%0 Journal Article
%T Finding Principal Null Direction for Numerical Relativists
%A Laurens Gunnarsen
%A Hisa-aki Shinkai
%A Kei-ichi Maeda
%J Physics
%D 1994
%I arXiv
%R 10.1088/0264-9381/12/1/011
%X We present a new method for finding principal null directions (PNDs). Because our method assumes as input the intrinsic metric and extrinsic curvature of a spacelike hypersurface, it should be particularly useful to numerical relativists. We illustrate our method by finding the PNDs of the Kastor-Traschen spacetimes, which contain arbitrarily many $Q=M$ black holes in a de Sitter back-ground.
%U http://arxiv.org/abs/gr-qc/9406003v1