Testing General Relativity with Gravitational Wave Observations

This award supports research in relativity and relativistic astrophysics, and it addresses the priority areas of NSF's "Windows on the Universe" Big Idea. The past two decades have witnessed compounding problems in observational cosmology that simply don’t go away: the accelerated expansion of the Universe, tension between the local and early Universe epoch measurements of the Hubble constant, and non-detection of dark matter are prime examples of crises in physics. A multitude of effort is being made to better understand these problems as one does not know where the problem might be. Modified gravity theories are seen as one possible solution. Likewise, conceptual problems in general relativity need to be examined observationally from a variety of different approaches to be successful. This award will test general relativity in ways complementary to other tests (e.g. the black hole no-hair test) and probe the strong-field regime of gravity, making the full use of the signal. These tests will either detect violation of general relativity or constrain certain modified theories of gravity that have been invoked to explain the aforementioned cosmological problems.General Relativity has been a tremendously successful theory in explaining current astronomical observations and laboratory experiments. Nevertheless, there is a general consensus that the theory is at best incomplete, representing an approximation to a more complete theory that cures some or all of its problems. The work supported by this grant is takes a two-pronged approach to explore general relativistic violations: 1. Measure the multipolar structure of the observed radiation to test for self-consistency of general relativity. 2. An incoherent, time-frequency test that checks for consistency of the observed signal-power in different multipoles with the predictions of general relativity. The tests will improve upon the current approach in two significant ways. Firstly, for binaries with large mass asymmetry (m1/m2>2) and orbital inclinations more than 30 degrees one can expect appreciable signal power in higher order multipoles. Secondly, by making use of the full inspiral-merger-ringdown signal in the analysis increases the signal-to-noise ratio in higher modes.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.