Erratum: Near-horizon geodesics of high spin black holes [Phys. Rev. D 
<b>101</b>
, 084042 (2020)]

Compère, Geoffrey; Druart, Adrien

doi:10.1103/physrevd.102.029901

Cited by 7 publications

(10 citation statements)

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“…The size of a stationary black hole is closely connected with its photon region, which is the set of all radially unstable bound photon orbits [15][16][17][18][19][20][21][22][23][24]. Among them, circular photon orbits are called light rings.…”

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confidence: 99%

Universal Properties of Light Rings for Stationary Axisymmetric Spacetimes

Guo,

Gao

2020

Preprint

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Light rings (LRs) play an important role in gravitational wave observations and black hole photographs. In this letter, we investigate general features of LRs in stationary, axisymmetric, asymptotically flat spacetimes with or without horizons. For a nonextremal black hole, we show explicitly that there always exist at least two LRs propagating in opposite directions, where the outermost one is radially unstable. For an extremal black hole, we show that there exists at least one retrograde LR. Our method also applies to horizonless spacetimes and we prove that LRs always appear in pairs. We also show that there exists at least one LR which is angularly stable. The stability analysis do not involve any energy condition. Only some natural and generic assumptions are used in our proof. The results are applicable to general relativity as well as most modified theories of gravity. In contrast to previous works on this issue, we obtain much stronger results with a much more straightforward approach.

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confidence: 99%

Universal Properties of Light Rings for Stationary Axisymmetric Spacetimes

Guo,

Gao

2020

Preprint

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“…As is demonstrated above, the particle's energy E, angular momentum L and rest mass are three constants of motion in the system (39). Does a fourth constant exist?…”

Section: A Integrability Of the System (39) Without Cosmological Cons...mentioning

confidence: 91%

“…Firstly, we discuss the integrability of the Hamiltonian system (39) with a vanishing cosmological constant by finding a fourth integral of motion in this system. Secondly, physically allowed motion regions are analyzed.…”

Section: Integrable Dynamics Of Charged Particlesmentioning

confidence: 99%

“…The threshold spherical photon orbits mark a boundary between the photons captured by the black hole and the photons escaping to infinity. Therefore, there have been many other papers focusing on these spherical photon orbits (see, e.g., [37][38][39]).…”

Section: Introductionmentioning

confidence: 99%

“…Stable spherical charged-particle orbits are also present. Unlike the authors who studied the spherical photon orbits in the literature [37][38][39], we mainly focus on the stable circular charged-particle orbits in two-dimensional nonequatorial planes and the stable spherical charged-particle orbits. They are important in an astrophysical scenario.…”

Section: Introductionmentioning

confidence: 99%

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Integrability of Kerr-Newman spacetime with cloud strings, quintessence and electromagnetic field

Cao,

Liu,

2022

Preprint

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The dynamics of charged particles moving around a Kerr-Newman black hole surrounded by cloud strings, quintessence and electromagnetic field is integrable due to the presence of a fourth constant of motion like the Carter constant. The fourth motion constant and the axial-symmetry of the spacetime give a chance to the existence of radial effective potentials with stable circular orbits in two-dimensional planes, such as the equatorial plane and other nonequatorial planes. They also give a possibility of the presence of radial effective potentials with stable spherical orbits in the three-dimensional space. The dynamical parameters play important roles in changing the graphs of the effective potentials. In addition, variations of these parameters affect the presence or absence of stable circular orbits, innermost stable circular orbits, stable spherical orbits and marginally stable spherical orbits. They also affect the radii of the stable circular or spherical orbits. It is numerically shown that the stable circular orbits and innermost stable circular orbits can exist not only in the equatorial plane but also in the nonequatorial planes. Several stable spherical orbits and marginally stable spherical orbits are numerically confirmed, too. In particular, there are some stable spherical orbits and marginally stable spherical orbits with vanishing angular momenta for covering whole the range of the latitudinal coordinate.

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Photon boomerang in a nearly extreme Kerr metric

Page

2022

Class. Quantum Grav.

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The Kerr rotating black hole metric has unstable photon orbits that orbit around the hole at ﬁxed values of the Boyer-Lindquist coordinate r that depend on the axial angular momentum of the orbit, as well as on the parameters of the hole. For zero orbital axial angular momentum, these orbits cross the rotational axes at a ﬁxed value of r that depends on the mass M and angular momentum J of the black hole. Nonzero angular momentum of the hole causes the photon orbit to rotate so that its direction when crossing the north polar axis changes from one crossing to the next by an angle I shall call ∆φ, which depends on the black hole dimensionless rotation parameter a/M = cJ/(GM2) by an equation involving a complete elliptic integral of the ﬁrst kind. When the black hole has a/M ≈ 0.994 341 179 923 26, which is nearly maximally rotating, a photon sent out in a constant-r direction from the north polar axis at r ≈ 2.423 776 210 035 73 GM/c2returns to the north polar axis in precisely the opposite direction (in a frame nonrotating with respect to the distant stars), a photon boomerang.

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Erratum: Near-horizon geodesics of high spin black holes [Phys. Rev. D 101 , 084042 (2020)]

Cited by 7 publications

References 0 publications

Universal Properties of Light Rings for Stationary Axisymmetric Spacetimes

Universal Properties of Light Rings for Stationary Axisymmetric Spacetimes

Integrability of Kerr-Newman spacetime with cloud strings, quintessence and electromagnetic field

Photon boomerang in a nearly extreme Kerr metric

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