APPLYING BLACK-HOLE PERTURBATION-THEORY TO NUMERICALLY GENERATED SPACETIMES

Nonspherical perturbation theory has been necessary to understand the meaning of radiation in spacetimes generated through fully nonlinear n umerical relativity. Recently, perturbation techniques have been found to be successful for the time evolution of initial data found by nonl inear methods. Anticipating that such an approach will prove useful in a variety of problems, we give here both the practical steps, and a d iscussion of the underlying theory, for taking numerically generated d ata on an initial hypersurface as initial value data and extracting da ta that can be considered to be nonspherical perturbations.