Multi-dimensional features of neutrino transfer in core-collapse supernovae
Multi-dimensional features of neutrino transfer in core-collapse supernovae
复制标题
核心塌陷超新星中微子传输的多维特征
DOI：
10.1088/0067-0049/216/1/5
复制
发表时间：
2015
影响因子：
8.7
通讯作者：
H. Matsufuru and S. Yamada
中科院分区：
文献类型：
--
作者：
K. Sumiyoshi;T. Takiwaki;H. Matsufuru and S. Yamada
我们通过求解真正六维相空间中中微子分布函数的玻尔兹曼方程来研究超新星核心内中微子传输的多维特性。采用来自其他超新星模拟的三维弹跳后核心的代表性快照，我们使用玻尔兹曼求解器求解中微子分布函数到稳态的时间演化。利用我们代码中S n 方法实现的多角度和多能量特征，我们揭示了空间三维中微子传输的真实特征，例如非径向通量和非对角爱丁顿张量。此外，我们评估逐射线近似，关闭代码中的横向传输项。我们证明，逐射线近似倾向于沿着每条径向射线传播中微子球周围热力学状态的波动，并高估了不同径向射线上中微子分布之间的变化。我们发现，逐射线近似和完全玻尔兹曼输运之间的中微子密度和通量差异约为 20%，局部加热速率也是如此，而由于不同射线之间的抵消，玻尔兹曼输运中的体积积分加热速率仅比逐射线近似中的体积积分加热速率稍大（约 2%）。这些结果表明，我们应该仔细评估当前超新星动力学模拟中所采用的中微子转移的各种近似值可能产生的影响。关于中微子分布函数的角度和能量矩的详细信息对于中微子辐射流体动力学数值方法的未来发展将是有益的。
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 phase space. Adopting representative snapshots of the post-bounce core from other supernova simulations in three dimensions, we solve the temporal evolution to stationary states of neutrino distribution functions using 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 neutrino transfer, such as nonradial fluxes and nondiagonal 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 should carefully assess the possible influences of various approximations in the neutrino transfer employed in current simulations of 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.