Shapiro Stuart L
Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Phys Rev D. 2018 Jul 15;98(2). doi: 10.1103/physrevd.98.023021. Epub 2018 Jul 31.
We adopt the fluid conduction approximation to study the evolution of spherical star clusters and self-interacting dark matter (SIDM) halos. We also explore the formation and dynamical impact of density cusps that arise in both systems due to the presence of a massive, central black hole. The large N-body, self-gravitating systems we treat are "weakly collisional": the mean free time between star or SIDM particle collisions is much longer than their characteristic crossing (dynamical) time scale, but shorter than the system lifetime. The fluid conduction model reliably tracks the "gravothermal catastrophe" in star clusters and SIDM halos without black holes. For a star cluster with a massive, central black hole, this approximation reproduces the familiar Bahcall-Wolf quasistatic density cusp for the stars bound to the black hole and shows how the cusp halts the "gravothermal catastrophe" and causes the cluster to re-expand. An SIDM halo with an initial black hole central density spike that matches onto to an exterior NFW profile relaxes to a core-halo structure with a central density cusp determined by the velocity dependence of the SIDM interaction cross section. The success and relative simplicity of the fluid conduction approach in evolving such "weakly collisional," quasiequilibrium Newtonian systems motivates its extension to relativistic systems. We present a general relativistic extension here.
我们采用流体传导近似来研究球状星团和自相互作用暗物质（SIDM）晕的演化。我们还探讨了由于存在大质量中心黑洞而在这两个系统中出现的密度尖点的形成及其动力学影响。我们所处理的大N体自引力系统是“弱碰撞”的：恒星或SIDM粒子碰撞之间的平均自由时间远长于它们的特征穿越（动力学）时间尺度，但短于系统寿命。流体传导模型能够可靠地追踪没有黑洞的星团和SIDM晕中的“引力热灾变”。对于一个拥有大质量中心黑洞的星团，这种近似再现了与黑洞束缚的恒星所熟悉的巴卡尔 - 沃尔夫准静态密度尖点，并展示了尖点如何阻止“引力热灾变”并导致星团重新膨胀。一个具有初始黑洞中心密度尖峰且与外部NFW剖面匹配的SIDM晕会弛豫到一个核心 - 晕结构，其中心密度尖点由SIDM相互作用截面的速度依赖性决定。流体传导方法在演化此类“弱碰撞”准平衡牛顿系统方面的成功和相对简单性促使我们将其扩展到相对论系统。我们在此给出一个广义相对论扩展。
