Article
Astronomy & Astrophysics
Andre Addazi, Salvatore Capozziello, Sergei Odintsov
Summary: In this study, the emergence of black hole shadow and photon-sphere in the context of f(R) gravity is discussed, with a focus on the sensitivity of the shadow to linear instabilities of metric from f(R) solutions. It is found that the photon circular trajectories defining the black hole photon-sphere exhibit double exponential instabilities, leading to two Lyapunov exponents related to chaos in geodesic orbits. This result challenges the black hole chaos bound proposed by Maldacena, Shenker and Stanford for General Relativity, and suggests a new paradigm for handling black hole shadow and gravitational waves observations in the ringdown phase of black hole merging in Extended Theories of Gravity.
Article
Physics, Particles & Fields
Julio C. Fabris, Ednaldo L. B. Junior, Manuel E. Rodrigues
Summary: This article investigates the implementation of black bounce solutions in f(R) theories. It is found that violation of the energy conditions still occurs in these solutions, albeit less severe than in General Relativity (GR) cases. The authors propose a zero-density model with horizons and present a model with positive energy density, which differs from GR.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Wen-Yuan Ai
Summary: A special two-dimensional dilaton gravity theory with an exact solution for the metric has been studied, presenting a gravitational domain wall concept with the event horizon serving as the wall separating two asymptotically Minkowskian spacetimes. The global causal structure and thermodynamical quantities of this object have been investigated, with non-negative entropy and energy observed only when a parameter falls within a specific range.
Article
Physics, Particles & Fields
Adel Awad, Alexey Golovnev, Maria-Jose Guzman, Waleed El Hanafy
Summary: In this paper, we study various forms of diagonal tetrad solutions in f(T) gravity with specific symmetries. We find that constant torsion scalar is required for all possible horizon topologies, regardless of spherical, hyperbolic, or planar. We provide a full classification of vacuum static solutions and discuss the addition of time-dependence. Furthermore, we discover that the presence of matter is necessary for non-trivial solutions in the case of planar symmetry.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Che-Yu Chen, Sohyun Park
Summary: The study reveals that in the nonlocal gravity model, axial gravitational perturbations are identical to those in general relativity, while polar modes differ when scalar fields are excited, breaking the isospectrality between axial and polar modes. The same conclusion is reached when analyzing the predecessor of this model.
Article
Astronomy & Astrophysics
Ping Li, Yong-Qiang Liu, Xiang-Hua Zhai
Summary: This paper presents a detailed study of nonrotating and rotating black hole solutions in the f (R) = R - 2 alpha root R model, and proposes two strategies to simplify the search for analytic solutions.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2022)
Article
Astronomy & Astrophysics
G. G. L. Nashed, A. Sheykhi
Summary: We present two new classes of analytical solutions in the framework of f (R) gravity. These solutions describe non-rotating and rotating black holes, respectively, and have non-trivial values of the Ricci scalar. The obtained solutions exhibit strong singularities in spacetime, indicating a change in the causal structure caused by the higher-order derivative terms in f (R) gravity.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Astronomy & Astrophysics
Frank Saueressig, Mina Galis, Jesse Daas, Amir Khosravi
Summary: Black holes are fascinating objects in the universe, determined solely by their mass according to general relativity, with curvature singularities within their event horizon. Using the Frobenius method to study black hole solutions in quadratic gravity, it is argued that only the Schwarzschild solution is visible in this approach.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2021)
Article
Physics, Particles & Fields
Oscar J. C. Dias, Gary T. Horowitz, Jorge E. Santos
Summary: We studied the interior of a family of asymptotically flat, charged black holes that develop scalar hair as charge increases. These black holes resemble the interior of a holographic superconductor and exhibit analogs of Josephson oscillations of the scalar field. The presence of Cauchy horizons in a large class of stationary black holes with scalar hair was argued against in an appendix.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Phuwadon Chunaksorn, Ekapong Hirunsirisawat, Ratchaphat Nakarachinda, Lunchakorn Tannukij, Pitayuth Wongjun
Summary: The thermodynamic properties of the de Rham-Gabadadze-Tolley black hole in the asymptotically de Sitter spacetime were investigated using Renyi entropy. It was found that the black hole described by standard Gibbs-Boltzmann statistics in the asymptotically de Sitter spacetime cannot be thermodynamically stable. The system generally had two horizons corresponding to two thermodynamic systems with different temperatures, resulting in a non-equilibrium state. By using alternative Renyi statistics, it was possible to obtain a stable de Rham-Gabadadze-Tolley black hole. The study also identified differences between the separated system approach and the effective system approach, such as temperature profiles and types of the Hawking-Page phase transition.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
G. G. L. Nashed, Shin'ichi Nojiri
Summary: The study explores a novel black hole solution in the f(R) gravitational theory for rotating black hole spacetime, showing it has strong singularity but stability. The analysis of thermodynamic quantities and Cauchy horizons distinguishes it from black holes in general relativity. Additionally, the black hole's positive Gibbs free energy indicates stability, with stability conditions derived analytically and graphically.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Physics, Particles & Fields
Gaston Giribet, Edmundo Lavia
Summary: This study successfully determined the correct mass of the Lifshitz black hole in higher-derivative massive gravity using a robust method, with results consistent with computations inspired by holography despite an odd normalization of the gravity action for the mass spectrum to be positive.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Sudhaker Upadhyay, Saheb Soroushfar, Reza Saffari
Summary: This paper investigates the thermodynamic properties and corrections of a static black hole in f(R) gravity theory, finding that correction parameters affect the thermodynamic behavior. The study also shows the relationship between curvature scalar singularities and phase transition points of the black hole, with deviations occurring as the correction parameter increases.
