Dynamical, Strong-Field Gravity

Princeton University, Princeton NJ

Investigators

Abstract

The research goals of this award are focused on understanding the strong-field regime of Einstein's theory of general relativity. This encompasses both astrophysical and theoretical aspects of general relativity. On the astrophysical side, the main effort is the numerical simulation of binary black hole, black hole-neutron star and binary neutron star collisions. This is critical for the nascent field of gravitational wave astronomy that began in 2015 with LIGO's detection of the collision of two black holes. The speed at which the field is advancing is breathtaking, with the first gravitational wave detection of a binary neutron star collision in 2017, accompanied by intense study of the aftermath across the electromagnetic spectrum by a large community of observational astronomers. Numerical models of such events are needed to aid in detection, and are crucial to decipher details of what happened. On the theoretical side, there are many outstanding questions about the nature of spacetime in extreme situations. One example is the behavior of black holes that rotate close to the maximum rate theoretically allowed by Einstein's theory : there have been suggestions that the horizons of such black holes could exhibit some form of turbulent dynamics, and one goal of this award is to investigate those claims. The pursuit of these projects will involve graduate students, undergraduates and postdoctoral fellows. They will be trained to do leading scientific research, become knowledgeable in corresponding areas of physics, and adept in high-performance computing and numerical methods. These skills are invaluable to many professions, and would thus also benefit and further the development of those students and postdocs that subsequently wish to pursue careers outside academia. A specific list of gravitational wave source modeling projects that will be pursued are (1) using properties of the quasi-normal ringdown of the remnant black hole following a binary black hole merger to test general relativity, in particular the uniqueness properties of black holes, (2) constraining certain modified gravity theories using black hole merger observations, (3) developing models of exotic compact object alternatives to black holes to allow concrete predictions of how their merger waveforms differ from those of binary black holes, and hence detect, constrain or rule out such models, and (4) modeling tidal and dissipative effects in the merger of binaries containing neutron stars. To address the problem of turbulence in near-extremal Kerr black holes, the group will continue development of analytical and numerical tools to study perturbations of such black holes to second order in perturbation theory; the outcome of this will guide whether a full numerical code adapted to the problem warrants development. 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.