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arXiv 2101.02745astro-ph.HEphysics.plasm-ph
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中微子快味不稳定性的粒子模拟

Particle-in-cell Simulation of the Neutrino Fast Flavor Instability

Sherwood Richers, Don E. Willcox, Nicole M. Ford, Andrew Myers

摘要:

中微子驱动着核心坍缩的超新星,从中子星合并的吸积盘中喷出,并决定着这两个系统喷出物中质子和中子的比例,从而在宇宙中产生重元素。不同味道的中微子与物质的相互作用不同,最近的许多工作表明,快速味道不稳定性可能在两个系统中普遍存在,但不稳定性饱和后的最终味道含量尚未得到很好的理解。在这项工作中,我们提出了粒子在细胞的计算,遵循所有口味的中微子和反中微子通过饱和和运动学退相干的演变。我们进行一维的中微子量子动力学的三维模拟,以证明在几个例子的情况下,这种不稳定性的结果。我们展示了轴对称和非对称模式的增长,其波长和增长率与线性稳定性分析的预测相匹配。最后,我们改变中微子和反中微子的数密度,通量大小和通量方向,并证明这些因素修改的增长率和后饱和中微子味丰度。在这些模拟中,弱电子轻子数(ELN)交叉既产生缓慢增长的不稳定性,在初始和最终状态的味道丰度之间的差异很小。在所有这些计算中,相同数量的中微子和反中微子改变了味道,使得它们之间丰度最低的中微子成为饱和后味道变化的限制因素。需要更多的模拟和多维模拟来充分探测初始条件的参数空间。

英文摘要:

Neutrinos drive core-collapse supernovae, launch outflows from neutron star merger accretion disks, and set the ratio of protons to neutrons in ejecta from both systems that generate heavy elements in the universe. Neutrinos of different flavors interact with matter differently, and much recent work has suggested that fast flavor instabilities are likely ubiquitous in both systems, but the final flavor content after the instability saturates has not been well understood. In this work we present particle-in-cell calculations which follow the evolution of all flavors of neutrinos and antineutrinos through saturation and kinematic decoherence. We conduct one-dimensional three-flavor simulations of neutrino quantum kinetics to demonstrate the outcome of this instability in a few example cases. We demonstrate the growth of both axially symmetric and asymmetric modes whose wavelength and growth rate match predictions from linear stability analysis. Finally, we vary the number density, flux magnitude, and flux direction of the neutrinos and antineutrinos and demonstrate that these factors modify both the growth rate and post-saturation neutrino flavor abundances. Weak electron lepton number (ELN) crossings in these simulations produce both slow growth of the instability and little difference between the flavor abundances in the initial and final states. In all of these calculations the same number of neutrinos and antineutrinos change flavor, making the least abundant between them the limiting factor for post-saturation flavor change. Many more simulations and multi-dimensional simulations are needed to fully probe the parameter space of the initial conditions.

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