Dynamics of primordial black hole formation
Dynamics of primordial black hole formation
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DOI：
10.1103/physrevd.59.124013
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发表时间：
1999-01
影响因子：
5
通讯作者：
J. Niemeyer;K. Jedamzik
中科院分区：
文献类型：
--
作者：
J. Niemeyer;K. Jedamzik
我们对早期宇宙辐射为主阶段视界大小密度涨落对原始黑洞(PBH)的引力崩塌进行了数值研究。计算了穿越水平时施加的三种不同初始摄动形状的坍塌动力学。如果将黑洞形成的微扰阈值定义为初始视界体积内的相对过剩质量，则估算宇宙黑洞质量函数所需的微扰阈值是${\ensuremath{\delta}}_{\mathrm{c}}\ensuremath{\approx}0.7$而不是通常使用的${\ensuremath{\delta}}_{\mathrm{c}}\ensuremath{\approx}1/3$。为了研究新形成的黑洞的吸积，我们使用了一个数值格式，它允许我们在事件视界形成后跟踪很长时间的演化。一般来说，小黑洞(与崩塌开始时的地平线质量相比)会产生流体反弹，有效地阻止对黑洞的吸积，而大黑洞则不会。在这两种情况下，由于吸积导致的黑洞质量增长都是微不足道的。此外，黑洞质量随形成阈值的距离的标度，已知发生在近临界引力塌缩中，被证明适用于原始黑洞的形成。
We present a numerical investigation of the gravitational collapse of horizon-size density fluctuations to primordial black holes (PBHs) during the radiation-dominated phase of the early Universe. The collapse dynamics of three different families of initial perturbation shapes, imposed at the time of horizon crossing, is computed. The perturbation threshold for black hole formation, needed for estimations of the cosmological PBH mass function, is found to be ${\ensuremath{\delta}}_{\mathrm{c}}\ensuremath{\approx}0.7$ rather than the generally employed ${\ensuremath{\delta}}_{\mathrm{c}}\ensuremath{\approx}1/3$ if $\ensuremath{\delta}$ is defined as $\ensuremath{\Delta}{M/M}_{\mathrm{h}},$ the relative excess mass within the initial horizon volume. In order to study the accretion onto the newly formed black holes, we use a numerical scheme that allows us to follow the evolution for long times after formation of the event horizon. In general, small black holes (compared to the horizon mass at the onset of the collapse) give rise to a fluid bounce that effectively shuts off accretion onto the black hole, while large ones do not. In both cases, the growth of the black hole mass owing to accretion is insignificant. Furthermore, the scaling of black hole mass with the distance from the formation threshold, known to occur in near-critical gravitational collapse, is demonstrated to apply to primordial black hole formation.