Exploring Strong-Field Gravity through Gravitational-Wave and Multimessenger Observations

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

The overarching goal of this project is to reveal how well one can ultimately probe the nature of strong, dynamical, and nonlinear gravity through gravitational-wave observations of black holes and multimessenger observations of neutron stars. Currently, one of the biggest challenges in testing General Relativity with gravitational waves from binary black hole coalescences is the lack of complete gravitational waveforms from theories beyond General Relativity that are valid throughout the inspiral, merger, and ringdown of the binary evolution. Moreover, for binary neutron stars, certain tests of General Relativity are limited by uncertainties in nuclear matter properties. The PI will tackle these problems by (I) constructing, for the first time, gravitational waveforms in theories beyond General Relativity that are valid in all of the inspiral-merger-ringdown phases, and (II) performing a comprehensive study of multimessenger tests of General Relativity with neutron star observations by avoiding uncertainties in nuclear physics. The gravitational waveform models to be developed will be ready to use and can be widely adopted by the gravitational wave community and beyond. Multimessenger tests of General Relativity with neutron star observations are extremely timely, and the outcome of both projects will impact various communities in physics and beyond, including gravitational physics, particle physics, nuclear physics, and astrophysics. The long-term educational goal of the project is to connect, globally, potential next-generation scientists and convey the beauty and excitement of physics, in particular General Relativity. For the construction of the complete gravitational waveforms, the PI will work in a specific gravitational theory motivated by string theory, in which some simulations are already available. The PI and collaborators will produce more simulation data for the merger-ringdown and will stitch them against analytic waveforms during the inspiral. These complete waveforms allow one to probe more precisely theories beyond General Relativity with the existing gravitational wave events and will assist in searches for new physics with future observations. For multi-messenger tests, the PI will employ universal relations among certain neutron star observables that do not depend sensitively on the unknown internal structure of neutron stars. The PI will study such relations in a few theories beyond General Relativity that either introduce additional scalar/vector fields or introduce modifications in the high curvature regime. The PI will then study how well one can probe these theories through current and future multimessenger observations. To achieve the educational goal, the PI's team will develop an online game on General Relativity and gravitational waves to reach out to young players across the world. In the game instructions, the PI will provide a brief description of General Relativity, black holes, and gravitational waves, conveying the excitement and key aspects of recent Nobel-prize winning physics. Some students will be involved in the game development, integrating the research and educational activities. The PI will make the source codes publicly available so that anyone can develop their own games. 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.