Hyperbolic formulations and numerical relativity: Experiments using Ashtekar's connection variables

In order to perform accurate and stable long-time numerical integration of the Einstein equation, several hyperbolic systems have been proposed. Here we present a numerical comparison between weakly hyperbolic, strongly hyperbolic and symmetric hyperbolic systems based on Ashtekar's connection variables. The primary advantage for using this connection formulation in this experiment is that we can keep using the same dynamical variables for all levels of hyperbolicity. Our numerical code demonstrates gravitational wave propagation in plane-symmetric spacetimes, and we compare the accuracy of the simulation by monitoring the violation of the constraints. By comparing with results obtained from the weakly hyperbolic system, we observe that the strongly and symmetric hyperbolic system show better numerical performance (yield less constraint violation), but not so much difference between the latter two. Rather, we find that the symmetric hyperbolic system is not always the best in terms of numerical performance. This study is the first to present full numerical simulations using Ashtekar's variables. We also describe our procedures in detail.