This award will support research in relativity and relativistic astrophysics. A large component of the research is aimed at the numerical solution of Einstein's equations by supercomputer simulations. One focus is to track the coalescence and merger of binary black hole systems and to calculate the gravitational waveform emitted by such processes. These processes are primary targets for gravitational wave detectors now being deployed, like LIGO, and there is an urgent need for reliable waveforms. The numerical solution of this problem has proved to be remarkably difficult, but recent breakthroughs have led to spectacular progress. The investigators will use a computational technique, pseudospectral collocation, that promises to deliver high accuracy with a much smaller computational cost than other techniques. This technique has been successful in many other areas of the physical sciences, and shows great promise for numerical relativity. A second focus of the research is to study the coalescence and merger of binary systems containing a neutron star and a black hole, or two neutron stars. These are also prime scientific targets for LIGO. The third project is to study r-modes in neutron stars. These are a kind of oscillation of neutron stars, named for their similarity to Rossby waves in the Earth's atmosphere. The investigators will determine the effect of these oscillations on setting the spin rate of observed pulsars and low-mass X-ray binaries, and whether they can lead to detectable signals for LIGO. This research will have a broad impact on our understanding of fundamental physics. There are currently no real tests of general relativity in the strong field regime of black holes. For experiments like LIGO to confront theory with observation, one must be able to calculate what the theory predicts. Are the black holes that LIGO may observe the black holes predicted by Einstein's theory? The research will also have an impact on the broader area of computational science. The computational techniques to be developed here can be used to solve problems in many other areas, including fluid dynamics, meteorology, seismology, and astrophysics. Young researchers trained in these techniques are in great demand.
