Relativistic Gravitation and Astrophysics

University Of Florida, Gainesville FL

Investigators

Abstract

The recent detections of gravitational waves by the LIGO observatories in the USA have demonstrated a new way of "hearing" the universe using ripples in spacetime, and have provided stunning new tests of Einstein's theory of general relativity. Observations by astronomers of the motions of stars and gas near supermassive black holes, such as the one at the center of the Milky Way, have opened the possibility of testing Einstein's theory in realms where the warping of spacetime is extreme. Yet in order to test Einstein's great theory, it is essential to know what it actually predicts for real measurements. This project continues a program of research to provide concrete links between the abstract beauty and complex mathematics of Einstein's theory and the real world where measurements are made by physicists and astronomers. These links are established by finding approximate, yet accurate solutions of the equations in forms that are practical and usable. The solutions developed in this research will be used by data experts at the gravitational-wave observatories to perform better tests of general relativity using newly detected signals, and will be used by astronomers to probe how the warped spacetime near massive black holes affects stars orbiting such objects. Einstein's theory is a topic that fascinates the general public, and the PI will continue to give public lectures on topics related to this research, bringing understanding of Einstein's ideas to the broader community. Specifically, this project will contribute to the ability of ground-based gravitational-wave observatories such as the LIGO-Virgo network to test general relativity, by computing the equations of motion for binary star systems, along with the emitted gravitational waveforms, as predicted by an important alternative theory, known as scalar-tensor gravity, to high accuracy in the so-called post-Newtonian approximation. It will provide accurate waveforms predicted by this theory in a format that can be adapted to LIGO-Virgo data analysis methods. The approach extends a method known as Direct Integration of the Relaxed Einstein Equations that has been developed over many years by the PI and his collaborators. The possibility of testing general relativity in the vicinity of the massive black hole in the center of our galaxy using future infrared telescopes, proposed by the PI in 2008, will be investigated further. The effects of general relativity on the structure and long-term evolution of clusters of stars around massive black holes will be studied using analytic means based on the post-Newtonian approximation.