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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…

Pulsars orbiting around the black hole at our galactic center provide us a unique testing site for gravity. In this work, we propose an approach to probe the gravity around the black hole introducing two phenomenological parameters which…

General Relativity and Quantum Cosmology · Physics 2016-07-20 Kengo Iwata , Chul-Moon Yoo

We consider static black holes in Einstein gravity and study parameters characterizing the black hole size, namely the radii of the horizon $R_+$, photon sphere $R_{\rm ph}$ and black hole shadow $R_{\rm sh}$. We find a sequence of…

General Relativity and Quantum Cosmology · Physics 2020-03-04 H. Lu , Hong-Da Lyu

Our study investigates the astronomical implications of Rastall gravity, particularly its behavior amidst a radiation field compared to Reissner-Nordstrom (RN) black holes. Our research delineates a crucial correlation between the dynamics…

General Relativity and Quantum Cosmology · Physics 2024-06-19 Yu-Xiang Huang , Sen Guo , Yu Liang , Yu-Hao Cui , Qing-Quan Jiang , Kai Lin

We reconstruct a static and spherically symmetric black hole geometry originally proposed as an effective metric by identifying a consistent matter source derived from a fundamental action. The space-time is supported by a magnetically…

The Kerr black holes possess a photon region with prograde and retrograde orbits radii, respectively, $M\leq r_p^-\leq 3M$ and $3M\leq r_p^+\leq 4M$, and thereby always cast a closed photon ring or a shadow silhouette for $a\leq M$. For…

General Relativity and Quantum Cosmology · Physics 2021-03-25 Rahul Kumar , Sushant G. Ghosh

In a scalar-vector-gravity theory with the vector sector described by nonlinear electrodynamics, the field equations are integrated using the well-known gravitational decoupling method. The resulting spacetime corresponds to a spherically…

General Relativity and Quantum Cosmology · Physics 2026-03-31 Manuel Gonzalez-Espinoza , Y. Gómez-Leyton , Z. Stuchlik , Francisco Tello-Ortiz

This study investigates the effects of higher dimensions on the observable properties of Schwarzschild-Tangherlini black holes, focusing on the photonsphere, shadow radius, deflection angles, and quasinormal modes (QNMs). By extending…

General Relativity and Quantum Cosmology · Physics 2025-06-27 Nikko John Leo S. Lobos , Anele M. Ncube , Reggie C. Pantig , Alan S. Cornell

In this work, we examine the influence of nonlinear electrodynamics (NED) and $f(R,T)$ gravity on quasi-periodic oscillations (QPOs) around a magnetically charged black hole. By analyzing the effective potential, specific energy, and…

General Relativity and Quantum Cosmology · Physics 2025-08-05 Bidyut Hazarika , Abhishek Baruah , Prabwal Phukon

In the present paper we consider the extended scalar-tensor-Gauss-Bonnet gravity with a massive scalar field. We prove numerically the existence of Gauss-Bonnet black holes for three different forms of the coupling function including the…

General Relativity and Quantum Cosmology · Physics 2019-05-29 Daniela D. Doneva , Kalin V. Staykov , Stoytcho S. Yazadjiev

This work presents a comprehensive investigation of the gravitational phenomena that correspond to a non-commutative (NC) charged black hole, by incorporating NC geometry through a Moyal twist. We derive the deformed metric up to the second…

General Relativity and Quantum Cosmology · Physics 2026-02-26 N. Heidari

In this paper, we investigate the phenomenology of electrically charged black holes in a Lorentz-violating gravitational framework mediated by a background Kalb-Ramond (KR) antisymmetric tensor field. Employing the Gauss-Bonnet theorem in a…

General Relativity and Quantum Cosmology · Physics 2025-08-04 Reggie C. Pantig , Ali Övgün , Ángel Rincón

Nonlinear electrodynamics is known as the generalizations of Maxwell electrodynamics at strong fields and presents interesting features such as curing the classical divergences present in the linear theory when coupled to general…

General Relativity and Quantum Cosmology · Physics 2022-10-04 Yashmitha Kumaran , Ali Övgün

Black hole (BH) shadow observations and gravitational wave astronomy have become crucial approaches for exploring BH physics and testing gravitational theories in extreme environments. This paper investigates the charged black hole with…

General Relativity and Quantum Cosmology · Physics 2025-09-16 Lai Zhao , Meirong Tang , Zhaoyi Xu

In the framework of Einstein-Maxwell-scalar theory, we studied scalar field perturbations of Reissner-Nordstr\"{o}m-Melvin (RNM) black holes, which describes the RN black holes immersed in a uniform magnetic field. Due to the coupling to…

General Relativity and Quantum Cosmology · Physics 2023-02-13 Hengyu Xu , Shao-Jun Zhang

With the help of the Bohr--Sommerfeld quantization rule, the area spectrum of a charged, spherically symmetric spacetime is obtained by studying an adiabatic invariant action variable. The period of the Einstein-Maxwell system, which is…

General Relativity and Quantum Cosmology · Physics 2012-04-23 Xiao-Xiong Zeng , Wen-Biao Liu

We examine the motion of the massless scalar field and nearly bound null geodesics in the near-ring region of a black hole, which may possess either acceleration or a gravitomagnetic mass. Around such black holes, the photon ring deviates…

High Energy Physics - Theory · Physics 2024-03-27 Ye-Sheng Xue , Jie Jiang , Ming Zhang

A charged, non-rotating, spherically symmetric black hole which has cosmological constant $\Lambda$ (Reissner-Nordstr\"om+$\Lambda$ or RN+$\Lambda$), active gravitational mass $M$ and electric charge $Q$ is studied with exterior…

General Physics · Physics 2021-11-17 Safiqul Islam , Priti Mishra , Somi Aktar , Farook Rahaman

In this work, we obtain an expression for the total observational frequency shift of photons emitted by massive geodesic particles circularly orbiting a black hole in a general spherically symmetric background. Our general relations are…

General Relativity and Quantum Cosmology · Physics 2024-03-26 Diego A. Martinez-Valera , Mehrab Momennia , Alfredo Herrera-Aguilar

In this paper, under the illumination of thin disk accretion, we have employed the ray-tracing method to carefully investigate shadows and rings of the Kehagias-Sfetsos(KS) black hole in deformed Ho\v{r}ava-Lifshitz(HL) gravity. The results…

General Relativity and Quantum Cosmology · Physics 2021-06-30 Guo-Ping Li , Ke-Jian He