Article
Astronomy & Astrophysics
M. Bousder, M. Bennai
Summary: This study investigates the charge of the 4D-Einstein-Gauss-Bonnet black hole by examining the charge of a particle-antiparticle pair at r(-) and r(+) horizons, showing the existence of two types of Schwarzschild black holes and quantified values for the Einstein-Gauss-Bonnet black hole charge. The study also reveals the Hawking-Bekenstein formula with two logarithmic corrections, where the second correction depends on the cosmological constant and the black hole charge. Finally, the thermodynamics of the EGB-AdS black hole is explored.
Article
Astronomy & Astrophysics
Uma Papnoi, Farruh Atamurotov
Summary: A charged rotating black hole was constructed in 4D Einstein-Gauss-Bonnet gravity from a charged black hole in 4D EGB gravity using complex coordinate transformations suggested by Newman-Janis. The null geodesics were studied to investigate the shadow shape cast by a rotating charged black hole in 4D EGB gravity, with analysis on the influence of Gauss-Bonnet term and black hole charge on horizon, shadow, effective potential, and energy emission rate. The Gauss-Bonnet parameter was found to have an impact on the shape and size of the shadow, as well as on the effective potential, horizon, and energy emission rate.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Physics, Particles & Fields
Yi-Li Wang, Xian-Hui Ge
Summary: This paper investigates the Einstein-Maxwell-Gauss-Bonnet-axion theory in 4-dimensional spacetime through a Kaluza-Klein-like process. By obtaining the dyonic black hole solution coupled with higher derivative terms, the behavior of shear viscosity to entropy density ratio at different temperatures is studied. It is found that the ratio of uncharged black holes violates a specific bound at low temperatures, and the main feature of this ratio remains almost unchanged in 4 dimensions.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Nisha Godani, Dharm Veer Singh, Gauranga C. Samanta
Summary: In this paper, we construct a thin-shell wormhole in 4D Einstein-Gauss-Bonnet gravity and investigate its stability condition using linear and nonlinear models of the exotic fluid at the throat. We also examine the validity of energy conditions for the wormholes. The results show that the energy conditions are violated in the linear model but satisfied in the nonlinear model. Additionally, we find 4D wormhole solutions in EGB gravity for specific choices of equilibrium radius and equation of state parameter.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Multidisciplinary Sciences
Sergey Il'ich Kruglov
Summary: A new exact spherically symmetric and magnetically charged black hole solution is obtained in the Glavan and Lin regularization scheme, with a focus on thermodynamics properties, phase transitions, and stability within a certain range of event horizon radii. The calculation of the BH shadow radius and its dependence on model parameters are also studied.
Article
Physics, Multidisciplinary
Ambuj Kumar Mishra, Shweta, Umesh Kumar Sharma
Summary: In this paper, wormholes in 4D Einstein-Gauss-Bonnet gravity are investigated without the need for exotic matter. The results show that the negative branch wormhole solutions satisfy the null energy conditions (NEC) throughout the entire space-time, while the positive branch reduces exactly to Morris-Thorne of GR.
PRAMANA-JOURNAL OF PHYSICS
(2022)
Article
Astronomy & Astrophysics
Eugeny Babichev, William T. Emond, Sabir Ramazanov
Summary: We study black holes in a modified gravity scenario involving a scalar field quadratically coupled to the Gauss-Bonnet invariant. The nonminimal coupling to gravity leads to symmetry restoration near the black hole horizon, prompting the development of the scalar wall in its vicinity. The model is fully consistent with the existence of an inflationary stage and predicts the speed of gravitational waves to be extremely close to unity.
