Angular momentum in general relativity: The definition at null infinity includes the spatial definition as a special case

摘要

I show that the definition of angular momentum at null infinity given by A. Rizzi, Phys. Rev. Lett. 81, 1150 (1998), reduces to the Arnowitt-Deser-Misner definition at spatial infinity in the appropriate limit. This identification reinforces the gauge condition of the null definition as well as the null definition itself. Insight into the place of the null and spatial definitions is also gained. The methods used in this paper are very useful for understanding far-field problems in general relativity; a set of Appendixes gives details of the methods.