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Extended gravitational models have gained large attention in the last couple of decades. In this work, we examine the solution space of vacuum, static, and spherically symmetric spacetimes within $F(R)$ theories, introducing novel methods…

General Relativity and Quantum Cosmology · Physics 2024-11-11 Cristobal Laporte , Agustín Silva

In this manuscript, we show that the external Schwarzschild metric can be a good approximation of exact black hole solutions of entangled relativity. Since entangled relativity cannot be defined from vacuum, the demonstrations need to rely…

General Relativity and Quantum Cosmology · Physics 2021-08-04 Olivier Minazzoli , Edison Santos

We find an exact black hole solution with a minimally coupled scalar field. The corresponding spacetime has two horizons and one of the them is the black hole event horizon and the other is the cosmic horizon. In this sense, the solution is…

General Relativity and Quantum Cosmology · Physics 2020-10-13 Shuang Yu , Changjun Gao

We study geometrically thick non-self gravitating equilibrium tori orbiting a Schwarzschild black hole immersed in swirling universes. This solution is axially symmetric and non-asymptotically flat, and its north and south hemispheres spin…

General Relativity and Quantum Cosmology · Physics 2024-02-06 Chengjia Chen , Qiyuan Pan , Jiliang Jing

According to the no-hair theorem, static black holes are described by a Schwarzschild spacetime provided there are no other sources of the gravitational field. This requirement, however, is in astrophysical realistic scenarios often…

General Relativity and Quantum Cosmology · Physics 2015-06-24 Norman Gürlebeck

We examine the behavior of non-commutative Schwarzschild black holes in the context of massive gravity. According to the investigation, corresponding to a minimal mass, the black hole can have two horizons, one horizon, or no horizon at…

General Relativity and Quantum Cosmology · Physics 2024-04-17 Piyali Bhar , Dhruba Jyoti Gogoi , Supakchai Ponglertsakul

In this work the model is constructed to describe the black hole enclosed in the dust cosmological background in case of zero spatial curvature. This model is based on our exact solution of the class of LTB inhomogeneous solutions. We…

General Relativity and Quantum Cosmology · Physics 2017-11-29 Pavlina Jaluvkova , Elena Kopteva , Zdenek Stuchlik

The motion of superluminal particles in the gravitational field of a non-rotating black hole is analyzed. The relativistic Hamilton-Jacobi equation is solved for particles with imaginary rest mass. It is shown that there are no stable…

General Relativity and Quantum Cosmology · Physics 2013-01-24 V. M. Lipunov

This paper examines the general relativistic model of a geometrically thick configuration of an accretion disc around an electrically charged black hole in an accelerated motion, as described by the C-metric family. We aim to study the…

High Energy Astrophysical Phenomena · Physics 2025-02-14 Shokoufe Faraji , Audrey Trova , Vladimir Karas

The nature of the super-massive black hole candidates in galactic nuclei can be tested by analyzing the profile of the K$\alpha$ iron line observed in their X-ray spectrum. In this paper, we consider the possibility that the spacetime in…

General Relativity and Quantum Cosmology · Physics 2013-09-12 Cosimo Bambi , Daniele Malafarina

In the present work, accretion onto a static spherically symmetric black hole in the hybrid metric-Palatini gravity is considered. The Novikov-Thorne model for a relativistic thin accretion disk is used. The energy flux, temperature…

General Relativity and Quantum Cosmology · Physics 2024-02-05 P. I. Dyadina , N. A. Avdeev

This article outlines the search for an exact general relativistic description of the exterior (vacuum) gravitational field of a rotating spheroidal black hole surrounded by a realistic axially symmetric disc of matter. The problem of…

General Relativity and Quantum Cosmology · Physics 2016-11-09 O. Semerak

Within the Relativistic Theory of Gravitation it is shown that the equation of state $p=\rho$ holds near the center of a black hole. For the stiff equation of state $p=\rho-\rho_c$ the interior metric is solved exactly. It is matched with…

General Relativity and Quantum Cosmology · Physics 2008-05-28 Theo M. Nieuwenhuizen

We study static black holes in quadratic gravity with planar and hyperbolic symmetry and non-extremal horizons. We obtain a solution in terms of an infinite power-series expansion around the horizon, which is characterized by two…

General Relativity and Quantum Cosmology · Physics 2023-02-28 Alena Pravdova , Vojtech Pravda , Marcello Ortaggio

Black hole physics currently lacks a fully coherent understanding of the black hole mass (density), entropy, and interior (non-)singularity. These concepts are related to the black hole radius, area (of the horizon), and volume (within the…

General Relativity and Quantum Cosmology · Physics 2026-05-20 Arno Keppens , Lester Kurvers

One of the most remarkable predictions of the general theory of relativity is the existence of black-hole "photonspheres", compact null hypersurfaces on which massless particles can orbit the central black hole. We prove that every…

General Relativity and Quantum Cosmology · Physics 2017-02-01 Shahar Hod

Recently, the image of a Schwarzschild black hole with an accretion disk has been revisited, and it showed that the "photon ring", defined as highly bent light rays that intersect the disk plane more than twice, is extremely narrow and…

General Relativity and Quantum Cosmology · Physics 2021-08-25 Qingyu Gan , Peng Wang , Houwen Wu , Haitang Yang

We investigate a static, spherically symmetric black hole solution arising from Einstein gravity coupled to a confining nonlinear electrodynamics model that reproduces Maxwell theory in the strong-field regime while introducing…

High Energy Astrophysical Phenomena · Physics 2025-12-23 Erdem Sucu , Izzet Sakallı , Orhan Donmez , G. Mustafa

We study static spherically symmetric solutions to the vacuum field equations of quadratic gravity in the presence of a cosmological constant $\Lambda$. Motivated by the trace no-hair theorem, we assume the Ricci scalar to be constant…

General Relativity and Quantum Cosmology · Physics 2021-03-26 Vojtech Pravda , Alena Pravdova , Jiri Podolsky , Robert Svarc

The phenomenology of a radiating Schwarzschild black hole is analyzed in a noncommutative spacetime. It is shown that noncommutativity does not depend on the intensity of the curvature. Thus we legitimately introduce noncommutativity in the…

High Energy Physics - Theory · Physics 2011-02-22 Piero Nicolini