Supercentre of mass system at future null infinity

Abstract

This paper investigates the possibility of eliminating the supertranslation gauge freedom at scri by the introduction of a unique set of sections, which may be understood as giving a centre of mass system of reference. The construction depends on the properties of the physical system at the fixed retarded time defined by these sections.

Erratum: Observer dependence of angular momentum in general relativity and its relationship to the gravitational-wave memory effect [Phys. Rev. D92, 084057 (2015)]

“…Some researchers have argued that it is necessary or desirable to give a definition of a preferred finite set of conserved charges, that would be more similar to the familiar conserved charges of special relativity [9][10][11][12][13]. An alternative philosophy, which we espouse, is that all of the BMS charges are physically relevant and that one should try to understand more deeply their physical nature, starting with operational prescriptions by which they can be measured by asymptotic observers.…”

“…11 Note that the parameter τ need not be the proper time along B's worldline, and the orthonormal tetrad fα need not be parallel transported along B's worldline.…”

Perturbations with angular momentum of Robinson-Trautman spacetimes

“…If ℑmJ where zero then one can see that a transformation of the form u = u − γ(ζ,ζ) would do the job. It is conceivable that for small time variations one can use techniques similar to those of references [11] and [14] to prove local existence of transformations that make ℑmJ = 0.…”

Comment on “Boosted Kerr black holes in general relativity”

“…there exists a canonical way to set a preferred Poincare subgroup based in the notion of good cuts [17] or its generalization through nice sections [18]. Since a boost in Special Relativity is done with respect to observers in inertial frames, it is clear that an asymptotic boost in an asymptotically flat spacetime ought be done a with respect to an associated Bondi frames.…”