Shadow of a disformal Kerr black hole in quadratic degenerate higher-order scalar–tensor theories

Long, Fen; Chen, Songbai; Jing, Jiliang

doi:10.1140/epjc/s10052-020-08744-8

Cited by 47 publications

(34 citation statements)

References 48 publications

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“…The cusp silhouette of black hole shadows emerge in the spacetime of a Kerr black hole with Proca hair and a Konoplya-Zhidenko rotating non-Kerr black hole [10,11]. The eyebrow-like shadow and the self-similar fractal structures appear in the shadow for the disformal Kerr black hole in quadratic degenerate higher-order scalar-tensor theory [12]. In dS or AdS spacetimes, the size and shape of black hole shadow are related to the cosmological constant and the position of comoving observer [13][14][15][16].…”

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confidence: 96%

Kerr Black hole shadows in Melvin magnetic field with stable photon orbits

Wang,

Chen,

Jing

2021

Preprint

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We have studied the shadows of black hole immersed in Melvin magnetic field. Due to the existence of Melvin magnetic field, the shadow of Melvin-Schwarzschild black hole becomes more elongated in the horizontal direction so that the black silhouette changes from a perfect circle to an ellipse.We also present the change of the eccentricity for the ellipse-shaped shadow with the magnetic field parameter. For a rotating black hole, with the increasing of the rotation parameter, the ellipse-shaped shadow becomes gradually a D-shaped silhouette elongated in the horizontal direction.Moreover, the right part of the D-shaped and elongated shadow boundary can be matched very well by a part of an ellipse, and the corresponding eccentricity decreases with the rotation parameter and increases with the magnetic field parameter. In addition, there also exist some self-similar fractal structures in the shadow of Melvin-Kerr black hole arising from the chaotic motion of photon. These behavior of shadow of Melvin-Kerr black hole can help us to understand the black hole shadow and the magnetic field around black hole.

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confidence: 96%

Kerr Black hole shadows in Melvin magnetic field with stable photon orbits

Wang,

Chen,

Jing

2021

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“…Now, we study the shadows of Schwarzschild black hole with halos through the backward ray-tracing technique [12][13][14][15][16][17][18][19][20][21][22][23][24] by solving numerically the null geodesic equations ( 11) and (12). We assume that the static observer is locally at (r obs , θ obs ) in zero-angular-moment-observers (ZAMOs) reference frame [8], and evolved light rays from the observer backward in time.…”

Section: The Shadows Casted By Schwarzschild Black Hole With Halosmentioning

confidence: 99%

“…The shadow of black hole is composed by the light rays falling down into the event horizon of black hole. The coordinates of a photon's image in observer's sky can be expressed as [12][13][14][15][16][17][18][19][20][21][22][23][24] x = −r obs 1…”

Section: The Shadows Casted By Schwarzschild Black Hole With Halosmentioning

confidence: 99%

The surface geometry and shadow of a Schwarzschild black hole with halo

Guo¹,

Chen²,

Jing³

2021

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We have studied the shadows of Schwarzschild black hole with a halo containing quadrupolar and octopolar terms. We found black hole shadow is oblate when the quadrupole strength Q is greater than zero, and it is prolate when Q is less than zero. Black hole shadow shifts upward when the octopolar strength O is less than zero, and shifts downward when O is greater than zero. From the observable width W , height H, oblateness K and distortion parameter δ of black hole shadow, one can determine the quadrupole strength Q and octopolar strength O of Schwarzschild black hole with halo. Black hole shadow is always a circle for the observers with the inclination angle θ obs = 0, and becomes bigger with the increase of Q or O. Black hole shadow not only becomes more prolate but also shifts upward as the quadrupole strength Q increases for the observer inclination angle θ obs = π/4. But black hole shadow shifts upward as O increases for θ obs = π/4, which is the opposite of the case of θ obs = π/2. Our results show that the quadrupolar and octopolar terms yield a series of interesting patterns for the shadow of a Schwarzschild black hole with halo.

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“…*2 Also, the quadratic/cubic DHOST class itself is closed under the disformal transformation [10]. Applications of the disformal transformation have been extensively explored in various contexts; inflation [32][33][34][35][36], cosmic microwave background [37][38][39], dark matter and dark energy [40][41][42][43][44][45][46], cosmological perturbations [47][48][49][50][51][52][53][54], solar system tests and screening mechanisms [41,[55][56][57][58][59], relativistic stars [60][61][62][63], and black holes [64][65][66][67][68][69][70][71][72][73][74][75][76][77].…”

Section: Introductionmentioning

confidence: 99%

Invertible disformal transformations with higher derivatives

Takahashi,

Motohashi,

Minamitsuji

2021

Preprint

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We consider a higher-derivative generalization of disformal transformations and clarify the conditions under which they form a group with respect to the matrix product and the functional composition. These conditions allow us to systematically construct the inverse transformation in a fully covariant manner. Applying the invertible generalized disformal transformation to known ghost-free scalar-tensor theories, we obtain a novel class of ghost-free scalar-tensor theories, whose action contains the third-or higher-order derivatives of the scalar field as well as nontrivial higherorder derivative couplings to the curvature tensor.*1 Relaxing the degeneracy conditions so that the higher-derivative terms are degenerate only in the unitary gauge, we obtain a broader class of scalar-tensor theories [13][14][15][16][17]. In that case, there is an apparent extra DOF in a generic gauge, but it satisfies an elliptic differential equation and hence is an instantaneous (or "shadowy") mode [14,17]. *2 However, in two spacetime dimensions, the Horndeski class is closed under the disformal transformation of the form (1) [31].

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Shadow of a disformal Kerr black hole in quadratic degenerate higher-order scalar–tensor theories

Cited by 47 publications

References 48 publications

Kerr Black hole shadows in Melvin magnetic field with stable photon orbits

Kerr Black hole shadows in Melvin magnetic field with stable photon orbits

The surface geometry and shadow of a Schwarzschild black hole with halo

Invertible disformal transformations with higher derivatives

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