The memory effect for plane gravitational waves

Zhang, P. M.; Duval, Christian; Gibbons, G. W.; Horváthy, P. A.

doi:10.1016/j.physletb.2017.07.050

Cited by 119 publications

(181 citation statements)

References 27 publications

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“…The recent review [3] could also be useful, since it emphasises some different aspects of GA in gravity, and also contains a description of some applications of GA to electromagnetism, which is only treated very briefly here (in the context of joint EM and gravitational waves). Finally, we should note for those readers interested primarily in the particular 'memory effect' for gravitational waves discussed here, that this has been independently discovered, at about the same time as the work reported here, and also related to the Brinkmann metric, by Gary Gibbons, Peter Horvathy and co-workers, and that the paper [4] would be good to consult on this, being the first in a series of papers by them on this topic.…”

Section: Introductionsupporting

confidence: 59%

“…This, and other types of memory effects, such as the 'spin memory' recently put forward by Pasterski, Strominger & Zhiboedov [23], are presumably going to be important in this 'information budget', but the precise way in which this happens is so far unclear. Returning to the question as to whether the velocity memory effect has been clearly identified before, this can certainly be answered in the context of the last two years, since shortly after I first spoke about this effect in a couple of meetings in April/May 2017, I discovered that Gary Gibbons, Peter Horvathy and coworkers had independently been looking at this, and their first full paper on this appeared later in 2017 [4]. This clearly identifies the effect discussed here, and in the eventual final version of their paper is expressed unambiguously in the Brinkmann gauge.…”

Section: Discussion and Possible Theoretical Relevance Of 'Velocity mentioning

confidence: 92%

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Geometric Algebra, Gravity and Gravitational Waves

Lasenby¹

2019

Adv. Appl. Clifford Algebras

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1 We discuss an approach to gravitational waves based on Geometric Algebra and Gauge Theory Gravity. After a brief introduction to Geometric Algebra (GA), we consider Gauge Theory Gravity, which uses symmetries expressed within the GA of flat spacetime to derive gravitational forces as the gauge forces corresponding to making these symmetries local. We then consider solutions for black holes and plane gravitational waves in this approach, noting the simplicity that GA affords in both writing the solutions, and checking some of their properties. We then go on to show that a preferred gauge emerges for gravitational plane waves, in which a 'memory effect' corresponding to non-zero velocities left after the passage of the waves becomes clear, and the physical nature of this effect is demonstrated. In a final section we present the mathematical details of the gravitational wave treatment in GA, and link it with other approaches to exact waves in the literature. Even for those not reaching it via Geometric Algebra, we recommend that the general relativity metric-based version of the preferred gauge, the Brinkmann metric, be considered for use more widely by astrophysicists and others for the study of gravitational plane waves. These advantages are shown to extend to a treatment of joint gravitational and electromagnetic plane waves, and in a final subsection, we use the exact solutions found for particle motion in exact impulsive gravitational waves to discuss whether backward in time motion can be induced by strongly non-linear waves.Mathematics Subject Classification (2010). Primary 83-XX,83C35,83C40; Secondary 83Dxx,83Cxx,15A66.

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Section: Introductionsupporting

confidence: 59%

Section: Discussion and Possible Theoretical Relevance Of 'Velocity mentioning

confidence: 92%

Geometric Algebra, Gravity and Gravitational Waves

Lasenby¹

2019

Adv. Appl. Clifford Algebras

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“…Using Eqs. (2.22) and (3.34e), we can show that 8 Note that we wrote Eq. (3.33c) in [1] in terms of a new bitensor Σ a bc .…”

Section: Observables From a Spinning Test Particlementioning

confidence: 85%

“…II C is qualitatively similar. For example, nonlinear plane wave spacetimes always have a nonzero relative velocity after a burst, often called "velocity memory" [8,11,15]. Another motivation for considering nonlinear plane wave spacetimes is as follows.…”

