NUMERICAL EVOLUTION OF DYNAMIC 3D BLACK-HOLES - EXTRACTING WAVES

We consider the numerical evolution of dynamic black hole initial data sets with a full 3D, nonlinear evolution code. These data sets consis t of single black holes distorted by strong gravitational waves, and m imic the late stages of coalescing black holes. Through comparison wit h results from well established axisymmetric codes, we show that these dynamic black holes can be accurately evolved. In particular, we show that with present computational resources and techniques, the process of excitation and ringdown of the black hole can be evolved, and one can now extract accurately the gravitational waves emitted from the 3D Cartesian metric functions, even though they may be buried in the met ric at levels on the order of 10(-3) and below. Waveforms for both the l=2 and the much more difficult l=4 modes are computed and compared w ith axisymmetric calculations. In addition to exploring the physics of distorted black hole data sets, and showing the extent to which the w aves can be accurately extracted, these results also provide important testbeds for all fully nonlinear numerical codes designed to evolve b lack hole spacetimes in 3D, whether they use singularity avoiding slic ings, apparent horizon boundary conditions, or other evolution methods .