arXiv 2010.073212020-10-14astro-ph.CO

模拟遗迹中微子的最佳非线性方法

An optimal nonlinear method for simulating relic neutrinos

Willem Elbers, Carlos S. Frenk, Adrian Jenkins, Baojiu Li, Silvia Pascoli

备注：: 16 pages, 10 figures, submitted to MNRAS
DOI：: 10.1093/mnras/stab2260

摘要：

宇宙学对中微子质量之和提出了最强的电流限制。未来的观测将进一步提高灵敏度，这将需要精确的宇宙学模拟来量化可能的系统不确定性，并对非线性尺度进行预测，其中存在大量信息。然而，中微子热运动产生的散粒噪声限制了模拟的准确性。在本文中，我们介绍了一种新的方法来模拟大尺度结构的形成与中微子，准确地解决了中微子到小尺度，并显着降低了散粒噪声。该方法的工作原理是通过跟踪微扰中微子相空间分布的粒子和减少散粒噪声的功率谱的一个因素$\mathcal{O}\left(10^2\right)$在$z=0$的中微子质量最小，并显着更多的在较高的红移，而不忽略中微子集群所造成的反反应。我们证明，该方法是一个家庭的最佳方法，最大限度地减少散粒噪声的最大偏差的非线性解决方案的一部分。与其他方法相比，我们发现permille级协议的物质功率谱和百分比级协议的大尺度中微子偏置，但在小尺度上的中微子组件的大的差异。该方法的一个基本版本可以很容易地在现有的N体代码中实现，并且可以在显着减少粒子负载的情况下运行中微子模拟。进一步的增益是可能的，通过构建基于微扰理论的背景模型。这种技术的一个主要优点是它适用于所有质量，使整个中微子参数空间的探索一致。

英文摘要：

Cosmology places the strongest current limits on the sum of neutrino masses. Future observations will further improve the sensitivity and this will require accurate cosmological simulations to quantify possible systematic uncertainties and to make predictions for nonlinear scales, where much information resides. However, shot noise arising from neutrino thermal motions limits the accuracy of simulations. In this paper, we introduce a new method for simulating large-scale structure formation with neutrinos that accurately resolves the neutrinos down to small scales and significantly reduces the shot noise. The method works by tracking perturbations to the neutrino phase-space distribution with particles and reduces shot noise in the power spectrum by a factor of $\mathcal{O}\left(10^2\right)$ at $z=0$ for minimal neutrino masses and significantly more at higher redshifts, without neglecting the back-reaction caused by neutrino clustering. We prove that the method is part of a family of optimal methods that minimize shot noise subject to a maximum deviation from the nonlinear solution. Compared to other methods we find permille level agreement in the matter power spectrum and percent level agreement in the large-scale neutrino bias, but large differences in the neutrino component on small scales. A basic version of the method can easily be implemented in existing N-body codes and makes it possible to run neutrino simulations with significantly reduced particle load. Further gains are possible by constructing background models based on perturbation theory. A major advantage of this technique is that it works well for all masses, enabling a consistent exploration of the full neutrino parameter space.

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