Testing General Relativity principles with Neutron Stars, Black Holes, and Gravitational Waves

Embry-Riddle Aeronautical University, Daytona Beach FL

Investigators

Abstract

Einstein's General Relativity and quantum physics are the currently accepted theories describing physics across the universe. General Relativity is a comprehensive description of observed gravitational phenomena on scales ranging from micrometers to the size of the visible universe. Quantum physics describes, to a high degree of precision, the molecular, atomic and subatomic regime. Despite the success, unresolved questions remain in cosmology and quantum gravity, and so physicists worldwide conjecture that the two theories are merged in some unknown unified theory. Recent scientific literature reveals that experiments and observation could possibly find violations in the foundations of General Relativity theory. Such foundational principles include the notion of spacetime symmetry. For example, local experiments should not favor any special direction in space, according to General Relativity. However, models of quantum gravity suggest that this principle may be broken in a miniscule but detectable way. The work supported by this award involves theoretical calculations of signals for spacetime symmetry breaking in experiments and observations. The focus will be on using astrophysical phenomena like black holes and gravitational waves. One of the important aspects of this award is financial support for undergraduate research in theory. This has the impactful feature of not only assisting the PI in the work, but also giving research experience to students, thus contributing to their education and increasing the likelihood of future STEM careers. Outreach opportunities by the PI and students are also supported. The work in this award on tests of the foundations of General Relativity will use a broad test framework, based on effective field theory. Signals for spacetime-symmetry violations, like local Lorentz violation and diffeomorphism symmetry violation, will be calculated for black holes and gravitational waves. Within the effective field theory framework, strong-field gravity solutions for the spacetime metric for black holes, modified by generic spacetime-symmetry violation, will be constructed, representing a new step forward in this area. Modification to gravitational wave generation is to be studied, complementing existing analysis on propagation effects. The work is closely tied to finding specific observables that can be tested against experiments and observations. Thus, the award supports theoretical work that will provide motivation and additional areas in which to search for new physics beyond General Relativity, in particular, in gravitational wave observations. 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.