Article
Astronomy & Astrophysics
Joao P. B. Brito, Rafael P. Bernar, Luis C. B. Crispino
Summary: In this study, we investigate the scalar radiation emitted by a source orbiting a Schwarzschild-anti-de Sitter black hole in circular geodesics. We compare the emitted power with that in other spacetimes and find different patterns of enhancement depending on the multipole modes.
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
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
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
Peter Taylor, Cormac Breen
Summary: This study focuses on the quantum scalar field on the classical background of an asymptotically anti-de Sitter black hole and the backreaction the field's stress-energy tensor induces on the black hole geometry. By using simple analytical approximations to calculate the stress-energy tensor, reasonable approximations to the first-order quantum backreaction on the geometry of asymptotically anti-de Sitter black holes are provided.
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)
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
Physics, Multidisciplinary
Zhen-Ming Xu, Bin Wu, Wen-Li Yang
Summary: This study used Kramer's escape rate method to investigate the intensity of the phase transition between small and large black hole states. The results show that the phase transition of charged anti-de Sitter (AdS) black holes from small to large presents serious asymmetric features, and the process is dominated by the transition from a small to a large black hole. This study filled a research gap in stochastic process analysis of the first-order phase transition rate in AdS black holes.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2023)
Article
Physics, Particles & Fields
H. S. Vieira
Summary: This study investigates the interaction between quantum scalar particles and the gravitational field of a generalized black hole with an f(R) global monopole using the f(R) theory of gravity. The separability of the Klein-Gordon equation with a non-minimal coupling is examined, and both massless and massive cases for a conformal coupling are discussed. Physical phenomena related to the asymptotic behavior of the radial function, such as black hole radiation, quasibound states, and wave eigenfunctions, are also investigated.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Abhishek Mathur, Sumati Surya, X. Nomaan
Summary: In this study, we calculate the manifestly covariant entanglement entropy S for a massive and massless minimally coupled free Gaussian scalar field on the de Sitter horizon and Schwarzschild de Sitter horizons, respectively. The calculations show that S for the mixed state is independent of the effective mass and matches the results obtained by Higuchi and Yamamoto. By using a cut-off in the angular modes, it is found that S is proportional to the area of the respective horizons.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Article
Physics, Particles & Fields
Iarley P. Lobo, Luis C. N. Santos, V. B. Bezerra, J. P. Morais Graca, H. Moradpour
Summary: The study focused on the effect of Planck-scale modified radiation equation of state on Reissner-Nodstrom-anti-de Sitter black hole inspired by Kiselev's ansatz. Deformed thermodynamic quantities were identified, and phase transitions and black holes as heat engines were described for the Carnot and square cycles. The non-trivial differences between linear and quadratic Planck-scale corrections were discussed in detail.
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
Astronomy & Astrophysics
Grigory E. Volovik
Summary: This paper investigates the origin of the double Hawking temperature in quantum tunneling and Hawking radiation, and its application in black hole horizon and de Sitter spacetime. In the black hole horizon, the double Hawking temperature is attributed to two contributions combined to produce the Hawking temperature. In de Sitter spacetime, the double Hawking temperature describes the creation of entangled pairs, while the local temperature describes the creation of non-entangled particles.
Article
Astronomy & Astrophysics
Cristiano Germani
Summary: According to Hawking's calculation, the correlation functions in a black hole decay exponentially over time. This paper demonstrates that by using the steepest descent expansion on the classical saddle point (the black hole background), the early time decay can be transformed into a late time growth, consistent with information retrieval.
Article
Astronomy & Astrophysics
Cesar Gomez, Raul Jimenez
Summary: In this article, the previous work on how the underlying primordial scaling law is implemented in the dS quantum Fisher information is summarized. The results show that, without any qdS input, the value of the spectral index ns is determined to be 0.9672 at large scales, and a small running value is predicted that is compatible with current experimental results.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Physics, Particles & Fields
Nelson R. F. Braga, Luiz F. Ferreira
EUROPEAN PHYSICAL JOURNAL C
(2017)
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Roldao da Rocha
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Luiz F. Ferreira
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Luiz F. Ferreira, Roldao da Rocha
Article
Physics, Particles & Fields
Nelson R. F. Braga, Luiz F. Ferreira
JOURNAL OF HIGH ENERGY PHYSICS
(2019)
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Luiz F. Ferreira
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Rodrigo da Mata
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Rodrigo da Mata
Article
Astronomy & Astrophysics
Nelson R. F. Braga, O. C. Junqueira
Summary: The confinement/deconfinement transition in the holographic AdS/QCD approach is associated with the Hawking-Page transition from a thermal anti-de Sitter (AdS) space to an AdS black hole. In the case of the hard wall model, the thermal transition occurs in planar AdS due to the introduction of an infrared cut-off. By investigating the configuration entropy (CE) of asymptotically AdS geometries, a proportional relationship between CE and log(T) is found, indicating a simple connection between configuration and thermodynamic entropies.
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Octavio C. Junqueira
Summary: The study uses configuration entropy to investigate the stability of the soft wall background as a function of temperature, revealing a consistent relationship with black hole instability in anti-de Sitter space. Another interesting finding is that the regularized energy density exhibits behavior similar to the Wien law.
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Yan F. Ferreira, Luiz F. Ferreira
Summary: Heavy vector mesons produced in a heavy ion collision are important for understanding the quark gluon plasma, and investigating their properties in a thermal medium with a magnetic field background can provide interesting and significant insights.
Article
Astronomy & Astrophysics
Luis A. H. Mamani, Defu Hou, Nelson R. F. Braga
Summary: This work investigates the melting of charmonium states within a holographic QCD model. The study finds that charmonium melts at temperatures above the confinement/deconfinement temperature and that the chemical potential speeds up the melting process. It also analyzes the perturbation equations in the hydrodynamic limit and discusses the emergence of a new mode with specific properties.
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Luiz F. Faulhaber, Octavio C. Junqueira
Summary: This study investigates the influence of rotation of the medium on the confinement/deconfinement transition temperature Tc of the quark gluon plasma using holographic AdS/QCD models. It is found that as the rotational velocity increases, Tc decreases, following the expression Tc(v) = Tc(0)/gamma(v), where gamma(v) is the Lorentz factor.
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Rodrigo da Mata
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.