Article
Physics, Particles & Fields
Jing Li, Songbai Chen, Jiliang Jing
Summary: The study revealed that tidal forces and geodesic deviation motion strongly depend on the sign of the Gauss-Bonnet coupling constant, with stronger tidal forces for negative constants and weaker forces for positive ones. The behavior of tidal force is similar to that in Schwarzschild spacetime for negative coupling constants, and to that in Reissner-Nordstrom black hole for positive constants as observed in the study.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
M. Bousder, K. El Bourakadi, M. Bennai
Summary: This paper investigates the thermodynamic properties of four-dimensional Einstein-Gauss-Bonnet black holes, obtaining thermodynamic variables and equations of state through a new parameterization, and discussing the effects of temperature on P - V isotherms. The study shows the influence of the Cauchy horizon on thermodynamic parameters, and proves that black hole entropy follows the area law with a logarithmic correction that has physical significance. Additionally, the study extends to extremal EGB black holes and examines the relationship between compressibility factor, specific heat, and the coupling alpha.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
Sandipan Sengupta
Summary: In this study, we establish an Einstein-Gauss-Bonnet theory in four dimensions based on extra dimensions with vanishing metrical length. The effective field equations of the theory depend solely on the four-metric and exhibit a quadratic curvature nonlinearity without higher than second-order derivatives. Unlike previous proposals, our formalism does not require classical regularization of divergences and is not equivalent to Horndeski gravity. The theory is generally covariant and independent of compactification. The vacuum field equations allow for FLRW cosmologies with nonsingular bounce and self-accelerating Universe, as well as spherically symmetric black holes more general than Schwarzschild. Furthermore, the quadratic theory of gravity remains valid against the inclusion of higher Lovelock densities in 5 + 2n dimensions.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Mina Y. Ghodsi, Aryan Behnamfard, Saeed Fakhry, Javad T. Firouzjaee
Summary: A novel 4-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity model has been proposed, which shows a higher ISW effect compared to the Lambda-CDM (Λ CDM) model. The study explores the evolution of the gravitational potential, linear growth factor, ISW-auto power spectrum, and ISW-cross power spectrum in the 4D EGB model, revealing that the amplitude of the ISW power spectrum is amplified, suggesting a relative advantage of the 4D EGB model over the Λ CDM one.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Physics, Nuclear
Kimet Jusufi
Summary: Using a modified expression for the electric potential in the context of T-duality, an exact charged solution is obtained within the 4D Einstein-Gauss-Bonnet (4D EGB) theory of gravity in the presence of a cosmological constant. The solution is also shown to exist in the regularized 4D EGB theory, and a correspondence between the black hole solution in the 4D EGB theory and the solution in the non-relativistic Horava-Lifshitz theory is pointed out. The black hole solution is regular and singularity-free, and a class of well known solutions in the literature is derived as a special case.
Article
Physics, Multidisciplinary
Dharm Veer Singh, Benoy Kumar Singh, Sudhaker Upadhyay
Summary: The study derives an exact black hole solution for Einstein-Gauss-Bonnet gravity with Yang-Mills field in 4D AdS spacetime, and investigates its thermodynamic properties to calculate black hole mass, temperature, entropy, and heat capacity. The presence of Yang-Mills field modifies the thermodynamic quantities, but the entropy remains unaffected by the Yang-Mills charge. The solution exhibits P-v criticality and belongs to the universality class of Van der Waals fluid.
Article
Physics, Multidisciplinary
Doris Samart, Phongpichit Channuie
Summary: This paper investigates the thermal phase transition from asymptotic anti-de Sitter to de Sitter geometries in the context of four-dimensional Einstein-Gauss-Bonnet gravity, showing that the transitions occur within a narrow coupling range.
ANNALEN DER PHYSIK
(2022)
Article
Astronomy & Astrophysics
M. Zubair, Muhammad Ali Raza
Summary: This paper derives a rotating black hole metric by using the modified Newman-Janis algorithm in the Einstein-Gauss-Bonnet massive gravity. The influence of graviton mass (m) and the Gauss-Bonnet parameter (α) on the horizon and photon sphere radii of rotating and non-rotating black holes is studied. The effects of graviton mass on the effective potential, shadow, distortion, and energy emission rate are investigated using the Hamilton-Jacobi method and Bardeen's procedure of impact parameters. The findings reveal that graviton mass has a significant impact on the shadow and related physical observables. The collision of two uncharged particles near the black hole is also analyzed, and the energy of the particles in the center of mass frame is computed for both static and rotating black hole cases. The shadow diameter is compared with Sgr. A* to obtain constraints on the black hole parameters. ©2023 Elsevier B.V. All rights reserved.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Multidisciplinary
Marco A. A. de Paula, Luiz C. S. Leite, Luis C. B. Crispino
Summary: This study investigates the scattering properties of a massless scalar field in the background of a charged Ayon-Beato-Garcia regular black hole solution. Using a numerical approach, the authors compute the differential scattering cross section for arbitrary values of the scattering angle and the incident wave frequency. Comparisons with classical geodesic scattering and semiclassical glory approximation show excellent agreement in corresponding limits. The study also reveals similar scattering properties between Ayon-Beato-Garcia and Reissner-Nordstrom black hole solutions for low-to-moderate values of the black hole electric charge and any scattering angle.
