论文标题
宇宙N体模拟的准确初始条件：最小化截短和离散性错误
Accurate initial conditions for cosmological N-body simulations: Minimizing truncation and discreteness errors
论文作者
论文摘要
宇宙学N体模拟的初始条件下的不准确性很容易成为预测非线性大规模结构的系统误差的最大来源。从理论方面，通常使用拉格朗日扰动理论的位移场的低阶截断来提供初始条件，而第一阶和二阶近似是最常见的。在这里，我们研究了基于三阶拉格朗日扰动理论（3LPT）的初始条件所带来的改进。我们表明，使用3LPT，截断误差被极大地抑制，从而打开门户，以便在Z = 12的迟交中准确地初始化模拟（对于我们考虑的分辨率）。我们分析了扰动截断和粒子离散性对各种汇总统计数据的竞争影响。离散性错误本质上是腐烂的模式，因此在早期初始化时间中得到了强烈的放大。我们表明，使用3LPT的较晚开始提供了最准确的配置，我们发现，在Z = 0时的功率和Biseptrum的连续性流体极限一致，直至我们模拟的粒子nyquist波浪数（K〜3H/MPC）。总之，为了抑制非流体人工制品，我们建议使用3LPT尽可能晚些时候对模拟进行初始化。我们公开提供3列初始条件生成器。
Inaccuracies in the initial conditions for cosmological N-body simulations could easily be the largest source of systematic error in predicting the non-linear large-scale structure. From the theory side, initial conditions are usually provided by using low-order truncations of the displacement field from Lagrangian perturbation theory, with the first and second-order approximations being the most common ones. Here we investigate the improvement brought by using initial conditions based on third-order Lagrangian perturbation theory (3LPT). We show that with 3LPT, truncation errors are vastly suppressed, thereby opening the portal to initializing simulations accurately as late as z=12 (for the resolution we consider). We analyse the competing effects of perturbative truncation and particle discreteness on various summary statistics. Discreteness errors are essentially decaying modes and thus get strongly amplified for earlier initialization times. We show that late starting times with 3LPT provide the most accurate configuration, which we find to coincide with the continuum fluid limit within 1 per cent for the power- and bispectrum at z=0 up to the particle Nyquist wave number of our simulations (k ~ 3h/Mpc). In conclusion, to suppress non-fluid artefacts, we recommend initializing simulations as late as possible with 3LPT. We make our 3LPT initial condition generator publicly available.
