论文标题
原始黑洞的引力波约束以早期宇宙为主
Gravitational wave constraints on the primordial black hole dominated early universe
论文作者
论文摘要
我们计算由于PBHS最终通过霍克蒸发而占主导地位并重新加热宇宙的情况下，由于原始黑洞（PBH）的不均匀分布引起的密度波动引起的重力波（GWS）。最初的PBH密度波动本质上是等异性的。我们发现，当宇宙从PBH统治时代到以辐射为主时，蒸发后，大多数诱导的GW是在蒸发后立即产生的，而曲率扰动开始狂奔。对产生的GW的量的最强限制来自大爆炸核合成（BBN）。我们改善了对PBH分数的先前约束，发现它不能超过$ 10^{ - 3} $。此外，随着质量的增加，此最大分数减小，并达到$ 10^{ - 9} $，对于$ M _ {\ rm pbh} \ sim 5 \ sim 5 \ times10^8 {\ rm g} $，这是BBN在重组温度上允许的最大质量。考虑到PBH可能会在给定的聚类量表上群集高于给定的聚类量表，因此我们在聚类范围内也得出了一个下限。有趣的是，$ m _ {\ rm pbh} \ sim 10^4 -10^8 {\ rm g} $进入Ligo和decigo的观察窗口的GW频谱将来可以在将来进行测试。尽管我们专注于本文主导的早期宇宙的PBH，但我们的方法论适用于任何具有早期外部扰动的模型。
We calculate the gravitational waves (GWs) induced by the density fluctuations due to inhomogeneous distribution of primordial black holes (PBHs) in the case where PBHs eventually dominate and reheat the universe by Hawking evaporation. The initial PBH density fluctuations are isocurvature in nature. We find that most of the induced GWs are generated right after evaporation, when the universe transits from the PBH dominated era to the radiation dominated era and the curvature perturbation starts to oscillate wildly. The strongest constraint on the amount of the produced GWs comes from the big bang nucleosynthesis (BBN). We improve previous constraints on the PBH fraction and find that it cannot exceed $10^{-3}$. Furthermore, this maximum fraction decreases as the mass increases and reaches $10^{-9}$ for $M_{\rm PBH}\sim 5\times10^8 {\rm g}$, which is the largest mass allowed by the BBN constraint on the reheating temperature. Considering that PBH may cluster above a given clustering scale, we also derive a lower bound on the scale of clustering. Interestingly, the GW spectrum for $M_{\rm PBH}\sim 10^4 -10^8 {\rm g}$ enters the observational window of LIGO and DECIGO and could be tested in the future. Although we focus on the PBH dominated early universe in this paper, our methodology is applicable to any model with early isocurvature perturbation.
