Cauchy-perturbative matching and outer boundary conditions:   computational studies
  We present results from a new technique which allows extraction of gravitational radiation information from a generic three-dimensional numerical relativity code and provides stable outer boundary conditions. In our approach we match the solution of a Cauchy evolution of the nonlinear Einstein field equations to a set of one-dimensional linear equations obtained through perturbation techniques over a curved background. We discuss the validity of this approach in the case of linear and mildly nonlinear gravitational waves and show how a numerical module developed for this purpose is able to provide an accurate and numerically convergent description of the gravitational wave propagation and a stable numerical evolution. 
Luciano Rezzolla, Andrew M. Abrahams, Richard A. Matzner, Mark E.   Rupright and Stuart L. Shapiro