Levin Yan, Pakter Renato, Rizzato Felipe B
Instituto de Física, UFRGS, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS, Brazil.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Aug;78(2 Pt 1):021130. doi: 10.1103/PhysRevE.78.021130. Epub 2008 Aug 21.
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 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 tauG-N , collisionless relaxation leads to a gravothermal collapse.
理论和模拟被用于研究引力N体系统的无碰撞弛豫。结果表明，当初始单粒子分布函数满足维里条件——势能为动能的负两倍时，系统会迅速弛豫到一种亚稳态，该亚稳态由带截止的林登 - 贝尔分布定量描述。如果初始分布函数不满足维里要求，系统会经历剧烈振荡，导致部分质量蒸发。剩余粒子相分离成核 - 晕结构。所提出的理论使我们能够在没有任何可调参数的情况下，定量预测中心核中剩余质量的数量和分布。在更长的时间尺度τG - N上，无碰撞弛豫会导致引力热坍缩。
