Speaker
Description
The initial-boundary value problem in general relativity has been the subject of extensive study. A central issue is the identification of boundary data and conditions on timelike boundaries that ensure well-posedness. In the work presented here, we approach the problem by considering perturbations of a background metric. We seek to disentangle the modes present in these perturbations, distinguishing between physical modes, those associated with gauge freedom, and those arising from constraints. This perspective clarifies how gauge conditions and constraints restrict the admissible boundary data. In particular, it explains why Dirichlet boundary conditions are generally ill posed, helps identify viable alternative choices of boundary data, and specifies the additional conditions required for their numerical implementation.