1. Gravitational Physics Personnel:C. R. Evans B. Brill T. Garrett M. Peppers ResearchSources of Gravitational Radiation Interests:Numerical Relativity & Black Hole Dynamics Critical Phenomena in Gravitational Collapse Gravitational Wave Signal Analysis

2. Gravitational Physics Numerical Integration of 1 st Order Hyperbolic Systems on Black Hole Spacetimes (Brill & Evans) Numerical Implementation and Stability of Black Hole Excision (Garrett & Evans) Ultimate Goal:Simulate Binary Black Hole Mergers in 3 dimensions (3D) Near-Term:Treat Hyperbolic Systems in General Spacetimes in 3D Remove Black Hole Interior from Computational Domain Achieve Stability at the Horizon Achieve Efficient, Scalable Computation on Parallel Computers Employ More General Spatial Coordinate Systems

3. Gravitational Physics Numerical Integration of Scalar Field on a Schwarzschild Black Hole Black Hole Interior is Excised from the Computational Domain Late-time Quasi-normal Mode Develops

4. Gravitational Physics Numerical Integration of Scalar Field on a Kerr Black Hole Black Hole Interior is Excised from the Computational Domain Late-time Spiral Quasi-normal Mode Develops

5. Gravitational Physics Accomplishments: Integration of scalar fields in 1 st order form on black hole spacetimes Stable black hole excision in special coordinate systems Development of a general time-dependent, 2 nd order, operator splitting method Development of a scalable code using MPI on an IBM SP cluster (720 proc’s) Current Activities: Working to develop a black hole excision technique (causal differencing) that can be used with more general spatial coordinate systems Working to extend integrations to 1 st order hyperbolic tensor wave systems Extension to dynamic black holes

6. Gravitational Physics Ultimate Goal: Merger of Kerr Black Holes Holes Precess Orbit Precesses Frame Dragging Non-Kerr Remnant

7. Gravitational Physics Related Publications Evans, C.R. & Coleman, J.S. 1994, “Critical Phenomena and Self-Similarity in the Gravitational Collapse of Radiation Fluid,” Phys. Rev. Lett., 72, 1782. Abrahams, A.M. & Evans, C.R. 1993, “Critical Behavior and Scaling in Vacuum Axisymmetric Gravitational Collapse,” Phys. Rev. Lett., 70, 2980. Abrahams, A.M., Rezzolla, L., Rupright, M.E., et al., 1998, “Gravitational wave extraction and outer boundary conditions by perturbative matching,” Phys. Rev. Lett., 80, 1812-1815. Cook, G.B., Huq, M.F., Klasky, S.A., Scheel, M.A., et al., 1998, “Boosted 3-dimensional Black Hole Evolutions with Singularity Excision,” Phys. Rev. Lett., 80, 2512-2516. Abrahams, A.M. and Evans, C.R. 1990, “Gauge Invariant Treatment of Gravitational Radiation near the Source: Analysis and Numerical Simulations,” Phys. Rev., D42, 2585. Gomez, R., Lehner, L., Marsa, R., Winicour, J., et al., 1998, “Stable characteristic evolution of generic 3-dimensional single-black-hole spacetimes,” Phys. Rev. Lett., 80, 3915-3918.