EUROPEAN PHYSICAL JOURNAL PLUS
(2022)
Article
Astronomy & Astrophysics
Marco Aurelio Abreu de Paula, Luiz Carlos dos Santos Leite, Luis Carlos Bassalo Crispino
Summary: The scattering cross section of massless scalar waves in the background of an Ayon-Beato-Garcia electrically charged regular black hole is investigated. The scattering pattern is obtained by solving the Klein-Gordon equation numerically. It is shown that the Ayon-Beato-Garcia regular black hole can mimic the scattering properties of the Reissner-Nordstrom black hole for arbitrary values of the scattering angle and wave frequency, considering low-to-moderate values of the normalized electric charge. Our results suggest that the scattering spectra of regular and standard black holes can be indistinguishable.
ASTRONOMISCHE NACHRICHTEN
(2023)
Editorial Material
Astronomy & Astrophysics
Marco Aurelio Abreu de Paula, Luiz Carlos dos Santos Leite, Luis Carlos Bassalo Crispino
GENERAL RELATIVITY AND GRAVITATION
(2023)
Article
Astronomy & Astrophysics
Zeus S. Moreira, Haroldo C. D. Lima Jr, Luis C. B. Crispino, Carlos A. R. Herdeiro
Summary: In this study, we analyze the quasinormal modes (QNMs) of a Schwarzschild black hole with corrections motivated by Loop Quantum Gravity (LQG). The black hole exhibits a global structure of a black bounce, and the QNM frequency orbits in the complex plane are self-intersecting spiraling curves. The overall damping decreases with increasing LQG parameter, and the spectrum of the quantum corrected black hole shows an oscillatory pattern with possible QNMs having vanishing real part.
Article
Astronomy & Astrophysics
Sergio V. M. C. B. Xavier, Haroldo C. D. Lima Junior, Luis C. B. Crispino
Summary: We investigate the shadow and gravitational lensing effects of a supermassive black hole immersed in a dark matter halo, comparing it with an isolated Schwarzschild black hole. Multiple light rings emerge when the dark matter distribution concentrates near the black hole's event horizon, resulting in significantly different shadows and gravitational lensing compared to the Schwarzschild black hole. We constrained the parameters of the dark matter halo using shadow data obtained from the Event Horizon Telescope collaboration for M87* and SgrA*.
Article
Astronomy & Astrophysics
Sergio V. M. C. B. Xavier, Carolina L. Benone, Luiz C. S. Leite, Luis C. B. Crispino
Summary: In this study, we investigate the scattering behavior of axially incident massless scalar waves by the Kerr-Sen black hole, a charged and rotating black hole solution from heterotic string theory. We calculate the scattering cross section using the partial wave approach for arbitrary incident wavelengths, and compare our results with those of the Kerr-Newman black hole, the general relativistic version of a charged and rotating black hole. Our numerical results demonstrate that these compact objects exhibit similar scattering properties.
Article
Astronomy & Astrophysics
Joao P. B. Brito, Rafael P. Bernar, Luis C. B. Crispino
Summary: Investigated the scalar radiation emitted by a source orbiting a Schwarzschild-anti-de Sitter black hole in curved spacetime; discussed the variation of emitted power for different sizes of black holes.
