Physical, numerical, and computational challenges of modeling neutrino transport in core-collapse supernovae
Physical, numerical, and computational challenges of modeling neutrino transport in core-collapse supernovae
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DOI：
10.1007/s41115-020-00010-8
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发表时间：
2020-10
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影响因子：
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通讯作者：
A. Mezzacappa;E. Endeve;O. E. Bronson Messer;S. Bruenn
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作者：
A. Mezzacappa;E. Endeve;O. E. Bronson Messer;S. Bruenn
在Colgate和白色的开创性论文发表50多年后，核心坍缩超新星是中微子驱动的这一提议仍然是积极研究的主题。威尔逊提出了这一范式的现代版本，认为超新星激波是由中微子加热提供动力的，而中微子加热是通过吸收从原中子星星表面或中微子层发射的电子味中微子和反中微子来调节的。中微子与恒星核心流体的弱相互作用，其理论仍在发展中，是风味和能量依赖。伴随的中微子平均自由程延伸了许多数量级，并且相对于恒星核心半径来说永远不会很小。因此，中微子从来都不是流体状的。相反，我们需要用分布函数来描述它们的动力学，这些分布函数决定了中微子在六维相空间中的位置、方向和能量的数密度，或者用中微子分布的角动量来描述它们，这些角动量提供了中微子在四维相空间子空间中的位置和能量的数密度。反过来，计算挑战是双重的：（i）将控制这些分布或力矩演化的动力学方程映射到离散表示上，这些离散表示是稳定的，准确的，也许最重要的是，尊重物理定律，如轻子数和能量守恒以及中微子的费米-狄拉克性质;（ii）开发有效的，超级计算机体系结构意识的解决方法，所得的非线性代数方程。在这篇评论中，我们提出了目前的最先进的尝试，以满足这一挑战。
The proposal that core collapse supernovae are neutrino driven is still the subject of active investigation more than 50 years after the seminal paper by Colgate and White. The modern version of this paradigm, which we owe to Wilson, proposes that the supernova shock wave is powered by neutrino heating, mediated by the absorption of electron-flavor neutrinos and antineutrinos emanating from the proto-neutron star surface, or neutrinosphere. Neutrino weak interactions with the stellar core fluid, the theory of which is still evolving, are flavor and energy dependent. The associated neutrino mean free paths extend over many orders of magnitude and are never always small relative to the stellar core radius. Thus, neutrinos are never always fluid like. Instead, a kinetic description of them in terms of distribution functions that determine the number density of neutrinos in the six-dimensional phase space of position, direction, and energy, for both neutrinos and antineutrinos of each flavor, or in terms of angular moments of these neutrino distributions that instead provide neutrino number densities in the four-dimensional phase-space subspace of position and energy, is needed. In turn, the computational challenge is twofold: (i) to map the kinetic equations governing the evolution of these distributions or moments onto discrete representations that are stable, accurate, and, perhaps most important, respect physical laws such as conservation of lepton number and energy and the Fermi–Dirac nature of neutrinos and (ii) to develop efficient, supercomputer-architecture-aware solution methods for the resultant nonlinear algebraic equations. In this review, we present the current state of the art in attempts to meet this challenge.