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Angular momentum at null infinity. (English) Zbl 1136.83316
Summary: The definition of angular momentum recently given by R. Penrose [Proc. R. Soc. Lond. Ser. A 381, No. 1780, 53–63 (1982)] is analysed on I. It is shown that this definition is essentially a supertranslation of previous definitions [for example, the one by Streubel in Gen. Relativity Gravitation 9, No. 6, 551–561 (1978)]. The origin dependence of Penrose’s angular momentum is shown to have the correct form. Based on Penrose’s expression, the authors then define a momentum for all elements of the BMS Lie algebra, which is the first such expression with the property that its flux vanishes identically in Minkowski space.

MSC:
83C30Asymptotic procedures (general relativity)
83C40Gravitational energy and conservation laws; groups of motions