Simulations of baryon acoustic oscillations – I. Growth of large-scale density fluctuations
Simulations of baryon acoustic oscillations – I. Growth of large-scale density fluctuations
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重子声振荡的模拟——I.大规模密度涨落的增长
DOI：
10.1111/j.1365-2966.2008.13731.x
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发表时间：
2008
影响因子：
4.8
通讯作者：
Y. Suto
中科院分区：
文献类型：
--
作者：
R. Takahashi;N. Yoshida;T. Matsubara;N. Sugiyama;I. Kayo;T. Nishimichi;Akihito Shirata;A. Taruya;S. Saito;Kazuhiro Yahata;Y. Suto
我们批判性地检验了在宇宙N体模拟中大尺度密度扰动的演变被跟踪得如何。我们首先进行大体积模拟，并在三维傅立叶空间中进行逐模分析。我们发现，大尺度波动的增长明显偏离了线性理论的预测。这些偏差是由于模拟体积的有限性而在最大尺度上与少数几个模式的非线性耦合造成的。然后，我们建立了一个基于二阶微扰理论的解析模型来量化这种影响。我们的模型准确地再现了模拟结果。对于一个单一的实现，二阶效应通常表现为线性理论预测周围的“之”字形图案，它印记了位于真实重子声振荡上的人造“振荡”。虽然多个实现的集合平均值接近线性理论预测，但实现的离散仍然很大，即使对于一侧数百兆秒的大模拟体积。对于标准A冷暗物质模型，对于L=500h-1Mpc的模拟体积和Δk=0.005 h Mpc-1的箱宽，其线性增长率的偏差高达10%，这与高斯随机实现的内禀方差相当。我们发现，只有当我们使用很大体积的L和GPC时，色散尺度为αL-3/2Δk-1/2，平均色散幅度才能小于百分之一。在解释未来使用重子声振荡进行暗能量调查的大规模结构模拟的结果时，需要适当地考虑有限的盒子大小效应。
We critically examine how well the evolution of large-scale density perturbations is followed in cosmological N-body simulations. We first run a large volume simulation and perform a mode-by-mode analysis in three-dimensional Fourier space. We show that the growth of large-scale fluctuations significantly deviates from linear-theory predictions. The deviations are caused by non-linear coupling with a small number of modes at largest scales owing to finiteness of the simulation volume. We then develop an analytic model based on second-order perturbation theory to quantify the effect. Our model accurately reproduces the simulation results. For a single realization, the second-order effect appears typically as 'zig-zag' patterns around the linear-theory prediction, which imprints artificial 'oscillations' that lie on the real baryon acoustic oscillations. Although an ensemble average of a number of realizations approaches the linear-theory prediction, the dispersions of the realizations remain large even for a large simulation volume of several hundred megaparsecs on a side. For the standard A cold dark matter (ACDM) model, the deviations from linear growth rate are as large as 10 per cent for a simulation volume with L = 500 h -1 Mpc and for a bin width in wavenumber of Δk = 0.005 h Mpc -1 , which are comparable to the intrinsic variance of Gaussian random realizations. We find that the dispersions scales as α L -3/2 Δk -1/2 and the mean dispersion amplitude can be made smaller than a per cent only if we use a very large volume of L > 2 h -1 Gpc. The finite box size effect needs to be appropriately taken into account when interpreting results from large-scale structure simulations for future dark energy surveys using baryon acoustic oscillations.