引力系统中的无碰撞弛豫：从剧烈弛豫到引力热坍缩
Collisionless relaxation in gravitational systems: From violent relaxation to gravothermal collapse
摘要：
利用理论和模拟方法研究了引力$N$ -物体系统的无碰撞弛豫过程。结果表明，当初始单粒子分布函数满足维里条件（势能为动能的负2倍）时，系统迅速弛豫到一个亚稳态，该亚稳态由具有截止值的Lynden-Bell分布{ \it定量描述}.如果初始分布函数不满足维里要求，系统会发生剧烈振荡，导致质量部分蒸发。剩余的颗粒相分离成核-晕结构。提出的理论使我们能够定量地预测留在中央核心的质量的数量和分布，没有任何可调参数。在较长的时间尺度上，$τ_G \sim N$无碰撞弛豫导致重力热塌缩。
英文摘要：
Theory and simulations are used to study collisionless relaxation of a gravitational $N$-body system. It is shown that when the initial one particle distribution function satisfies the virial condition -- potential energy is minus twice the kinetic energy -- the system quickly relaxes to a metastable state described {\it quantitatively} by the Lynden-Bell distribution with a cutoff. If the initial distribution function does not meet the virial requirement, the system undergoes violent oscillations, resulting in a partial evaporation of mass. The leftover particles phase separate into a core-halo structure. The theory presented allows us to quantitatively predict the amount and the distribution of mass left in the central core, without any adjustable parameters. On a longer time scale $τ_G \sim N$ collisionless relaxation leads to a gravothermal collapse.
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