arXiv 2202.006702022-02-01astro-ph.CO

大质量中微子的高阶初始条件

Higher-order initial conditions with massive neutrinos

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

备注：: 15 pages, 9 figures, with link to software, minor update of version submitted to MNRAS
DOI：: 10.1093/mnras/stac2365

摘要：

中微子有质量的发现对宇宙学有着重要的意义。大质量中微子的主要作用是在小尺度上抑制宇宙结构的生长。这种增长可以用宇宙学的$N$体模拟来精确地模拟，但这样做需要精确的初始条件（IC）。有一个权衡，特别是与一阶集成电路，截断误差晚开始和离散性和相对论性误差早开始之间。通过使用高阶IC在较晚的时间开始仿真，可以最大限度地减少误差。在本文中，我们表明中微子效应可以吸收到高阶拉格朗日微扰理论（LPT）的标度无关系数。这为使用高阶IC进行大规模中微子模拟扫清了道路。我们证明，去高阶大幅提高模拟的准确性。为了与DESI和Euclid等测量的灵敏度相匹配，物质功率谱的误差应该远低于1%。然而，我们发现，一阶Zel'dovich IC导致更大的误差，即使在$z=127$开始，超过1%的$z=0$为$k>0.5\text{ Mpc}^{-1}$的功率谱和$k>0.1\text{ Mpc}^{-1}$的等边双谱在我们的模拟。具有不同中微子质量的功率谱的比率比绝对统计更稳健，但仍然取决于IC的选择。对于考虑的所有统计量，我们在$z=0$获得2LPT和3LPT之间的1%一致性。

英文摘要：

The discovery that neutrinos have mass has important consequences for cosmology. The main effect of massive neutrinos is to suppress the growth of cosmic structure on small scales. Such growth can be accurately modelled using cosmological $N$-body simulations, but doing so requires accurate initial conditions (ICs). There is a trade-off, especially with first-order ICs, between truncation errors for late starts and discreteness and relativistic errors for early starts. Errors can be minimized by starting simulations at late times using higher-order ICs. In this paper, we show that neutrino effects can be absorbed into scale-independent coefficients in higher-order Lagrangian perturbation theory (LPT). This clears the way for the use of higher-order ICs for massive neutrino simulations. We demonstrate that going to higher order substantially improves the accuracy of simulations. To match the sensitivity of surveys like DESI and Euclid, errors in the matter power spectrum should be well below 1%. However, we find that first-order Zel'dovich ICs lead to much larger errors, even when starting as early as $z=127$, exceeding 1% at $z=0$ for $k>0.5\text{ Mpc}^{-1}$ for the power spectrum and $k>0.1\text{ Mpc}^{-1}$ for the equilateral bispectrum in our simulations. Ratios of power spectra with different neutrino masses are more robust than absolute statistics, but still depend on the choice of ICs. For all statistics considered, we obtain 1% agreement between 2LPT and 3LPT at $z=0$.

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