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arXiv 1403.4476astro-ph.HE
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核塌缩超新星中微子输运的多维特征

Multi-dimensional Features of Neutrino Transfer in Core-Collapse Supernovae

K. Sumiyoshi, T. Takiwaki, H. Matsufuru, S. Yamada

摘要:

通过求解中微子分布函数的玻尔兹曼方程,研究了超新星核内中微子转移的多维性质。采用具有代表性的快照后反弹核心从其他超新星模拟在三维空间中,我们解决了时间演化的中微子分布函数的定态的玻尔兹曼求解器。利用S $_n$方法实现的多角度、多能量特性,我们揭示了空间三维中微子输运的真实特征,如非径向通量和非对角爱丁顿张量.此外,我们评估射线的射线近似,关闭我们的代码中的横向运输条款。我们证明了射线-射线近似倾向于沿着每条径向射线传播中微子球周围的量子态的涨落,并且高估了不同径向射线上中微子分布之间的变化。我们发现,射线-射线近似和完全玻尔兹曼输运之间的中微子密度和通量的差异变为~ 20%,这也是局部加热率的情况下,而玻尔兹曼输运中的体积积分加热率被发现只是略大于(~2%)在射线-射线近似中的对应物,由于不同的射线之间的抵消。这些结果表明,我们最好仔细评估各种近似的中微子转移在目前的模拟超新星动力学的可能影响。中微子分布函数的角矩和能量矩的详细信息将有利于未来中微子辐射流体力学数值方法的发展。

英文摘要:

We study the multi-dimensional properties of neutrino transfer inside supernova cores by solving the Boltzmann equations for neutrino distribution functions in genuinely six dimensional (6D) phase space. Adopting representative snapshots of the post-bounce core from other supernova simulations in three dimensions, we solve the temporal evolutions to stationary states of neutrino distribution functions by our Boltzmann solver. Taking advantage of the multi-angle and multi-energy feature realized by the S$_n$ method in our code, we reveal the genuine characteristics of spatially three dimensional (3D) neutrino transfer such as non-radial fluxes and non-diagonal Eddington tensors. In addition, we assess the ray-by-ray approximation, turning off the lateral-transport terms in our code. We demonstrate that the ray-by-ray approximation tends to propagate fluctuations in thermodynamical states around the neutrino-sphere along each radial ray and overestimate the variations between the neutrino distributions on different radial rays. We find that the difference in the densities and fluxes of neutrinos between the ray-by-ray approximation and the full Boltzmann transport becomes ~20%, which is also the case for the local heating rate, whereas the volume-integrated heating rate in the Boltzmann transport is found to be only slightly larger (~2%) than the counterpart in the ray-by-ray approximation due to cancellation among different rays. These results suggest that we had better assess carefully the possible influences of various approximations in the neutrino transfer employed in the current simulations on supernova dynamics. Detailed information on the angle and energy moments of neutrino distribution functions will be profitable for the future development of numerical methods in neutrino-radiation hydrodynamics.

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