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arXiv 2409.17232hep-phastro-ph.HE
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中微子快速味演化理论。第二部分:不稳定性边缘的解

Theory of neutrino fast flavor evolution. Part II. Solutions at the edge of instability

Damiano F. G. Fiorillo, Georg G. Raffelt

AI总结:

针对致密中微子环境中的快速集体味转换,本文利用色散关系的小增长率展开分析弱不稳定模式,导出增长率与不稳定波数范围的显式表达式。

摘要:

在致密中微子环境中,例如核心坍缩超新星或中子星并合所提供的环境,中微子的角分布可能对集体味转换不稳定,而其结果仍有待充分理解。这些转换比流体动力学尺度快得多,这表明自洽构型可能永远不会处于强不稳定状态。基于这一动机,我们研究弱不稳定模式,即增长率较小的模式。我们证明,我们新建立的色散关系(本系列论文的 Paper I)允许按小增长率的幂次展开。对于弱不稳定分布,我们证明不稳定模式要么必须以亚光速相速度运动,要么非常接近光速。这种不稳定性由与波发生共振运动的中微子提供能量,从而使我们能够导出增长率的显式表达式。对于文献中通常假设的轴对称分布,数值算例展示了这些表达式的准确性。我们还指出,对于经常研究的一维系统,不应忘记破坏轴对称性的模式,并且我们给出了表现出不稳定性的波数范围的显式表达式。

英文摘要:

In dense neutrino environments, such as provided by core-collapse supernovae or neutron-star mergers, neutrino angular distributions may be unstable to collective flavor conversions, whose outcome remains to be fully understood. These conversions are much faster than hydrodynamical scales, suggesting that self-consistent configurations may never be strongly unstable. With this motivation in mind, we study weakly unstable modes, i.e., those with small growth rates. We show that our newly developed dispersion relation (Paper~I of this series) allows for an expansion in powers of the small growth rate. For weakly unstable distributions, we show that the unstable modes must either move with subluminal phase velocity, or very close to the speed of light. The instability is fed from neutrinos moving resonantly with the waves, allowing us to derive explicit expressions for the growth rate. For axisymmetric distributions, often assumed in the literature, numerical examples show the accuracy of these expressions. We also note that for the often-studied one-dimensional systems one should not forget the axial-symmetry-breaking modes, and we provide explicit expressions for the range of wavenumbers that exhibit instabilities.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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