Jedamzik Karsten
Laboratoire de Univers et Particules de Montpellier, UMR5299-CNRS, Universite de Montpellier, 34095 Montpellier, France.
Phys Rev Lett. 2021 Feb 5;126(5):051302. doi: 10.1103/PhysRevLett.126.051302.
The LIGO/Virgo Collaboration has by now observed or constrained the gravitational merger rates of different classes of compact objects. We consider the possibility that the bulk of these mergers are primordial black hole (PBH) mergers of PBHs formed during the QCD epoch making up the entirety of the dark matter. Having shown in a companion paper that mergers due to the initial binary population formed in the early Universe are likely negligible, we compute current merger rates in PBH clusters in which the typical PBH resides. We consider two scenarios: (i) the PBH mass function dictated by the QCD equation of state and (ii) the PBH mass function dictated by the existence of a peak in the inflationary perturbation spectrum. In the first scenario, which is essentially parameter-free, we reproduce very well the merger rates for heavy BHs, the merger rate of mass-asymmetric BHs such as GW190814, a recently discovered merger of a 23 M_{⊙} black hole with a 2.6 M_{⊙} object, and can naturally explain why LIGO/Virgo has not yet observed mergers of two light PBHs from the dominant ∼1 M_{⊙} PBH population. In the second scenario, which has some parameter freedom, we match well the observed rate of heavy PBHs but can currently not explain the rate for mass-asymmetric events. In either case, it is tantalizing that in both scenarios PBH merger rates made with a minimum of assumptions match most LIGO/Virgo observed rates very well.
激光干涉引力波天文台（LIGO）/处女座（Virgo）合作组织目前已经观测到或限制了不同类型致密天体的引力合并率。我们考虑了这样一种可能性，即这些合并事件中的大部分是在量子色动力学（QCD）时期形成的原初黑洞（PBH）合并，这些原初黑洞构成了全部暗物质。在一篇配套论文中我们已经表明，早期宇宙中形成的初始双星群体导致的合并可能可以忽略不计，我们计算了典型原初黑洞所在的原初黑洞星团中的当前合并率。我们考虑两种情况：（i）由量子色动力学状态方程决定的原初黑洞质量函数，以及（ii）由暴胀微扰谱中的一个峰值的存在所决定的原初黑洞质量函数。在第一种基本上无参数的情况下，我们很好地再现了重黑洞的合并率、质量不对称黑洞（如GW190814，这是最近发现的一个23 M⊙黑洞与一个2.6 M⊙天体的合并）的合并率，并且可以自然地解释为什么激光干涉引力波天文台/处女座合作组织尚未观测到来自占主导地位的约1 M⊙原初黑洞群体的两个轻原初黑洞的合并。在第二种有一些参数自由度的情况下，我们很好地匹配了观测到的重原初黑洞的速率，但目前无法解释质量不对称事件的速率。在任何一种情况下，令人感兴趣的是，在这两种情况下，在最少假设下得出的原初黑洞合并率都与激光干涉引力波天文台/处女座合作组织观测到的大多数速率非常匹配。
