the
full Boltzmann neutrino transport. The development is motivated by the fact
that the accurate conservation of momentum is required for reliable numerical
modelings of CCSN dynamics including a recoil of proto-neutron star (PNS). The
new method is built on a hybrid approach, in which we use the energy-momentum
tensor of neutrinos to compute the momentum feedback from neutrino to matter in
the optically thick region while we employ the collision term in the optically
thin region. In this method we utilize a general relativistic description of
radiation-hydrodynamics with angular moments, which allows us to evaluate the
momentum feedback from neutrino to matter without inconsistency with our
Boltzmann solver. We demonstrate that the new method substantially improves the
accuracy of linear momentum conservation in our CCSN simulations under
reasonable angular resolutions in momentum space, alleviating the difficulty in
giving the diffusion limit precisely with the discrete ordinate (Sn) method. It
is the first-ever demonstration that the PNS kick can be handled directly and
properly in multi-dimensional radiation-hydrodynamic simulations with the full
Boltzmann neutrino transport.

We present a new method for neutrino-matter coupling in multi-dimensional
radiation-hydrodynamic simulations of core-collapse supernova (CCSN) with the
full Boltzmann neutrino transport. The development is motivated by the fact
that the accurate conservation of momentum is required for reliable numerical
modelings of CCSN dynamics including a recoil of proto-neutron star (PNS). The
new method is built on a hybrid approach, in which we use the energy-momentum
tensor of neutrinos to compute the momentum feedback from neutrino to matter in
the optically thick region while we employ the collision term in the optically
thin region. In this method we utilize a general relativistic description of
radiation-hydrodynamics with angular moments, which allows us to evaluate the
momentum feedback from neutrino to matter without inconsistency with our
Boltzmann solver. We demonstrate that the new method substantially improves the
accuracy of linear momentum conservation in our CCSN simulations under
reasonable angular resolutions in momentum space, alleviating the difficulty in
giving the diffusion limit precisely with the discrete ordinate (Sn) method. It
is the first-ever demonstration that the PNS kick can be handled directly and
properly in multi-dimensional radiation-hydrodynamic simulations with the full
Boltzmann neutrino transport.

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