Research on Gravitational Waves and Compact Binaries

在过去的几年里，LIGO和室女座探测器对合并的中子星和恒星质量的黑洞进行了令人兴奋的观测，开启了引力波天文学的时代。这些事件揭示了新的天体物理学，包括证实了重元素的产生过程，发现了一类新的恒星质量重的黑洞，并为广义相对论提供了新的测试。它们还预示着最终对极端质量比激发(EMRI)的引力波观测，即恒星质量的黑洞或中子星螺旋进入超大质量黑洞，例如现在已知存在于几乎所有大型星系中心的超大质量黑洞。这些超大质量黑洞被密集的星团包围，经常会将致密恒星(如中子星或恒星质量黑洞)捕获到高度偏心的轨道上。当这些致密恒星绕轨道运行时，它们发出引力波，导致轨道衰变，致密天体最终被超大质量黑洞吞没。利用未来的空间引力波探测器LISA，可以潜在地观测到所发射的引力辐射。由该奖项资助的理论工作将改进对高度偏心的紧凑合并双星的预期信号的预测。从这种EMRI中探测引力波将提供独特的强场引力测试并探索黑洞的本质。为了实现这一努力，将开发黑洞微扰理论和引力自力方法的新技术，并编写相关的高级计算机代码。来自微扰理论和自力计算的高精度结果将被研究，以揭示偏心双星运动和相关引力波发射的后牛顿展开中的高阶项。微扰理论和在极端质量比、后牛顿重叠区的自力发现支持并加强了更广泛的努力，将后牛顿理论提升到更高的阶数，并为合并双星的有效一体机模型提供校准。PI的团队正在将自力计算扩展到Kerr背景上的一般运动，最初使用标量场模型，主要重点是使这些计算更有效率。新的自力技术将与密切元素代码相结合，以建立偏心EMRI的长期螺旋模型。这项工作的一些部分将与几名以前的学生和都柏林大学学院的同事进行外部合作。数值和分析结果以及一些计算机代码将在网上公布。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The exciting observations by the LIGO and Virgo detectors of merging neutron stars and stellar-mass black holes over the past several years have opened up the era of gravitational wave astronomy. These events have revealed new astrophysics, including confirming the process through which heavy elements are created and discovering a new class of heavy stellar-mass black holes, and are providing novel tests of general relativity theory. They also herald eventual gravitational wave observations of extreme-mass-ratio inspirals (EMRIs), where a stellar-mass black hole or neutron star spirals into a supermassive black hole, such as those now known to exist in the center of virtually all large galaxies. Surrounded by dense star clusters, these supermassive black holes will frequently capture compact stars (e.g., neutrons stars or stellar mass black holes) into highly eccentric orbits. As these compact stars orbit, they radiate gravitational waves, causing the orbit to decay and the compact object to eventually be swallowed by the supermassive black hole. The emitted gravitational radiation is potentially observable with LISA, the future space-based gravitational wave detector. The theoretical work funded by this award will provide improved predictions of the expected signals from highly-eccentric compact merging binaries. Detection of gravitational waves from such EMRIs will provide unique strong field tests of gravity and probe the nature of black holes.To pursue this effort, development of new techniques in black hole perturbation theory and gravitational self-force methods will be made, along with writing associated advanced computer codes. High precision results from perturbation theory and self-force calculations will be studied to uncover high-order terms in the post-Newtonian expansion of eccentric binary motion and associated gravitational wave emission. Perturbation theory and self-force findings in the extreme-mass-ratio, post-Newtonian overlap region support and reinforce broader efforts to advance post-Newtonian theory to higher orders and provide calibrations for effective-one-body models of merging binaries. The PI's group is extending self-force calculations to generic motion on Kerr backgrounds, using a scalar field model initially, with primary focus to make these computations more efficient. New self-force techniques will be combined with osculating elements codes to build long-term inspiral models for eccentric EMRIs. Some parts of this work will be conducted in external collaboration with several former students and with colleagues at University College Dublin. Numerical and analytic results, as well as some computer codes, will be made available online.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.