Vacua of the gravitational field

Compère, Geoffrey; Long, Jiang

doi:10.1007/jhep07(2016)137

Cited by 116 publications

(187 citation statements)

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“…This requirement formally amounts to the existence of a phase space with symplectic symmetries, which extends the concept of asymptotic symmetries into the bulk [11-13] (see also [14]). The supertranslation field is then promoted to a bulk concept, characterized by its conserved charges.Both static radial gauge and BMS gauge lead to such a phase space for the vacua [15]. The metric can be built explicitly and reads in static radial gauge as…”

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confidence: 99%

Bulk supertranslation memories: A concept reshaping the vacua and black holes of general relativity

Compère

2016

Int. J. Mod. Phys. D

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The memory effect is a prediction of general relativity on the same footing as the existence of gravitational waves. The memory effect is understood at future null infinity as a transition induced by null radiation from a Poincaré vacuum to another vacuum. Those are related by a supertranslation, which is a fundamental symmetry of asymptotically flat spacetimes. In this essay, I argue that finite supertranslation diffeomorphisms should be extended into the bulk spacetime consistently with canonical charge conservation. It then leads to fascinating geometrical features of gravitational Poincaré vacua. I then argue that in the process of black hole merger or gravitational collapse, dramatic but computable memory effects occur. They lead to a final stationary metric which qualitatively deviates from the Schwarzschild metric.Essay written for the Gravity Research Foundation 2016 Awards for Essays on Gravitation. Honorable mention. arXiv:1606.00377v1 [hep-th] 1 Jun 2016What is gravity? In general relativity, the gravitational field is the metric field. It contains the Newtonian potential corrected by relativistic effets, which leads to gravitational attraction, the bending of light and many other well-known gravitational phenomena. The metric also describes gravitational waves, a spin 2 field best isolated in linearized Einstein gravity, which couples to the Newtonian field at the non-linear level. Finally, the metric also contains a third physically distinct component: the supertranslation memory field, originally defined close to future null infinity. This field is intimately coupled to gravitational waves but is related to a physically distinct effect: the memory effect [1,2]. I will argue that the supertranslation memory field leads to new phenomena when considered in the bulk spacetime. Gravitational memoryAfter the passage of either gravitational waves or null matter between two detectors placed in the asymptotic null region, the detectors generically acquire a finite relative spatial displacement and a finite time shift. This is the memory effect, respectively non-linear for gravitational waves and linear for null matter [1,2]. Since this displacement is a zero frequency effect, it cannot straightforwardly be detected by ground-based interferometers such as LIGO mainly because of seismic noise which blurs the signal at low frequencies < 30Hz. Nevertheless, sophisticated data analyses might make such a measurement possible in the future [3].Memory effects do not exist in Newtonian gravity. In Einstein gravity, they naturally arise in post-Newtonian wave forms created by an inspiraling binary system. Such wave forms depend upon the entire past history of the system [4]. These "hereditary effects" can be identified as the tail effect and the non-linear memory effect [5]. The tail effect first appears at 1.5PN order and is attributed to backscattering of past gravitational waves. It will not concern us here. The nonlinear memory effect first appears at 2.5PN order and gives rise to a net cumulative change ...

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confidence: 99%

Bulk supertranslation memories: A concept reshaping the vacua and black holes of general relativity

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2016

Int. J. Mod. Phys. D

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“…With this identification, both the metric (55) in advanced coordinates and the metric (56) in retarded coordinates cover the whole manifold. Extrapolating the results of [20,21], where finite supertranslations of Schwarzschild and Minkowski are discussed, we expect that for any other matching, i.e. for any other value of the supertranslation field, this is no longer the case.…”

Section: Explicit Solution For Goldstone Supertranslation Of a Planetmentioning

confidence: 80%

“…As is shown explicitly in Appendix B for the example of the Schwarzschild metric, we can achieve this by identifying C + (θ, ϕ) = −C − (θ, ϕ), as also proposed in [20]. Up to a sign, we match the supertranslation field angle-wise.…”

Section: Coordinate Matchingmentioning

confidence: 92%

“…This approach has received widespread attention (see e.g. [13][14][15][16][17][18][19][20][21][22][23][24]). In particular, a potential new form of classical hair for a black hole has been proposed [25,26].…”

Section: Classical Bms-hairmentioning

confidence: 99%

“…More generically, it is possible to require that the action of advanced and retarded supertranslations is the same in the bulk. This was done in [20,21] for the cases of Schwarzschild and Minkowski.…”

Section: Coordinate Matchingmentioning

confidence: 99%

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Black hole evaporation, quantum hair and supertranslations

Gómez

Zell

2018

Eur. Phys. J. C

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In a black hole, hair and quantum information retrieval are interrelated phenomena. The existence of any new form of hair necessarily implies the existence of features in the quantum-mechanically evaporated radiation. Therefore, classical supertranslation hair can be only distinguished from global diffeomorphisms if we have access to the interior of the black hole. Indirect information on the interior can only be obtained from the features of the quantum evaporation. We demonstrate that supertranslations (T − , T + ) ∈ B M S − ⊗ B M S + can be used as bookkeepers of the probability distributions of the emitted quanta where the first element describes the classical injection of energy and the second one is associated to quantum-mechanical emission. However, the connection between T − and T + is determined by the interior quantum dynamics of the black hole. We argue that restricting to the diagonal subgroup is only possible for decoupled modes, which do not bring any non-trivial information about the black hole interior and therefore do not constitute physical hair. It is shown that this is also true for gravitational systems without horizon, for which both injection and emission can be described classically. Moreover, we discuss and clarify the role of infrared physics in purification.

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Asymptotically Flat Spacetimes

Compère

2019

Advanced Lectures on General Relativity

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Vacua of the gravitational field

Cited by 116 publications

References 60 publications

Bulk supertranslation memories: A concept reshaping the vacua and black holes of general relativity

Bulk supertranslation memories: A concept reshaping the vacua and black holes of general relativity

Black hole evaporation, quantum hair and supertranslations

Asymptotically Flat Spacetimes

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