Black hole shadow to probe modified gravity

Степанян, А. А.; Gurzadyan, V. G.

doi:10.1140/epjp/s13360-021-01119-2

Cited by 31 publications

(11 citation statements)

References 21 publications

(15 reference statements)

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“…Figure 9 is representative, however, of a black hole with mass M, with which one can adjust the range of Λ suitably. Considering the M87* as a new Kerr-de Sitter black hole, and using the mass M = 6.5 × 10 9 M and distance d = 16.8 Mpc as reported by the Event Horizon Telescope collaboration (EHT) [85][86][87], we estimate the value of the cosmological constant Λ = 1.046 × 10 −52 m −2 , 1.368 × 10 −52 m −2 obtained, respectively, for (R s , δ s )= (4.985 × 10 13 m, 0.5) and (A, D)= (7.298 × 10 27 m 2 , 0.9812), which agree with the present estimated value of Λ = 1.11 × 10 −52 m −2 [88][89][90]. Thus, our method is robust to estimate the cosmological constant Λ as well as the spin a, provided one has a suitably chosen range for a given black hole.…”

Section: Parameter Estimation and Relative Difference Of Shadow Obser...supporting

confidence: 91%

Estimating the Cosmological Constant from Shadows of Kerr–de Sitter Black Holes

Afrin

Ghosh

2022

Universe

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The Event Horizon Telescope collaboration has revealed the first direct image of a black hole, as per the shadow of a Kerr black hole of general relativity. However, other Kerr-like rotating black holes of modified gravity theories cannot be ignored, and they are essential as they offer an arena in which these theories can be tested through astrophysical observation. This motivates us to investigate asymptotically de Sitter rotating black holes wherein interpreting the cosmological constant Λ as the vacuum energy leads to a deformation in the vicinity of a black hole—new Kerr–de Sitter solution, which has a richer geometric structure than the original one. We derive an analytical formula necessary for the shadow of the new Kerr–de Sitter black holes and then visualize the shadow of black holes for various parameters for an observer at given coordinates (r0,θ0) in the domain (r0,rc) and estimate the cosmological constant Λ from its shadow observables. The shadow observables of the new Kerr–de Sitter black holes significantly deviate from the corresponding observables of the Kerr–de Sitter black hole over an appreciable range of the parameter space. Interestingly, we find a finite parameter space for (Λ, a) where the observables of the two black holes are indistinguishable.

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Section: Parameter Estimation and Relative Difference Of Shadow Obser...supporting

confidence: 91%

Estimating the Cosmological Constant from Shadows of Kerr–de Sitter Black Holes

Afrin

Ghosh

2022

Universe

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“…For a non-Kerr rotating black hole whose null geodesic equations is integrable, the black hole shadow can also be obtained in the same way for the calculation (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) of Kerr black hole shadow. P. V. P. Cunha et al [10] studied the shadow of a Kerr black hole with Proca hair [10], and found black hole shadow has a cusp silhouette, shown in Fig.…”

Section: B Fundamental Photon Orbitsmentioning

confidence: 97%

“…For example, it is a perfect black disk for Schwarzschild black hole shadow; it gradually becomes a "D"-shaped silhouette with the increase of spin parameter for Kerr black hole shadow [8,9]; it is a cusp shadow for a Kerr black hole with Proca hair [10] and a Konoplya-Zhidenko rotating non-Kerr black hole [11]. The research of black hole shadows plays a vital role in the study of black holes (constraining black hole parameters) [12,13], probing some fundamental physics issues including dark matter [14][15][16] and verification of various gravity theories [17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Chaotic Shadows of Black Holes: A Short Review

Chen¹,

Jing²

2022

Preprint

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We give a brief review on the formation and the calculation of black hole shadow. Firstly, we introduce the conception of black hole shadow and the current works on a variety of black hole shadows. Secondly, we present main methods of calculating photon sphere radius and shadow radius, and then explain how the photon sphere affect the boundary of black hole shadow. We review the analytical calculation for black hole shadows which have analytic expressions for shadow boundary due to the integrable photon motion system. And we introduce the fundamental photon orbits which can explain the patterns of black hole shadow shape. Finally, we review the numerical calculation of black hole shadows with the backward ray-tracing method, and introduce some chaotic black hole shadows with self-similar fractal structures. Since the gravitational waves from the merger of binary black holes have been detected, we introduce a couple of shadows of binary black holes, which all have the eyebrowlike shadows around the main shadows with the fractal structures. We discuss the invariant phase space structures of photon motion system in black hole space-time, and explain the formation of black hole shadow is dominated by the invariant manifolds of certain Lyapunov orbits near the fixed points.

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“…The fourth and fifth column on the other hand are values we have computed using celestial coordinates in Ref. [1], We have chosen Λ = 1.11 × 10 −52 m −2 because cosmological tests and CMB measurements imply that this is the relevant value of the cosmological constant [27], [28], [29] TABLE II: Points evaluated for θ = 16 eq. ( 65)-( 66).…”

Section: Horizontal Diameter ∆α = (αmentioning

confidence: 99%

Remarks on the black hole shadows in Kerr-de Sitter space times

Omwoyo,

Belich,

Fabris

et al. 2021

Preprint

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This work is geared towards analysis of shadows cast by Kerr-de Sitter (KdS) and Kerr-de Sitter Revisited (RKdS) black holes. Considering observers in the vicinity of the static radius, we derive the impact parameters defining the apparent positions of the shadows. Such observers are of interest to our work because embedding diagrams have shown that de Sitter space-time is analogous to an asymptotically flat one in the vicinity of the static radius. We also perform a comparative analysis between our result with that in Ref. [1]. Furthermore, we numerically obtain the radii of curvature, vertical diameters and horizontal diameters of the shadows. We find that for Λ = 1.11 × 10 −52 m −2 , M87* observations cannot distinguish a RKdS black hole shadow from that of a Kerr black hole. Additionally, for the same value of Λ, KdS and RKdS black hole shadows are identical. Previously, it has also been shown that when Λ = 1.11 × 10 −52 m −2 , KdS and Kerr black hole shadows are indistinguishable. Utilizing the 2017 EHT observations of M87* on the allowed range of the characteristic radius of the shadow, we obtain constraints on both black holes. When, a/M > 0.812311, we observe that large angles of inclination (θ > 30.5107 • ) do not pass the constraints for both KdS and RKdS black holes.

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Black hole shadow to probe modified gravity

Cited by 31 publications

References 21 publications

Estimating the Cosmological Constant from Shadows of Kerr–de Sitter Black Holes

Estimating the Cosmological Constant from Shadows of Kerr–de Sitter Black Holes

Chaotic Shadows of Black Holes: A Short Review

Remarks on the black hole shadows in Kerr-de Sitter space times

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