Whirling orbits around twirling black holes from conformal symmetry

Hadar, Shahar; Porfyriadis, Achilleas P.

doi:10.1007/jhep03(2017)014

Cited by 23 publications

(54 citation statements)

References 25 publications

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“…In the extremely high spin limit, conformal SL(2, R) symmetry appears in the nearhorizon limit [32][33][34][35]. Previous studies of geodesic motion in the high spin near-horizon limit were restricted either to equatorial orbits [16,[36][37][38][39][40][41] or to parametrically generic geodesics [17] that discard relevant measure-zero sets in parameter space such as the separatrix between bound and unbound motion. The first objective of this paper is to derive the complete classification of geodesics in the high spin near-horizon Kerr region.…”

Section: Introductionmentioning

confidence: 99%

Near-horizon geodesics of high spin black holes

Compère

Druart

2020

Phys. Rev. D

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We provide an exhaustive and illustrated classification of timelike and null geodesics in the near-horizon region of near-extremal Kerr black holes. The classification of polar motion extends to Kerr black holes of arbitrary spin. The classification of radial motion leads to a simple parametrization of the separatrix between bound and unbound motion. Furthermore, we prove that each timelike or null geodesic is related via conformal transformations and discrete symmetries to spherical orbits and we provide the explicit mappings. We detail the high spin behavior of both the innermost stable and the innermost bound spherical orbits.

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Section: Introductionmentioning

confidence: 99%

Near-horizon geodesics of high spin black holes

Compère

Druart

2020

Phys. Rev. D

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“…As shown in [25], these can be connected to the circular orbits by conformal transformations. Given the self-force in a seed spacetime F µ self,seed , with coordinates X µ , in which the orbit is circular and a diffeomorphism X µ (x α ) mapping this orbit to a more general geodesic in the near-horizon region, the selfforce has been conjectured to be given at leading order in the high spin limit by the tensorial transformation law induced by the coordinate transformation [21] F self,physical…”

Section: Self-forcementioning

confidence: 99%

“…Parametrically in the high spin limit, the exact result is (3.23). However in practice, the conclusion of [21] about the formula (3.1) holds since the travelling waves bring small corrections.…”

Section: An Examplementioning

confidence: 99%

“…We have investigated the scalar self-force near the horizon of a high spin black hole, at leading order in the high spin limit. We have made concrete the proposal of [21] to first compute the result for circular orbits and subsequently use the relation to more general equatorial orbits as classified in [25]. Once the self-force for circular orbits has been computed numerically, the selfforce for equatorial orbits can be deduced analytically, up to small corrections due to travelling waves.…”

Section: Summary and Prospectsmentioning

confidence: 99%

“…In this paper, we will further explore EMRIs with a central high spin black hole by making explicit and precise the suggestion of [21] to exploit the near-horizon conformal symmetry for self-force calculations at leading order in the high spin expansion. In principle, the self-force depends on the entire past of the trajectory which, due to the self-force, is non-geodesic.…”

Section: Introductionmentioning

confidence: 99%

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Scalar self-force for high spin black holes

et al. 2020

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We semi-analytically investigate the scalar self-force experienced in the final stages of extreme mass ratio inspirals of non-spinning scalar particles into supermassive nearly extremal Kerr black holes. We exploit the near-horizon conformal symmetry to find the self-force for general corotating equatorial geodesics. The angular component of the selfforce is shown to be universal at leading order in the high spin limit. We verify that the energy and angular momentum losses of the scalar particle match with the asymptotic fluxes of scalar radiation. In particular, we relate the previously described persistent oscillations in the asymptotic energy and angular momentum fluxes with the local selfforce. Such oscillations arise from travelling waves that prevent the near-horizon and the asymptotic region to fully decouple in the extremal limit. Conformal invariance is therefore reduced to discrete scale invariance with associated logarithmic periodicity.

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Is there a breakdown of effective field theory at the horizon of an extremal black hole?

Hadar

Reall

2017

J. High Energ. Phys.

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Linear perturbations of extremal black holes exhibit the Aretakis instability, in which higher derivatives of a scalar field grow polynomially with time along the event horizon. This suggests that higher derivative corrections to the classical equations of motion may become large, indicating a breakdown of effective field theory at late time on the event horizon. We investigate whether or not this happens. For extremal Reissner-Nordstrom we argue that, for a large class of theories, general covariance ensures that the higher derivative corrections to the equations of motion appear only in combinations that remain small compared to two derivative terms so effective field theory remains valid. For extremal Kerr, the situation is more complicated since backreaction of the scalar field is not understood even in the two derivative theory. Nevertheless we argue that the effects of the higher derivative terms will be small compared to the two derivative terms as long as the spacetime remains close to extremal Kerr.

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Whirling orbits around twirling black holes from conformal symmetry

Cited by 23 publications

References 25 publications

Near-horizon geodesics of high spin black holes

Near-horizon geodesics of high spin black holes

Scalar self-force for high spin black holes

Is there a breakdown of effective field theory at the horizon of an extremal black hole?

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