Physics and Astrophysics of Compact Binaries

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The principal objective of this award is to exploit gravitational-wave observations to gain a deeper understanding of gravity and compact objects. Its long-term goals are: (1) to maximize the scientific payoff from gravitational-wave observations: what can we learn about fundamental gravitational physics, and how will compact binary detections contribute to our understanding of the Universe? (2) to improve our theoretical understanding of compact objects, whether isolated or in binaries, in general relativity and in modified theories of gravity. With the expected increase in volume coverage of LIGO/Virgo and the operation of KAGRA in Japan, this work is timely, geared at enhancing the scope of the physics and astrophysics enabled by ground-based interferometers. The project will train a student in a highly interdisciplinary field that requires expertise in general relativity, astrophysics, data analysis and high-energy physics. The PI's newly established group at Johns Hopkins University (JHU) in Baltimore has long-standing collaborations with groups in the US and in the EU. This network of collaborations will ensure that the student funded by this project will be trained in a vibrant international environment. A key goal of the project is to strengthen collaborations between the gravitational physics community and the larger physics and astrophysics communities at a crucial time for the nascent field of gravitational-wave astronomy. JHU has formal collaborations with the Space Telescope Science Institute (STScI) and NASA Goddard (GSFC) and it is home to many world-leading experts in cosmology and astrophysics, so this task will benefit enormously from the group's daily interactions with JHU faculty and STScI astronomers. The PI has a strong track record of training students and postdocs who developed into leading experts working at the interface of these different fields.The first gravitational-wave detections by the LIGO/Virgo collaboration were a major milestone. Large financial resources have been invested in detector design and in compact binary detection templates, but for gravitational-wave science to make even more groundbreaking contributions we must be able to go beyond detections, extracting fundamental physics from the strong-gravity dynamics of the sources. The PI will investigate the structure and dynamics of compact objects in general relativity and in some well-motivated modified theories of gravity. The theoretical insight gained from these investigations will be used to devise a parametrized, theory-agnostic gravitational-wave data analysis framework to quantify dynamical deviations from general relativity for compact binary mergers in the strong-field regime. To address this problem, the PI's group will adopt the following strategy: (1) identify the simplest, best-motivated modified theories of gravity and physics beyond the Standard Model that would produce black hole spacetimes and/or binary black hole gravitational waveforms that differ from general relativity; (2) compute the corresponding black hole solutions and (whenever possible) the gravitational waves emitted during binary merger and ringdown using a combination of perturbation theory and/or numerical relativity; (3) use these results to learn lessons on how to parametrize strong-field deviations from general relativity in a theory-agnostic way, and implement these parametrizations in gravitational-wave data analysis.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.