Article
Physics, Particles & Fields
Renan B. Magalhaes, Luiz C. S. Leite, Luis C. B. Crispino
Summary: In this study, we investigate the scattering of light-like geodesics and massless scalar waves by a static Konoplya-Zhidenko black hole, considering a single deformation parameter in the parametrized black hole solution. By analyzing the geodesics, we compute the classical differential scattering cross section and examine the influence of the deformation parameter on null trajectories. We also study the propagation of a massless scalar field near the black hole and calculate the differential scattering cross section using the plane waves formalism. Our numerical results are in excellent agreement with the glory approximation when considering the backward direction. Comparing the results for the deformed black hole with the Schwarzschild case, we find that the additional parameter plays an important role in the behavior of the scattering process for moderate-to-high scattering angles.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
Haroldo C. D. Lima Junior, Carolina L. Benone, Luis C. B. Crispino
Summary: The scattering of monochromatic planar scalar waves in different spacetime geometries is studied and numerically calculated. It is found that the scattering results for regular black holes are similar to traditional black holes, while the results for wormholes are significantly different. In particular, the differential scattering cross section for wormholes decreases considerably at large scattering angles for resonant frequencies.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
Haroldo C. D. Lima, Mateus M. Correa, Caio F. B. Macedo, Luis C. B. Crispino
Summary: This study investigates the tidal forces phenomenon of black holes in the presence of effective matter fields. It reveals characteristic differences in tidal forces between "dirty" black holes and vacuum black holes. The research is significant for understanding the interaction of black holes with their surrounding environments.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Haroldo C. D. Lima Junior, Jian-Zhi Yang, Luis C. B. Crispino, Pedro V. P. Cunha, Carlos A. R. Herdeiro
Summary: The study investigates the characteristics of the generalized Schwarzschild-Melvin solution in Einstein-Maxwell-dilaton theory. It finds that the change in dilaton coupling a leads to a discontinuous transition of the topological charge (TC) from 0 to -1, which is related to the asymptotics and shadow effects of the Schwarzschild-Melvin solution.
Article
Astronomy & Astrophysics
Renan B. Magalhaes, Luis C. B. Crispino, Gonzalo J. Olmo
Summary: We study the correspondence between the solutions of general relativity (GR) and Ricci-based gravity theories (RBGs) of the f(R, Q) type. By focusing on the case of scalar matter, we establish the correspondence between the two theories for arbitrary f(R, Q) Lagrangian, with simplifications that arise when considering a free massless scalar in the GR frame. Using a spherically symmetric, static solution as a seed, we generate new compact objects in the target theory and find two types of solutions: one representing naked singularities and another corresponding to asymmetric wormholes with bounded curvature scalars everywhere, although the latter solutions are geodesically incomplete.
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Octavio C. Junqueira
Summary: This study investigates the influence of rotation on the transition temperature of strongly interacting matter produced in non-central heavy ion collisions. By using a holographic description of an AdS black hole, the authors extend the analysis to the more realistic case where the matter spreads over a region around the rotational axis. The results show the coexistence of confined and deconfined phases and are consistent with the concept of local temperature in rotating frames developed by Tolman and Ehrenfest.
Article
Astronomy & Astrophysics
Bing Sun, Jiachen An, Zhoujian Cao
Summary: This paper investigates the effect of gravitational constant variation on the propagation of gravitational waves. By employing two analytical methods, the study finds that variations in the gravitational constant result in amplitude and phase corrections for gravitational waves, and the time variation of the gravitational constant can be constrained through the propagation of gravitational waves.
Article
Astronomy & Astrophysics
Abdellah Touati, Zaim Slimane
Summary: This letter presents the first study of Hawking radiation as a tunneling process within the framework of non-commutative gauge theory of gravity. The non-commutative Schwarzschild black hole is reconstructed using the Seiberg-Witten map and the star product. The emission spectrum of outgoing massless particles is computed using the quantum tunneling mechanism. The results reveal pure thermal radiation in the low-frequency scenario, but a deviation from pure thermal radiation in the high-frequency scenario due to energy conservation. It is also found that noncommutativity enhances the correlations between successively emitted particles.
Article
Astronomy & Astrophysics
Shahar Hod
Summary: The travel times of light signals between two antipodal points on a compact star's surface are calculated for two different trajectories. It is shown that, for highly dense stars, the longer trajectory along the surface may have a shorter travel time as measured by asymptotic observers. A critical value of the dimensionless density-area parameter is determined for constant density stars to distinguish cases where crossing through the star's center or following a semi-circular trajectory on the surface has a shorter travel time as measured by asymptotic observers.