MODERN PHYSICS LETTERS A
(2021)
Article
Astronomy & Astrophysics
Moises Bravo-Gaete, Maria Montserrat Juarez-Aubry, Gerardo Velazquez Rodriguez
Summary: In this work, we study the existence of asymptotically Lifshitz black holes in four dimensions with a negative cosmological constant. We consider two scenarios, including dilatonic fields and a nonminimally coupled scalar field. We find solutions for specific values of the dynamical exponent, as well as additional solutions in the limiting case. We also study the thermodynamics of these new solutions and find that they satisfy the first law of thermodynamics and the Smarr relation.
Article
Physics, Mathematical
F. Darabi, M. Golmohammadi, A. Rezaei-Aghdam
Summary: In this paper, we employ the Hojman symmetry approach to investigate new solutions in (2+1)-dimensional f(R) gravity theory, in comparison with the Noether symmetry approach. In the special case where the Hojman symmetry vector X = R, we obtain solutions that coincide with the (2+1)-dimensional Banados-Teitelboim-Zanelli (BTZ) black hole and generalized (2+1)-dimensional BTZ black hole solutions obtained using the Noether symmetry approach. Notably, the cosmological constant is directly linked to the manifestation of Hojman symmetry.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2022)
Article
Astronomy & Astrophysics
Behzad Eslam Panah, Khadijie Jafarzade
Summary: This paper investigates the thermodynamic features of charged rotating accelerating black holes in anti-de Sitter spacetime. It analyzes thermal stability/instability using heat capacity in the canonical ensemble, and studies the effects of angular momentum, electric charge, and string tension on thermodynamic quantities and system stability. By considering the known relation between pressure and the cosmological constant, critical quantities are extracted and the impacts of the mentioned parameters on them are discussed. Furthermore, a heat engine is constructed using the black hole as the working substance, and the heat engine efficiency is obtained by considering a rectangular heat cycle in the P-V plane. The effects of black hole parameters on the efficiency are examined and their effective roles are analyzed. Finally, the paper investigates the conditions for a consistent fulfillment of the thermodynamic second law by comparing the engine efficiency with Carnot efficiency.
GENERAL RELATIVITY AND GRAVITATION
(2022)
Article
Physics, Particles & Fields
S. N. Sajadi, S. H. Hendi
Summary: In this study, an analytical approximate rotating black hole solution for quadratic gravity (QG) is obtained by constructing near-horizon and asymptotic solutions and using a continued fraction method. The thermodynamics of the black hole solution is investigated by checking the first law of thermodynamics and the Smarr formula. Various physical properties of the solution, including its photon sphere and shadow, are also investigated.
Article
Physics, Multidisciplinary
B. Eslam Panah
Summary: In this paper, general uncharged accelerating BTZ black hole solutions are extracted and some of their properties are studied. The analysis reveals that the spacetime's asymptotic behavior depends on four parameters: the cosmological constant, mass, acceleration, and topological constant. The temperature of these black holes is found to be always positive for AdS spacetime. Charged accelerating BTZ black hole solutions in the presence of a conformally invariant Maxwell field are also investigated. The findings show a coupling between the electrical charge and other quantities of the accelerating BTZ black holes. The asymptotic behavior and temperature of charged accelerating BTZ black holes are studied, with the temperature depending on the electrical charge, accelerating parameter, and cosmological constant.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
S. H. Hendi, S. Hajkhalili, S. Mahmoudi
Summary: A new model of regular black hole in 2+1 dimensions is proposed by considering an appropriate matter field as the energy-momentum tensor. The model introduces an upper bound on the radius of the event horizon and a lower bound on the mass, motivated by astrophysical black holes. The solutions obtained are investigated for their geometric properties and found to be thermally stable in the mentioned admissible domain.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2023)
Article
Astronomy & Astrophysics
S. H. Hendi, Kh Jafarzade, B. Eslam Panah
Summary: The recent observations of M87* by the EHT have sparked interest in studying the shadow of black holes, as well as investigating the time evolution and lifetime of black holes to refine theoretical models in gravitating systems. In this study, we focus on the optical features of a charged AdS black hole in dRGT massive gravity, such as its shadow geometrical shape and energy emission rate, to narrow down the free parameters of the theory. Our main goal is to compare the rotating counterpart of the static black hole solution in dRGT massive gravity with EHT data to determine the allowed regions of the model parameters. Additionally, we analyze how the rotation factor and other parameters impact the emission of particles around the black holes.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Multidisciplinary
Kh Jafarzade, E. Rezaei, S. H. Hendi
Summary: This article investigates the geometric properties, optical features, and thermodynamic behavior of a class of rotating Lifshitz-like black hole solutions in Horava-Lifshitz gravity. Examinations on the impact of electric charge, angular momentum, and exponents on the optical characteristics and thermodynamics are conducted, including the existence of a van der Waals-like phase transition. A holographic heat engine is also constructed to study the efficiency of the black hole. The second law of thermodynamics is examined by comparing the efficiency of the black hole heat engine with the Carnot heat engine efficiency.
PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS
(2023)
Article
Astronomy & Astrophysics
B. Eslam Panah
Summary: By considering a three-dimensional C-metric and introducing energy dependence, we construct a three-dimensional energy-dependent C-metric. We then obtain accelerating BTZ black hole solutions in gravity's rainbow. Moreover, we find that (A)dS black holes have an event horizon depending on all the parameters of this theory. The temperature and entropy of these black holes are calculated and analyzed, with the heat capacity indicating different behaviors based on the cosmological energy-dependent constant. Finally, we show that accelerating AdS BTZ black holes can satisfy both physical conditions and local stability.
Article
Astronomy & Astrophysics
S. H. Hendi, A. Nemati
Summary: In this paper, the Einstein-massive gravity coupled to the Yang-Mills gauge field in five dimensions is studied. The thermodynamic behavior of the static solutions with planar horizon geometry in the extended phase space is explored, and the validity of the first law of thermodynamics is examined using the Hessian matrix. A van der Waals like phase transition is observed for this kind of solution, despite the planar topology of the boundary. The critical quantities and the effects of the massive and Yang-Mills parameters on them are determined. Additionally, the details of the first order phase transition such as the swallow-tail behavior of the Gibbs free energy and divergencies of the specific heat are discussed.
Article
Physics, Multidisciplinary
B. Eslam Panah, M. Khorasani, J. Sedaghat
Summary: In this article, we investigated the three-dimensional C-metric in the F(R) theory of gravity with and without a matter field, and obtained exact solutions for accelerating black holes. The effects of various parameters on the metric function, roots, and temperature of the black holes were studied. We also considered the coupling of nonlinear electrodynamics as a matter field to obtain charged black hole solutions and evaluated the effects of different parameters on the solutions, roots, and temperature. The results showed a dependency on various parameters, and the temperature of the black holes was positive after a certain root.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Physics, Particles & Fields
B. Eslam Panah, M. E. Rodrigues
Summary: In this paper, exact phantom (A)dS black hole solutions are obtained in the context of F(R) gravity with topological spacetime in four dimensions. The effects of different parameters on the event horizon are studied. The conserved and thermodynamic quantities of the system are calculated, and the first law of thermodynamics for these types of black holes is checked. The local stability of the topological phantom (A)dS black holes in F(R) gravity is evaluated by studying the heat capacity and the geometrothermodynamics, which show agreement. The global stability is investigated using the Gibbs potential and the Helmholtz free energy, and the effects of different parameters on local and global stabilities are highlighted.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
H. Barzegar, M. Bigdeli, G. H. Bordbar, B. Eslam Panah
Summary: In this work, we investigate the properties of three-dimensional AdS gravitational vacuum stars (gravastars) in the framework of gravity's rainbow theory, with the inclusion of the Maxwell electromagnetic field. Our analysis includes the computation of physical parameters and the exploration of stability for charged and uncharged gravastars. The results demonstrate that the physical characteristics of the gravastars are influenced by the rainbow functions and electric field.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
S. N. Sajadi, Ali Hajilou, S. H. Hendi
Summary: In this paper, analytical approximate black hole solutions are derived in the framework of f (R) gravity without a cosmological constant. The equations of motion are applied to a spherically symmetric spacetime with one unknown function, resulting in black hole solutions that are not constrained by the Ricci scalar. Near horizon and asymptotic solutions are obtained and combined using a continued-fraction expansion to yield a complete solution. The stability of the solutions is then investigated through the use of thermodynamics and quasi-normal modes.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
A. Bagheri Tudeshki, G. H. Bordbar, B. Eslam Panah
Summary: Investigating the presence of massive gravitons in the field of massive gravity is crucial for understanding the structure of compact objects. In this study, we used numerical methods to calculate the properties of dark energy stars and found that their maximum mass and radius depend on the free parameters and anisotropy parameter of massive gravity.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Astronomy & Astrophysics
H. Barzegar, B. Eslam Panah, G. H. Bordbar, M. Bigdeli
Summary: This paper investigates a new model of (2 + 1)-dimensional gravitational vacuum stars with an isotropic matter distribution anti-de Sitter spacetime in the context of massive gravity. By exploring free singularity models with a specific equation of state and using Mazur-Mottola's approach, the paper predicts 3D gravastars as alternatives to BTZ black holes in massive gravity. Analytical solutions to the interior of gravastars that are free of singularities and event horizons are found. The length, energy, and entropy of a thin shell containing an ultra-relativistic stiff fluid are discussed. The parameter of massive gravity plays a significant role in predicting the proper length, energy contents, entropy, and parameters of gravastars.
