arXiv 2109.043972021-09astro-ph.CO

无耗散宇宙学模拟中功率谱的精度

Accuracy of power spectra in dissipationless cosmological simulations

Sara Maleubre, Daniel Eisenstein, Lehman H. Garrison, Michael Joyce

备注：: 14 pages, 10 figures, version to match published version. Additional subsection in Shot noise and discreteness effects
发表信息：: MNRAS (2022), 512, 1829-1842
DOI：: 10.1093/mnras/stac578

摘要：

我们利用一套大的\emph{N}体模拟（N= $4096^3$）与\Abacus，无标度模型与一系列的频谱指数$n$，以更好地理解和量化收敛的物质功率谱。使用自相似性，以确定收敛区域，我们表明，在给定的精度水平解决的最大波数作为时间的函数单调增加。在1\%的水平，它开始在早期的一小部分$k_Λ$，初始网格的奈奎斯特波数，并达到最多，如果力软化足够小，$\sim 2-3 k_Λ$在我们发展到最后的时间。在$5\%$级别，精度在后期扩展到$5k_Λ$阶的波数。表达为比例因子的适当函数，精度显示出非常简单的$n$依赖性，允许外推以将保守边界置于非无标度模型（如LCDM）的\emph{N} -体模拟精度上。我们注意到，由于收敛范围中的离散化而产生的偏差并不能很好地用散粒噪声建模，减去它实际上会降低准确度。我们的研究结果与最近使用大型宇宙学模拟（例如Euclid Flagship）旨在约束轻度非线性制度的研究所采用的关于分辨率的保守假设大致一致。另一方面，我们注意到，结论小规模集群（例如，关于稳定的聚类的有效性）使用PS数据在波数大于几个$k_Λ$可能需要修改我们的收敛分析。

英文摘要：

We exploit a suite of large \emph{N}-body simulations (up to N=$4096^3$) performed with \Abacus, of scale-free models with a range of spectral indices $n$, to better understand and quantify convergence of the matter power spectrum. Using self-similarity to identify converged regions, we show that the maximal wavenumber resolved at a given level of accuracy increases monotonically as a function of time. At the 1\% level it starts at early times from a fraction of $k_Λ$, the Nyquist wavenumber of the initial grid, and reaches at most, if the force softening is sufficiently small, $\sim 2-3 k_Λ$ at the very latest times we evolve to. At the $5\%$ level, accuracy extends up to wavenumbers of order $5k_Λ$ at late times. Expressed as a suitable function of the scale-factor, accuracy shows a very simple $n$-dependence, allowing a extrapolation to place conservative bounds on the accuracy of \emph{N}-body simulations of non-scale free models like LCDM. We note that deviations due to discretization in the converged range are not well modelled by shot noise, and subtracting it in fact degrades accuracy. Quantitatively our findings are broadly in line with the conservative assumptions about resolution adopted by recent studies using large cosmological simulations (e.g. Euclid Flagship) aiming to constrain the mildly non-linear regime. On the other hand, we remark that conclusions about small scale clustering (e.g. concerning the validity of stable clustering) obtained using PS data at wavenumbers larger than a few $k_Λ$ may need revision in light of our convergence analysis.

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