The LIGO/Virgo collaboration have by now detected the mergers of ten black hole binaries via the emission of gravitational radiation. The hypothesis that these black holes have formed during the cosmic QCD epoch and make up all of the cosmic dark matter, has been rejected by many authors reasoning that, among other constraints, primordial black hole (PBH) dark matter would lead to orders of magnitude larger merger rates than observed. We revisit the calculation of the present PBH merger rate. Solar mass PBHs form clusters at fairly high redshifts, which evaporate at lower redshifts. We consider in detail the evolution of binary properties in such clusters due to three-body interactions between the two PBH binary members and a third by-passing PBH, for the first time, by full numerical integration. A Monte-Carlo analysis shows that formerly predicted merger rates are reduced by orders of magnitude due to such interactions. The natural prediction of PBH dark matter formed during the QCD epoch yields a pronounced peak around 1M⊙ with a small mass fraction of PBHs on a shoulder around 30M⊙, dictated by the well-determined equation of state during the QCD epoch. We employ this fact to make a tentative prediction of the merger rate of ~ 30M⊙ PBH binaries, and find it very close to that determined by LIGO/Virgo. Furthermore we show that current LIGO/Virgo limits on the existence of ~ M⊙ binaries do not exclude QCD PBHs to make up all of the cosmic dark matter. Neither do constraints on QCD PBHs from the stochastic gravitational background, pre-recombination accretion, or dwarf galaxies pose a problem. Microlensing constraints on QCD PBHs should be re-investigated. We caution, however, in this numerically challenging problem some possibly relevant effects could not be treated.

中文翻译：

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原始黑洞暗物质和 LIGO/Virgo 观测

LIGO/Virgo 合作现在已经通过引力辐射的发射探测到十个黑洞双星的合并。这些黑洞是在宇宙 QCD 时期形成并构成所有宇宙暗物质的假设，已被许多作者拒绝，理由是除其他限制外，原始黑洞 (PBH) 暗物质将导致数量级比观察到的更大的合并率。我们重新审视当前 PBH 合并率的计算。太阳质量 PBHs 在相当高的红移处形成星团，在较低的红移处蒸发。由于两个 PBH 二元成员和第三个旁路 PBH 之间的三体相互作用，我们首次通过完全数值积分详细考虑了此类簇中二元性质的演变。蒙特卡罗分析表明，由于这种相互作用，以前预测的合并率降低了几个数量级。在 QCD 时期形成的 PBH 暗物质的自然预测在 1M⊙ 附近产生了一个明显的峰值，在 30M⊙ 左右的肩部上有少量 PBH 的质量分数，这是由 QCD 时期确定的状态方程决定的。我们利用这一事实对~30M⊙ PBH 双星的合并率进行了初步预测，发现它与 LIGO/Virgo 确定的合并率非常接近。此外，我们表明当前 LIGO/Virgo 对~M⊙ 双星存在的限制并不排除 QCD PBH 来构成所有宇宙暗物质。随机引力背景、重组前吸积或矮星系对 QCD PBH 的约束也不构成问题。应重新研究对 QCD PBH 的微透镜限制。然而，我们警告说，在这个数值上具有挑战性的问题中，一些可能相关的影响无法处理。