COORDINATE CONDITIONS IN 3-DIMENSIONAL NUMERICAL RELATIVITY

We put forward a few ideas on coordinate (gauge) conditions in numeric al relativity. Coordinate conditions are important for long time scale simulations of relativistic systems. We demonstrate the importance of , and propose methods for, the active enforcement of coordinate proper ties. In particular, the constancy of the determinant of the spatial 3 -metric is investigated as such a property. We propose an exceedingly simple but powerful idea for implementing elliptic coordinate conditio ns that not only makes possible the use of complicated elliptic condit ions, but is also a number of orders of magnitude more efficient than existing methods for large-scale three-dimensional simulations.