Gravitational waves from black hole binaries: modeling, astrophysics and strong-field tests

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Two black holes gradually approaching each other and eventually merging to release a large amount of energy in gravitational waves are one of the most promising sources for gravitational wave observatories, such as LIGO and LISA. One of the main challenges in gravitational wave data analysis consists in extracting the signal emitted by such binaries from the noisy detector output. For the extraction to be successful, accurate theoretical "template" waveforms of the signal are needed. The goal of the research supported by this award is to improve theoretical knowledge of gravitational waveforms from merging black holes. A combination of techniques will be used: (1) a "post-Newtonian" expansion of Einstein's theory of gravity during the early inspiral, when the black holes are far apart and small corrections to Newtonian theory provide a reasonable description of the system; (2) a numerical solution of Einstein's equations when the black holes merge; (3) a technique known as "black hole perturbation theory" when the system finally settles down to a single rotating black hole solution.Black hole collisions will be studied both in the astrophysical context and from a theoretical point of view. Improving knowledge of theoretical waveforms from astrophysical black hole binaries and exploring possible astrophysical implications is timely and relevant for gravitational wave searches in LIGO data, has applications in observational astrophysics, and is of fundamental importance in the planning of LISA. The study of black hole collisions at speeds close to the speed of light is a theoretical investigation that will reveal poorly known details of Einstein's theory of gravity in extreme conditions and will allow a quantitative estimate of the maximum energy and luminosity that can be radiated in a merger, solving long-standing questions in fundamental gravitational physics. This research will provide the opportunity to train a graduate student in gravitational physics.