A novel test of gravity via black hole eikonal correspondence

Chen, Che-Yu; Chen, Yu-Jui; Ho, Meng-Yuan; Tseng, Yung-Hsuan

doi:10.48550/arxiv.2212.10028

Cited by 2 publications

(2 citation statements)

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“…In this case, the use of techniques based on orbital angular momentum and twisted light in the vicinity of the BH appears promising, although for Sgr A * the use of these techniques may be challenging due to its very short dynamical timescale [85,1555,1556]. In closing, we further note that VLBI images allow for a wide variety of tests of fundamental physics beyond those we have considered here, including but not limited to tests of the equivalence principle based on multi-frequency images [105], to probes of ultra-light particles and other aspects of fundamental physics based on shadow evolution [92,150,159,169], spin measurements [1557], and polarimetric measurements [1558,1559], and various tests of fundamental physics based on the BH photon ring, its auto-correlation, and other probes [40,169,[1560][1561][1562][1563][1564]. Studies on these and related possibilities are underway, and we expect to report on these in future works.…”

Section: Modelmentioning

confidence: 99%

Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗

Vagnozzi

Roy

Tsai

et al. 2023

Class. Quantum Grav.

280

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Horizon-scale images of black holes (BHs) and their shadows have opened an unprecedented window onto tests of gravity and fundamental physics in the strong-field regime. We consider a wide range of well-motivated deviations from classical General Relativity (GR) BH solutions, and constrain them using the Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), connecting the size of the bright ring of emission to that of the underlying BH shadow and exploiting high-precision measurements of Sgr A*’s mass-to-distance ratio. The scenarios we consider, and whose fundamental parameters we constrain, include various regular BHs, string-inspired space-times, violations of the no-hair theorem driven by additional fields, alternative theories of gravity, novel fundamental physics frameworks, and BH mimickers including well-motivated wormhole and naked singularity space-times. We demonstrate that the EHT image of Sgr A* places particularly stringent constraints on models predicting a shadow size larger than that of a Schwarzschild BH of a given mass, with the resulting limits in some cases surpassing cosmological ones. Our results are among the first tests of fundamental physics from the shadow of Sgr A* and, while the latter appears to be in excellent agreement with the predictions of GR, we have shown that a number of well-motivated alternative scenarios, including BH mimickers, are far from being ruled out at present.

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Section: Modelmentioning

confidence: 99%

Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗

Vagnozzi

Roy

Tsai

et al. 2023

Class. Quantum Grav.

280

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“…The breaking of the eikonal correspondence has been found in some modified theories of gravity, such as those with nonminimal matter-gravity couplings [89][90][91][92] or those with higher spacetime dimensions [93,94]. Therefore, observationally testing the correspondence could be a potential way of searching physics beyond GR [95].…”

Section: Jcap07(2024)022mentioning

confidence: 99%

Linear stability of vector Horndeski black holes

Chen,

Felice,

Tsujikawa

2024

J. Cosmol. Astropart. Phys.

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Horndeski's vector-tensor (HVT) gravity is described by a Lagrangian in which the field strength fμν = ∂μAν-∂νAμ of a vector field Aμ interacts with a double dual Riemann tensor Lμναβ in the form βLμναβ Fμν Fαβ , where β is a constant. In Einstein-Maxwell-HVT theory, there are static and spherically symmetric black hole (BH) solutions with electric or magnetic charges, whose metric components are modified from those in the Reissner-Nordström geometry. The electric-magnetic duality of solutions is broken even at the background level by the nonvanishing coupling constant β. We compute a second-order action of BH perturbations containing both the odd- and even-parity modes and show that there are four dynamical perturbations arising from the gravitational and vector-field sectors. We derive all the linear stability conditions associated with the absence of ghosts and radial/angular Laplacian instabilities for both the electric and magnetic BHs. These conditions exhibit the difference between the electrically and magnetically charged cases by reflecting the breaking of electric-magnetic duality at the level of perturbations. In particular, the four angular propagation speeds in the large-multipole limit are different from each other for both the electric and magnetic BHs. This suggests the breaking of eikonal correspondence between the peak position of at least one of the potentials of dynamical perturbations and the radius of photon sphere. For the electrically and magnetically charged cases, we elucidate parameter spaces of the HVT coupling and the BH charge in which the BHs without naked singularities are linearly stable.

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A novel test of gravity via black hole eikonal correspondence

Cited by 2 publications

References 0 publications

Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗

Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗

Linear stability of vector Horndeski black holes

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