We study the head-on collision of two equal-mass momentarily stationary black holes, using black hole perturbation theory up to second order. Compared to first-order results, this significantly improves agreement with numerically computed waveforms and energy. Much more important, second-order results correctly indicate the range of validity of perturbation theory. This use of second-order, to provide ``error bars,'' makes perturbation theory a viable tool for providing benchmarks for numerical relativity in more generic collisions and, in some range of collision parameters, for supplying waveform templates for gravitational wave detection.
@article{arxiv.gr-qc/9609022,
title = {Colliding black holes: how far can the close approximation go?},
author = {Reinaldo Gleiser and Oscar Nicasio and Richard Price and Jorge Pullin},
journal= {arXiv preprint arXiv:gr-qc/9609022},
year = {2009}
}