Boundary Conditions for the Gravitational Field

Understand

A review of the treatment of boundaries in general relativity is presented with the emphasis on application to the formulations of Einstein's equations used in numerical relativity.

• At present, it is known how to treat boundaries in the harmonic formulation of Einstein's equations and a tetrad formulation of the Einstein-Bianchi system.
• However, a universal approach valid for other formulations is not in hand.
• In particular, there is no satisfactory boundary theory for the 3+1 formulations which have been highly successful in binary black hole simulation.