Linkages in general relativity

TLDR: In this article, the ambiguities due to the possible presence of supertranslations in asymptotic rotations are studied using the behavior of the linkages under first-order perturbations in the metric.

Abstract: For an asymptotically flat space–time in general relativity there exist certain integrals, called linkages, over cross sections of null infinity, which represent the energy, momentum, or angular momentum of the system. A new formulation of the linkages is introduced and applied. It is shown that there exists a flux, representing the contribution of gravitational and matter radiation to the linkage. A uniqueness conjecture for the linkages is formulated. The ambiguities due to the possible presence of supertranslations in asymptotic rotations are studied using the behavior of the linkages under first‐order perturbations in the metric. While in certain situations these ambiguities disappear in the first‐order treatment, an example is given which suggests that they are an essential feature of general relativity and its asymptotic structure.