Gravitational lensing, memory, and the Penrose limit

Frolov, Valeri P.; Koek, Alex

doi:10.1103/physrevd.106.064026

Cited by 2 publications

(7 citation statements)

References 36 publications

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“…As in the parallel case, this also agrees with results in the literature for the ultraboost of Kerr orthogonal to the axis of rotation [21,23,54].…”

Section: Jhep02(2023)107supporting

confidence: 91%

“…That is, just because the Born approximation is not totally physical doesn't mean that it cannot encode some of the classical spin effects associated with Kerr (cf., [53,[96][97][98][99][100][101][102]). By analogy, we saw that the ultraboost of Kerr orthogonal to the axis of rotation did not contain true spin effects, but a naive replacement rule nevertheless correctly reproduces the bending of light in the Kerr metric [54,55].…”

Section: Discussionmentioning

confidence: 92%

“…There is a natural generalization beyond the class of metrics we considered which could better capture the ultrarelativistic limit of the Kerr metric. The set of 'impulsive gyraton' metrics inside of the pp-wave class has three (rather than one) functional degrees of freedom JHEP02(2023)107 in D = 4, and these certainly encode internal angular momentum [54,[103][104][105][106]. Thus, it could be that a richer candidate for the ultrarelativistic limit of Kerr can be found in this impulsive gyraton class, although the straightforward relationship between the metric and on-shell scattering amplitudes that was utilized here would need to be modified.…”

Section: Discussionmentioning

confidence: 99%

“…This can be accomplished by demanding that the ring radius a µ remains constant; while this may seem un-natural (indeed, it means the spin tensor vanishes in the massless limit), it can be interpreted as saying that the correct spin information is encoded in the massless limit in the finite vector a µ . Something similar is done in gluing constructions of spinning null metrics which keep a finite ring radius with vanishing angular momentum [54].…”

Section: Jhep02(2023)107mentioning

confidence: 99%

“…Despite this, it is curious to note that the bending of light in Kerr can be derived by a simple replacement P− → M . See[54] and[55] for more on this point 5. We have normalized the lightfront energy of the solution with a factor of 2 relative to[26].…”

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confidence: 99%

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The ultrarelativistic limit of Kerr

Adamo

Cristofoli

Tourkine

2023

J. High Energ. Phys.

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The massless (or ultrarelativistic) limit of a Schwarzschild black hole with fixed energy was determined long ago in the form of the Aichelburg-Sexl shockwave, but the status of the same limit for a Kerr black hole is less clear. In this paper, we explore the ultrarelativistic limit of Kerr in the class of Kerr-Schild impulsive pp-waves by exploiting a relation between the metric profile and the eikonal phase associated with scattering between a scalar and the source of the metric. This gives a map between candidate metrics and tree-level, 4-point scattering amplitudes. At large distances from the source, we find that all candidates for the massless limit of Kerr in this class do not have spin effects. This includes the metric corresponding to the massless limit of the amplitude for gravitational scattering between a scalar and a massive particle of infinite spin. One metric, discovered by Balasin and Nachbagauer, does have spin and finite size effects at short distances, leading to a remarkably compact scattering amplitude with many interesting properties. We also discuss the classical single copy of the ultrarelativistic limit of Kerr in electromagnetism.

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“…As in the parallel case, this also agrees with results in the literature for the ultraboost of Kerr orthogonal to the axis of rotation [21,23,54].…”

Section: Jhep02(2023)107supporting

confidence: 91%

Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Jhep02(2023)107mentioning

confidence: 99%

mentioning

confidence: 99%

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The ultrarelativistic limit of Kerr

Adamo

Cristofoli

Tourkine

2023

J. High Energ. Phys.

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Electric shocks: bounding Einstein-Maxwell theory with time delays on boosted RN backgrounds

Cremonini,

McPeak,

Tang

2024

J. High Energ. Phys.

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The requirement that particles propagate causally on non-trivial backgrounds implies interesting constraints on higher-derivative operators. This work is part of a systematic study of the positivity bounds derivable from time delays on shockwave backgrounds. First, we discuss shockwaves in field theory, which are infinitely boosted Coulomb-like field configurations. We show how a positive time delay implies positivity of four-derivative operators in scalar field theory and electromagnetism, consistent with the results derived using dispersion relations, and we comment on how additional higher-derivative operators could be included.We then turn to gravitational shockwave backgrounds. We compute the infinite boost limit of Reissner-Nordström black holes to derive charged shockwave backgrounds. We consider photons traveling on these backgrounds and interacting through four-derivative corrections to Einstein-Maxwell theory. The inclusion of gravity introduces a logarithmic term into the time delay that interferes with the straightforward bounds derivable in pure field theory, a fact consistent with CEMZ and with recent results from dispersion relations. We discuss two ways to extract a physically meaningful quantity from the logarithmic time delay — by introducing an IR cutoff, or by considering the derivative of the time delay — and comment on the bounds implied in each case. Finally, we review a number of additional shockwave backgrounds which might be of use in future applications, including spinning shockwaves, those in higher dimensions or with a cosmological constant, and shockwaves from boosted extended objects.

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Gravitational lensing, memory, and the Penrose limit

Cited by 2 publications

References 36 publications

The ultrarelativistic limit of Kerr

The ultrarelativistic limit of Kerr

Electric shocks: bounding Einstein-Maxwell theory with time delays on boosted RN backgrounds

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