重建早期原初黑洞主导时期的引力波背景
Reconstructing Early Primordial Black Hole Domination from Gravitational-Wave Backgrounds
- Jagiellonian University（雅盖隆大学）
- University of Southampton（南安普顿大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究利用原初引力波背景的特征频率，建立数值关系以重建原初黑洞的质量与初始丰度，并表明NANOGrav信号已可探测4-90兆克范围的原初黑洞。
AI中文摘要：
质量低于$\mathcal{O}(10^9)$克的原初黑洞（PBHs）占据了一个常规观测基本无法触及的有趣参数空间区域。尽管这些原初黑洞在大爆炸核合成（BBN）之前就已蒸发，它们却能在早期宇宙中自然产生一段早期物质主导时期。原初引力波背景（GWB）为探测这一难以触及的时期提供了窗口，因为修改后的膨胀历史会留下与PBH主导开始和结束相关的特征谱特征。这些特征频率的位置可用于重建潜在的原初黑洞参数，特别是原初黑洞质量。对于自由传播的引力波背景，这些频率的位置还能额外确定原初黑洞的初始丰度。我们推导出简单的数值关系，将这些特征频率直接映射到原初黑洞质量和初始丰度上。未来的引力波实验覆盖了广泛的频率范围，能够探测从BBN界限$\mathcal{O}(10^9)$克到下限$\mathcal{O}(10)$克之间的原初黑洞质量。我们发现，NANOGrav报告的纳赫兹信号，如果其来源是原初的，已经在探测$4$--$90\\,\mathrm{Mg}$范围内的原初黑洞质量。因此，引力波观测为探索原初黑洞参数空间中一个广阔的区域提供了途径，而这一区域目前超出了现有实验的探测能力。
英文摘要：
Primordial Black Holes (PBHs) with masses below $\mathcal{O}(10^9)$g occupy an interesting region of parameter space that is largely inaccessible to conventional observations. Despite evaporating before Big Bang Nucleosynthesis (BBN), these PBHs can naturally generate a period of early matter domination in the early Universe. A primordial gravitational-wave background (GWB) provides a window onto this otherwise inaccessible regime, since the modified expansion history leaves a characteristic spectral feature associated with the onset and end of PBH domination. The locations of these characteristic frequencies can be used to reconstruct the underlying PBH parameters, in particular the PBH mass. For a freely propagating GWB, the location of these frequencies additionally allow the initial PBH abundance to be determined. We derive simple numerical relations that map these characteristic frequencies directly onto the PBH mass and initial abundance. Future GW experiments span a vast frequency range, providing sensitivity to PBH masses from the BBN bound of $\mathcal{O}(10^9)\,\mathrm{g}$ down to the lower bound of $\mathcal{O}(10)\,\mathrm{g}$. We find that the nanohertz signal reported by NANOGrav, if primordial in origin, is already probing PBH masses in the range $4$--$90\,\mathrm{Mg}$. GW observations therefore offer access to a vast region of PBH parameter space that is otherwise beyond the reach of current experiments.