Section: A Simplified Model Of Geodesic Deviationmentioning

confidence: 99%

Persistent gravitational wave observables: General framework

et al. 2019

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In the first paper in this series, we introduced "persistent gravitational wave observables" as a framework for generalizing the gravitational wave memory effect. These observables are nonlocal in time and nonzero in the presence of gravitational radiation. We defined three specific examples of persistent observables: a generalization of geodesic deviation that allowed for arbitrary acceleration, a holonomy observable involving a closed curve, and an observable that can be measured using a spinning test particle. For linearized plane waves, we showed that our observables could be determined just from one, two, and three time integrals of the Riemann tensor along a central worldline, when the observers follow geodesics. In this paper, we compute these three persistent observables in nonlinear plane wave spacetimes, and we find that the fully nonlinear observables contain effects that differ qualitatively from the effects present in the observables at linear order. Many parts of these observables can be determined from two functions, the transverse Jacobi propagators, and their derivatives (for geodesic observers). These functions, at linear order in the spacetime curvature, reduce to the one, two, and three time integrals of the Riemann tensor mentioned above. CONTENTS

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“…The infinite-dimensional AS then describe the soft field dressing of a hard process, and are sensitive to the passage of charge/energy-momentum as a function of angle, through "memory" effects [21][22][23][24][25][26][27][28][29][30]. This generalization of the usual overall charge/energy-momentum conservation laws has led to the suggestion that AS charges can act as a new subtle form of "hair" that can characterize black holes (or other complex states), giving a finer understanding of black hole entropy and information puzzles [31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Asymptotic symmetries, holography and topological hair

Mishra¹,

Sundrum²

2018

J. High Energ. Phys.

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Asymptotic symmetries of AdS 4 quantum gravity and gauge theory are derived by coupling the holographically dual CFT 3 to Chern-Simons gauge theory and 3D gravity in a "probe" (large-level) limit. Despite the fact that the three-dimensional AdS 4 boundary as a whole is consistent with only finite-dimensional asymptotic symmetries, given by AdS isometries, infinite-dimensional symmetries are shown to arise in circumstances where one is restricted to boundary subspaces with effectively two-dimensional geometry. A canonical example of such a restriction occurs within the 4D subregion described by a Wheeler-DeWitt wavefunctional of AdS 4 quantum gravity. An AdS 4 analog of Minkowski "super-rotation" asymptotic symmetry is probed by 3D Einstein gravity, yielding CFT 2 structure (in a large central charge limit), via AdS 3 foliation of AdS 4 and the AdS 3 /CFT 2 correspondence. The maximal asymptotic symmetry is however probed by 3D conformal gravity. Both 3D gravities have Chern-Simons formulation, manifesting their topological character. Chern-Simons structure is also shown to be emergent in the Poincare patch of AdS 4 , as soft/boundary limits of 4D gauge theory, rather than "put in by hand" as an external probe. This results in a finite effective Chern-Simons level. Several of the considerations of asymptotic symmetry structure are found to be simpler for AdS 4 than for Mink 4 , such as non-zero 4D particle masses, 4D non-perturbative "hard" effects, and consistency with unitarity. The last of these in particular is greatly simplified because in some setups the time dimension is explicitly shared by each level of description: Lorentzian AdS 4 , CFT 3 and CFT 2 . Relatedly, the CFT 2 structure clarifies the sense in which the infinite asymptotic charges constitute a useful form of "hair" for black holes and other complex 4D states. An AdS 4 analog of Minkowski "memory" effects is derived, but with late-time memory of earlier events being replaced by (holographic) "shadow" effects. Lessons from AdS 4 provide hints for better understanding Minkowski asymptotic symmetries, the 3D structure of its soft limits, and Minkowski holography.

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The memory effect for plane gravitational waves

Cited by 119 publications

References 27 publications

Geometric Algebra, Gravity and Gravitational Waves

Geometric Algebra, Gravity and Gravitational Waves

Persistent gravitational wave observables: General framework

Asymptotic symmetries, holography and topological hair

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