关于$Λ$ CDM宇宙学模拟中随机性的起始
On the Onset of Stochasticity in $Λ$CDM Cosmological Simulations
摘要：
在$Λ$ CDM宇宙学模拟中，利用一组经典观测量测量了随机性的开始。它被量化为一个给定的可观测值的离散对数的局部导数（在一组不同的模拟中，通过它们的初始实现而略有不同），相对于宇宙增长因子。在欧拉框架下，这里表明，混沌出现在小尺度上，其中动态是非线性的，而它在较大尺度上消失，允许计算对应于~ 3.5 Mpc/h的临界转变尺度。这张照片证实了拉格朗日测量表明，集群内的子结构的分布是部分敏感的初始条件，与临界质量上限缩放大致像扰动的振幅的权力0.15。相应的特征质量，$M_{\rm crit}=2 10^{13} M_{\odot}$，大约是在z=1的非线性临界质量的顺序，并占由暗能量触发加速诱导的去耦。详细的初始条件的敏感性溢出的主机晕（自旋和速度色散张量方向）的整体物理特性，而其他“全球”的属性是相当强大的，并没有表现出混乱（质量，自旋参数，连接和质心位置）。这种明显的差异可能反映了这样一个事实，即对粒子积分的量迅速平均了轨道差异的细节，而其他观测量对形成晕的详细环境更敏感，并反映了表征晕环境的非线性尺度耦合。
英文摘要：
The onset of stochasticity is measured in $Λ$CDM cosmological simulations using a set of classical observables. It is quantified as the local derivative of the logarithm of the dispersion of a given observable (within a set of different simulations differing weakly through their initial realization), with respect to the cosmic growth factor. In an Eulerian framework, it is shown here that chaos appears at small scales, where dynamic is non-linear, while it vanishes at larger scales, allowing the computation of a critical transition scale corresponding to ~ 3.5 Mpc/h. This picture is confirmed by Lagrangian measurements which show that the distribution of substructures within clusters is partially sensitive to initial conditions, with a critical mass upper bound scaling roughly like the perturbation's amplitude to the power 0.15. The corresponding characteristic mass, $M_{\rm crit}=2 10^{13} M_{\odot}$, is roughly of the order of the critical mass of non linearities at z=1 and accounts for the decoupling induced by the dark energy triggered acceleration. The sensitivity to detailed initial conditions spills to some of the overall physical properties of the host halo (spin and velocity dispersion tensor orientation) while other "global" properties are quite robust and show no chaos (mass, spin parameter, connexity and center of mass position). This apparent discrepancy may reflect the fact that quantities which are integrals over particles rapidly average out details of difference in orbits, while the other observables are more sensitive to the detailed environment of forming halos and reflect the non-linear scale coupling characterizing the environments of halos.
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