The likely detection of gravitational waves will open a new window for astronomy and provide new tests of Einstein's theory of general relativity. Interpreting the observations will require accurate theoretical gravitational waveforms calculated from the theory. This project will contribute to testing general relativity by solving the equations of motion and wave generation of an important alternative theory, known as scalar-tensor gravity, systematically in a post-Newtonian approximation. The calculated waveforms will be used to assess the bounds on this class of theories that could be achieved by ground-based detectors such as the LIGO-Virgo network. We also will study whether binary black hole systems in these theories are observationally identical to their general relativistic counterparts, extending earlier conjectures by Penrose and Hawking. 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 distribution of dark-matter particles very close to the black hole will be determined using a fully general relativistic calculation that extends and corrects earlier approaches. The effects of general relativity on the structure and long-term evolution of clusters of stars around massive black holes will be studied using both analytic means and N-body simulations.
The work on gravitational waves in scalar-tensor theories will impact gravitational-wave observations, as the equations developed in this project will likely be incorporated into the data-analysis pipelines of the detectors. The project on testing general relativity at the galactic center has strong links to many astronomical studies of the center of our galaxy. In the course of this project a post-doctoral researcher and graduate students will learn both the fundamental theory of general relativity, along with many aspects of astrophysics, gravitational-wave detection, and astronomical observations, thereby developing a broad array of tools that they will be able to use in their future careers. 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. The PI has also recently completed a major textbook on Newtonian and post-Newtonian gravity (with Eric Poisson), and plans to update his classic review article on experimental gravitation for the web-based journal Living Reviews in Relativity, and to revamp and update his book Theory and Experiment in Gravitational Physics. He will also be writing a number of specially commissioned review articles celebrating the centenary of general relativity, in 2015.
