Initial Perturbations on Ultra-Small Scales and Primordial Black Holes in the Era of Gravitational-Wave Astronomy

该奖项资助了纽约大学的Yacine Ali-Haimoud教授的研究活动。经过几十年越来越详细的观测，人们已经确定宇宙中含有大量未知物质，这些物质与已知形式的物质几乎没有相互作用。了解这种“暗物质”的性质是物理学中尚未解决的主要问题之一。 原始黑洞（PBH）是迷人的暗物质候选者。 PBH可能在婴儿宇宙中形成，甚至在第一颗恒星存在之前。 Ali-Haimoud教授的目标是通过预测它们对早期宇宙地图的影响和检查它们将发出的引力波，并将这些预测与观测结果进行比较，来开发PBH的测试。此外，他将开发一种新的方法来研究宇宙的初始条件，通过量化它们对某些宇宙相变的影响。 因此，这项研究通过促进美国基础科学的进步来服务于国家利益。 这项研究也将产生更广泛的影响。 Ali-Haimoud教授将把这项研究的结果纳入他的研究生和本科生物理课程，并直接让学生参与这些调查。 此外，他还将为服务水平低下的纽约市高中生开设一门关于航海物理学的课程，他希望通过将航海与引力波和黑洞进行比较来培养对物理学的热情。更具体地说，这项研究的第一个和主要重点是通过对宇宙微波背景（CMB）各向异性的影响，特别是对激光干涉仪引力波天文台（LIGO）的引力波信号，对大约一到一千个太阳质量的PBH的丰度建立鲁棒的限制。 Ali-Haimoud教授将把他对PBH双星合并率的分析计算扩展到现实的质量分布，估计由此产生的随机引力波背景占高偏心率，并通过数值模拟确定在早期宇宙中形成的PBH双星是否受到非线性结构的显著影响。 他还将通过估计吸积PBH的自洽光度和研究吸积的性质（球形与盘状）来扩展他在CMB极限上的工作。 第二个项目涉及探索一个全新的想法：小尺度重子微扰对全局重组历史的影响。 这一效应可以用来研究当前无约束的小尺度重子等曲率微扰。 Ali-Haimoud教授将通过研究复合过程中莱曼α线的扰动辐射传输来定量地探索这一想法。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award funds the research activities of Professor Yacine Ali-Haimoud at New York University.After decades of increasingly detailed observations, it is well established that the Universe contains a large amount of unknown matter that interacts little, if at all, with known forms of matter. Understanding the nature of this "dark matter" is one of the major unsolved problems in physics. Primordial black holes (PBH's) are fascinating dark-matter candidates. PBH's could have formed in the infant Universe, before the first stars even existed. Professor Ali-Haimoud aims to develop tests of PBH's by predicting their effect on maps of the early Universe and examining the gravitational waves they would emit, and by comparing these predictions with observations. In addition, he will develop a novel way to study the initial conditions of the Universe by quantifying their impact on certain cosmological phase transitions. As such, this research serves the national interest by promoting the progress of fundamental science in the United States. This research will also have significant broader impacts. Professor Ali-Haimoud will include the results of this research in his graduate and undergraduate physics courses and will also directly engage students in these investigations. In addition, he will develop a course for underserved New York City high-school students on the physics of sailing in which he hopes to foster enthusiasm for physics by drawing parallels between sailing and gravitational waves and black holes. More specifically, the first and main focus of this research is to establish robust limits on the abundance of PBH's of about one to one thousand solar masses through their impact on cosmic microwave background (CMB) anisotropies, and especially their gravitational-wave signals for the Laser Interferometer Gravitational-Wave Observatory (LIGO). Professor Ali-Haimoud will extend his analytic calculations of the merger rate of PBH binaries to realistic mass distributions, estimate the resulting stochastic gravitational-wave background accounting for high eccentricities, and establish through numerical simulation whether PBH binaries formed in the early Universe are significantly affected by non-linear structures. He will also extend his work on CMB limits by estimating the self-consistent luminosity of accreting PBH's, and by studying the nature of accretion (spherical vs. disk-like). The second project involves exploring an entirely new idea: the impact of small-scale baryon perturbations on the global recombination history. This effect can probe the currently unconstrained small-scale baryon isocurvature perturbation. Professor Ali-Haimoud will explore this idea quantitatively by studying perturbed radiative transfer in the Lyman-alpha line during recombination.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.