The principle part of Einstein equations in the harmonic gauge consists of a constrained system of 10 curved space wave equations for the components of the space-time metric. A new formulation of constraint-preserving boundary conditions of the Sommerfeld type for such systems has recently been proposed. We implement these boundary conditions in a nonlinear 3D evolution code and test their accuracy.
@article{arxiv.gr-qc/0612051,
title = {Constraint-preserving Sommerfeld conditions for the harmonic Einstein equations},
author = {M. C. Babiuc and H-O. Kreiss and Jeffrey Winicour},
journal= {arXiv preprint arXiv:gr-qc/0612051},
year = {2009}
}