论文标题
自我磨练的准平台的特性
Properties of self-gravitating quasi-stationary states
论文作者
论文摘要
最初，通过无碰撞的松弛动力学，准平稳状态（QSS），形成了遥远的平衡自我磨化系统。这些可能是由于结构的自下而上的聚合或自上而下的框架而产生的。它们的准平衡性能通过牛仔裤方程式很好地描述，并且不是通用的，即它们取决于初始条件。为了理解这种依赖性的起源，我们提出了最初冷和球形系统的数值实验的结果，其特征在于初始密度波动的各种选择。这种波动的幅度决定了系统是以自上而下还是自下而上的方式放松。我们发现，所得QSS的统计特性主要取决于编队过程中交换的能量量。特别是，在暴力的自上而下，能量交换很大，QSS显示了一个几乎平坦的密度曲线和Quasi Maxwell-Boltzmann（各向同性）速度分布，而其外部区域的密度分布$ρ（r）\ Propto propto r）\ Propto r^{ - α} $ 0 $ 0 $ 0 $ niman fim the norny em gormed或b. rad或rad或b。我们分析表明，$α= 4 $与数值实验一致。在较不暴力的自下而上动力学中，能量交换要小得多，轨道的细长和$ 0 <α（r）\ le 4 $，其密度曲线非常适合Navarro-frenk-white行为。这种动力学演化均由不均匀的球形隔离系统和从宇宙学模拟中提取的光晕显示出来。我们考虑这些结果与核心-CUSP问题的关系得出的结论是，如果星系通过单片崩溃形成，这是自然解决的。
Initially far out-of-equilibrium self-gravitating systems form, through a collisionless relaxation dynamics, quasi-stationary states (QSS). These may arise from a bottom-up aggregation of structures or in a top-down frame; their quasi-equilibrium properties are well described by the Jeans equation and are not universal, i.e. they depend on initial conditions. To understand the origin of such dependence, we present results of numerical experiments of initially cold and spherical systems characterized by various choices of the spectrum of initial density fluctuations. The amplitude of such fluctuations determines whether the system relaxes in a top-down or a bottom-up manner. We find that statistical properties of the resulting QSS mainly depend upon the amount of energy exchanged during the formation process. In particular, in the violent top-down collapses the energy exchange is large and the QSS show an inner core with an almost flat density profile and a quasi Maxwell-Boltzmann (isotropic) velocity distribution, while their outer regions display a density profile $ρ(r) \propto r^{-α}$ ($α>0$) with radially elongated orbits. We analytically show that $α=4$ in agreement with numerical experiments. In the less violent bottom-up dynamics, the energy exchange is much smaller, the orbits are less elongated and $0< α(r) \le 4$, with a a density profile well fitted by the Navarro-Frenk-White behavior. Such a dynamical evolution is shown by both non-uniform spherical isolated systems and by halos extracted from cosmological simulations. We consider the relation of these results with the core-cusp problem concluding that this is naturally solved if galaxies form through a monolithic collapse.
