Extensions of the asymptotic symmetry algebra of general relativity

Flanagan, Éanna É.; Prabhu, Kartik; Shehzad, Ibrahim

doi:10.1007/jhep01(2020)002

Cited by 46 publications

(63 citation statements)

References 39 publications

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“…covariant as noted in [101], the procedure used here is explicitly covariant (in terms of the boundary structure) and therefore justifies a posteriori the counterterm prescription for subtracting a radial divergence used in [9]. We find curious that the radially diverging term encountered in [9] (see equations (5.18) and (5.19)) is structurally similar to the Λ → 0 diverging term found here (4.13).…”

Section: Jhep10(2020)205supporting

confidence: 68%

The Λ-BMS4 charge algebra

Compère

Fiorucci

Ruzziconi

2020

J. High Energ. Phys.

120

206

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The surface charge algebra of generic asymptotically locally (A)dS4 spacetimes without matter is derived without assuming any boundary conditions. Surface charges associated with Weyl rescalings are vanishing while the boundary diffeomorphism charge algebra is non-trivially represented without central extension. The Λ-BMS4 charge algebra is obtained after specifying a boundary foliation and a boundary measure. The existence of the flat limit requires the addition of corner terms in the action and symplectic structure that are defined from the boundary foliation and measure. The flat limit then reproduces the BMS4 charge algebra of supertranslations and super-Lorentz transformations acting on asymptotically locally flat spacetimes. The BMS4 surface charges represent the BMS4 algebra without central extension at the corners of null infinity under the standard Dirac bracket, which implies that the BMS4 flux algebra admits no non-trivial central extension.

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Section: Jhep10(2020)205supporting

confidence: 68%

The Λ-BMS4 charge algebra

Compère

Fiorucci

Ruzziconi

2020

J. High Energ. Phys.

120

206

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“…Additionally, finite, integrable charges must be constructed that generate the action of Diff(S 2 ) on this phase space. See [8,30] for recent work on this front. We leave investigation into such a symplectic form to future work.…”

Section: Relaxing Fixed-metric Boundary Conditionsmentioning

confidence: 99%

Cosmic footballs from superrotations

Adjei

Donnelly

et al. 2020

Class. Quantum Grav.

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Superrotations arise from singular vector fields on the celestial sphere in asymptotically flat space, and their finite integrated versions have been argued by Strominger and Zhiboedov to insert cosmic strings into the spacetime. In this work, we argue for an alternative definition of the action of superrotations on Minkowski space that avoids introducing any defects. This involves realizing the finite superrotation not as a diffeomorphism between spaces, but as a mapping of Minkowski space to itself that may be multivalued or non-surjective. This eliminates any defects in the bulk spacetime at the expense of allowing for defects in the boundary celestial sphere metric. We further explore the geometry of the spatial surfaces in the superrotated spaces, and note that they intersect null infinity at the singularity of the superrotation, causing a breakdown in the large r asymptotic expansion there. To determine how these surfaces embed into Minkowski space, a derivation of the finite superrotation transformation is presented in both Bondi and Newman-Unti gauges. The latter is particularly interesting, since the superrotations are shown to preserve the hyperbolic slicing of Minkowski space in Newman-Unti gauge, and this gauge also provides a means for extending the geometry beyond the Bondi coordinate patch. We argue that the new interpretation for the action of superrotations on spacetime motivates consideration of a wider class of celestial sphere metrics and asymptotic symmetry groups. Conical defect in the finite superrotationSuperrotations were proposed in [4,7] as an infinite-dimensional extension of the asymptotic symmetry group of asymptotically flat general relativity. They arise as generalizations of Lorentz transformations, and are characterized by their action on the celestial 2-sphere. The Lorentz group acts as the global conformal isometry group of the celestial sphere, while the superrotations act as local conformal isometries, which may not be globally defined due to singular points.

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“…These equations can be readily solved and the solutions are given by where Diff(S 2 ) are the smooth superrotations generated by Y A and S are the smooth supertranslations generated by T . This extension of the original global BMS 4 algebra (see below) is called the generalized BMS 4 algebra [67][68][69][70]. Therefore, the Λ-BMS 4 algebra reduces in the flat limit to the smooth extension (3.69) of the BMS 4 algebra.…”

Section: Asymptotic Symmetry Algebramentioning

confidence: 99%

Asymptotic Symmetries in the Gauge fixing Approach and the BMS group

Ruzziconi¹

2020

Proceedings of XV Modave Summer School in Mathematical Physics — PoS(Modave2019)

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These notes are an introduction to asymptotic symmetries in gauge theories, with a focus on general relativity in four dimensions. We explain how to impose consistent sets of boundary conditions in the gauge fixing approach and how to derive the asymptotic symmetry parameters. The different procedures to obtain the associated charges are presented. As an illustration of these general concepts, the examples of fourdimensional general relativity in asymptotically (locally) (A)dS 4 and asymptotically flat spacetimes are covered. This enables us to discuss the different extensions of the Bondi-Metzner-Sachs-van der Burg (BMS) group and their relevance for holography, soft gravitons theorems, memory effects, and black hole information paradox. These notes are based on lectures given at the XV Modave Summer School in Mathematical Physics.

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Extensions of the asymptotic symmetry algebra of general relativity

Cited by 46 publications

References 39 publications

The Λ-BMS4 charge algebra

The Λ-BMS4 charge algebra

Cosmic footballs from superrotations

Asymptotic Symmetries in the Gauge fixing Approach and the BMS group

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