Article
Astronomy & Astrophysics
J. Ovalle, E. Contreras, Z. Stuchlik
Summary: The research indicates that the cosmological constant is deformed near a black hole, leading to a reexamination of the black hole solution and the proposal of a new, simpler and more geometrically rich solution. A detailed study of the new black hole solution was carried out, showing the impact of rotation on the curvature, and a conjecture was made regarding its possible implications on alternative theories.
Article
Mathematics, Applied
Peter Hintz
Summary: The article presents a method for constructing dynamical many-black-hole spacetimes with well-controlled asymptotic behavior as solutions of the Einstein vacuum equation. It involves gluing different types of black hole metrics around points on the future conformal boundary of de Sitter space and solving the Einstein equation while considering scattering data. The main step in the construction is solving a linear divergence equation for trace-free symmetric 2-tensors, which is closely related to Friedrich's analysis of scattering problems on asymptotically simple spacetimes.
COMMUNICATIONS IN PARTIAL DIFFERENTIAL EQUATIONS
(2021)
Article
Physics, Particles & Fields
Eunice Omwoyo, Humberto Belich, Julio C. Fabris, Hermano Velten
Summary: This work focuses on analyzing the shadows generated by Kerr-de Sitter and Kerr-de Sitter Revisited black holes and derives the positions and parameters of the shadows for observers. It compares the results with previous studies and numerically obtains the curvature radii, vertical diameters, and horizontal diameters of the shadows. The findings suggest that under certain conditions, the shadows of these black holes are indistinguishable.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Emil T. Akhmedov, Kirill V. Bazarov
Summary: In this paper, we study a quantum real massive scalar field in the de Sitter-Schwarzschild spacetime background. To make analytical progress, we focus on the two-dimensional case, assuming that the situation in four dimensions will be similar conceptually. We assume the quantum field to be in a thermal state, described by the Planckian distribution for the exact modes in the given geometry. We approximately calculate the expectation value of the stress-energy tensor near the cosmological and black hole horizons. It is found that the geometry is strongly modified by the quantum fluctuations of the matter fields, due to the backreaction from quantum fields with a generic temperature.
Article
Astronomy & Astrophysics
Brayden R. Hull, Robert B. Mann
Summary: We demonstrate the existence of asymptotically de Sitter black holes of negative mass in Lovelock gravity. These black holes have horizon geometries with nonconstant curvature and are known as exotic black holes. We specifically study the case of Gauss-Bonnet gravity. We discuss the impact of transverse space geometry on the existence of black holes for both positive and negative mass solutions and provide closed form bounds for geometric parameters.
Article
Physics, Multidisciplinary
Eunice Omwoyo, Humberto Belich, Julio C. Fabris, Hermano Velten
Summary: Analytical solutions using Jacobi elliptic functions for bound and nearly bound photon orbits in Kerr-de Sitter and Kerr-de Sitter revisited spacetimes are derived in this paper. Analytic ray-tracing is conducted based on the obtained solutions in both spacetimes. Direct images, lensing rings and photon rings for equatorial disks are obtained for inclined locally static observers. The images corresponding to n = (2, 3) exhibit a significantly closer resemblance to the critical curve, showcasing the potential of these higher-order images as robust testing grounds for general relativity.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
Cheng-Yong Zhang, Peng Liu, Yun-Qi Liu, Chao Niu, Bin Wang
Summary: The study focuses on the fully nonlinear dynamics of spherically symmetric black hole spontaneous scalarization in Einstein-Maxwell-scalar theory. It is found that by adjusting the coupling function and black hole charge, the development and stabilization of hairy black holes can be influenced.
Article
Astronomy & Astrophysics
Ruth Gregory, Ian G. Moss, Naritaka Oshita, Sam Patrick
Summary: In this study, we investigate the evaporation process of a Kerr-de Sitter black hole with the Unruh-Hawking-like vacuum state and calculate the greybody factors for different particles. The presence of the cosmological constant dampens the amplification factor, approaching zero near the critical point where the Nariai and extremal limits merge. Despite the proximity to the critical point, gravitons exhibit more significant superradiance compared to photons and scalar particles, carrying angular momentum at a faster rate than mass energy decreases. The total entropy of the black hole and cosmological horizon increases with time, in accordance with the generalized second law of thermodynamics.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Physics, Multidisciplinary
Yubo Ma, Yang Zhang, Lichun Zhang, Yu Pan
Summary: The paper investigates the extended thermodynamics and entropic force of de Sitter space-time with charged Gauss-Bonnet black hole, providing insights into the characteristics of four-dimensional Gauss-Bonnet gravity. The results suggest that the interaction force between the black hole horizon and the cosmic horizon is composed of two parts, with one part proportional to the Gauss-Bonnet factor and the other part related to the ratio of the two horizons' positions.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Astronomy & Astrophysics
Bogeun Gwak
Summary: We investigate the weak cosmic censorship conjecture in extremal and near-extremal Kerr-Newman-(anti-)de Sitter black holes by scattering a massive scalar field with charge. While the black hole may exceed its extremal condition due to changes in its state caused by the scattering, it cannot be overcharged or overspun. The weak cosmic censorship conjecture is valid for any scalar field boundary conditions and is thermodynamically preferred for this scattering process.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Michael Joyce, Azrul Pohan
Summary: This article studies the separable analytical solution in standard perturbation theory for a generalized Einstein-de Sitter universe. The authors derive the corresponding kernels in Eulerian and Lagrangian perturbation theory, generalizing the canonical expressions. By relating cosmology-dependent corrections in perturbation theory to the analytic results for gEdS models, the calculation can be simplified and better understood.
Article
Physics, Particles & Fields
Sareh Eslamzadeh, Javad T. Firouzjaee, Kourosh Nozari
Summary: In this paper, we investigate the 4D Einstein-Gauss-Bonnet black hole and its thermodynamics. The study includes the analysis of three different asymptotic spacetimes and the correlation between emission modes and temperature. The results show interesting behaviors of temperature and emission in different spacetime backgrounds.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
Yubo Ma, Yang Zhang, Lichun Zhang, Liang Wu, Ying Gao, Shuo Cao, Yu Pan
Summary: The study of thermodynamics of de Sitter black holes in massive gravity space-time reveals that they do not meet the requirements of thermal equilibrium stability. However, by treating them as a thermodynamic system and discussing the effective thermodynamic quantities, we can explore the true reason behind the accelerating expansion of the universe.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Joy Das Bairagya, Kunal Pal, Kuntal Pal, Tapobrata Sarkar
Summary: This study examines the geometry of anti-de-Sitter (AdS) black hole thermodynamics in four dimensions, comparing it explicitly with normal fluid systems in the extended phase space formalism. The research shows how scalar curvature is proportional to thermodynamic volume for the parameter manifolds considered, and discusses how standard features in normal fluid systems impose restrictions on black hole parameters in extended phase space, potentially leading to physically invalid results in the current literature. A conjecture regarding the equality of correlation lengths of co-existing phases near criticality in charged AdS black hole backgrounds is also examined, with reasonable validity found.
Article
Astronomy & Astrophysics
M. Salti, O. Aydogdu, K. Sogut
Summary: This study mainly discusses the features of the PAdS black hole solution and its application as a stable configuration for dark energy stars. Through mathematical calculations and graphical analyses, important physical characteristics of the PAdS black hole are investigated.
GENERAL RELATIVITY AND GRAVITATION
(2021)