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black holes in asymptotic safety with higher derivatives:accretion and stability analysis

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Chinese Physics C 2021年第7期45卷 293-304页

作者： Fabian H.Zuluaga Luis A.Sanchez Escuela de Fisica Universidad Nacional de ColombiaA.A.3840MedellinColombia

We review steady spherically symmetric accretion onto a renormalization group improved Schwarzschild space-time,which is a solution to an asymptotically safe theory(AS)containing high-derivative *** use a Hamiltonian dynamical system approach for the analysis of the accretion of four types of isothermal test fluids:ultra-stiff fluid,ultra-relativistic fluid,radiation fluid,and sub-relativistic *** important outcome of our study is that,contrary to the claim in a recent work,there are physical solutions for the accretion of an ultra-relativistic fluid in AS,which include subsonic,supersonic,and transonic ***,we study quantum corrections to the known stability of the accretion in general relativity(GR).To this end,we use a perturbative procedure based on the continuity equation with the mass accretion rate being the perturbed *** classes of perturbations are studied:standing and traveling *** find that quantum gravity effects either enhance or diminish the stability of the accretion depending on the type of test fluid and the radial distance to the central object.

关键词： asymptotic safety black holes accretion stability

Quantum Statistical Entropy of Non—extreme and Nearly Extreme black holes in Higher—Dimensional Space—Time

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Chinese Physics Letters 2003年第1期20卷 18-21页

作者：许殿彦 InstituteofMicroelectronicsandDepartmentofComputerScienceandTechnology PekingUniversityBeijing100871

The free energy and entropy of Reissner-Nordstrom black holes in higher-dimensional space-time are calculated by the quantum statistic method with a brick wall model. The space-time of the black holes is divided into three regions: region 1, (r > ro); region 2, (ro > r > ri); and region 3, (ri > r > 0), where ro is the radius of the outer event horizon, and ri is the radius of the inner event horizon. Detailed calculation shows that the entropy contributed by region 2 is zero, the entropy contributed by region 1 is positive and proportional to the outer event horizon area, the entropy contributed by region 3 is negative and proportional to the inner event horizon area. The total entropy contributed by all the three regions is positive and proportional to the area difference between the outer and inner event horizons. As ri approaches ro in the nearly extreme case, the total quantum statistical entropy approaches zero.

关键词： black holes

Brick Walls for Nonstationary black holes

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Chinese Physics Letters 2002年第12期19卷 1755-1758页

作者：黎忠恒赵峥等 DepartmentofPhysics ZhanjiangNormalCollegeZhanjiang524048 DepartmentofPhysics BeijingNormalUniversityBeijing100875

The validity condition of the brick-wall model is analysed in nonstationary space-time. It is shown that the model holds only in thin regions, only by using tortoise coordinates, near the event horizon of a slowly varying (quasi-stationary) black hole. The reason for the use of tortoise coordinates is that the stationary state solutions of quantum field equations in other coordinates do not exist for any region in nonstationary space-time. Meanwhile, the quantum corrections to the entropy of the Vaidya-Bonner black hole due to the spin fields are calculated in terms of the brick-wall model.

关键词： black holes

Weak gravitational lensing of quantum perturbed lukewarm black holes and cosmological constant effect

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Research in Astronomy and Astrophysics 2017年第6期17卷 17-36页

作者： Hossein Ghaffarnejad Mojtaba Amir Mojahedi Faculty of Physics Semnan University Semnan 35131-19111 Iran

The aim of the paper is to study weak gravitational lensing of quantum （perturbed） and classical lukewarm black holes （QLBHs and CLBHs respectively） in the presence of cosmological parameter A. We apply a numerical method to evaluate the deflection angle of bending light rays, image locations θ of sample sourceβ = π- 4, and corresponding magnifications μ. There are no obtained real values for Einstein ring locations θE（β = 0） for CLBHs but we calculate them for QLBHs. As an experimental test of our calculations, we choose mass M of 60 types of the most massive observed galactic black holes acting as a gravitational lens and study quantum matter field effects on the angle of bending light rays in the presence of cosmological constant effects. We calculate locations of non-relativistic images and corresponding magnifications. Numerical diagrams show that the quantum matter effects cause absolute values of the quantum deflection angle to be reduced with respect to the classical ones. The sign of the quantum deflection angle is changed with respect to the classical values in the presence of the cosmological constant. This means dominance of the anti-gravity counterpart of the cosmological horizon on the angle of bending light rays with respect to absorbing effects of 60 local types of the most massive observed black holes. Variations of the image positions and magnifications are negligible when increasing dimensionless cosmological constant ∈ = 16AM2 /2The deflection angle takes positive （negative） values for CLBHs （QLBHs） and they decrease very fast （slowly） by increasing the closest distance x0 of bending light ray and/or dimensionless cosmological parameter for sample giant black holes with 0.001 〈 ∈ 〈 0.01.

关键词： gravitational lensing weak - strong - micro - stars black holes

Charged AdS black holes with finite electrodynamics in 4D Einstein-Gauss-Bonnet gravity

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Chinese Physics C 2023年第3期47卷 282-290页

作者： Kimet Jusufi Physics Department State University of TetovoIlinden Street nn120oTetovoNorth Macedonia

Using a modified expression for the electric potential in the context of T-duality [Gaete and Nicolini, Phys. Lett. B, 2022], we obtained an exact charged solution within the 4D Einstein-Gauss-Bonnet (4D EGB) theory of gravity in the presence of a cosmological constant. We show that the solution also exists in the regularized 4D EGB theory. Moreover, we point out a correspondence between the black hole solution in the 4D EGB theory and the solution in the non-relativistic Horava–Lifshitz theory. The black hole solution is regular and free from singularity. As a special case, we derive a class of well known solutions in the literature.

关键词： black holes 4D Einstein-Gauss-Bonnet gravity T-duality exact solutions

Thermodynamic surface system of static black holes and area law

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Chinese Physics C 2016年第11期40卷 36-41页

作者：陈明黄永畅 Institute of Theoretical Physics Beijing University of TechnologyBeijing 100124China CCAST(World Lab.) P.O.Box 8730Beijing 100080China

We propose a new picture of black holes through a special holographic screen. This holographic screen contains all the degrees of freedom of a black hole. We find that this holographic screen is similar to the ordinary thermodynamic surface system. Meanwhile, through the ＂white-wall box＂ and the formula of sound velocity, we find some similarities between gravitons and photons. We further assume that such a holographic screen is a kind of Bose-Einstein condensate of gravitons. Through this assumption and those similarities, we finally get the area law of static black holes.

关键词： black holes holographic screen surface system "white-wall box" Bose-Einstein condensates area law

Linear instability of hairy black holes in Horndeski theory

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Chinese Physics C 2024年第7期48卷 253-258页

作者：张超朱涛 Beijing Key Laboratory of Optical Detection Technology for Oil and Gas Basic Research Center for Energy InterdisciplinaryCollege of ScienceChina University of Petroleum-BeijingBeijing 102249China Institute for Theoretical Physics and Cosmology Zhejiang University of TechnologyHangzhou 310023China United Center for Gravitational Wave Physics(UCGWP) Zhejiang University of TechnologyHangzhou 310023China

Horndeski theory constitutes the most general model of scalar-tensor *** has attracted much attention in recent years in relation with black holes,celestial dynamics,stability analysis,*** is important to note that,for certain subclasses of Horndeski models,one can obtain analytic solutions for the background *** facilitates the investigation of the corresponding stability problems in *** particular,we aim to determine the constraints to the model or theory under which the stability conditions can be *** this study,we focused on a subclass of Horndeski theory and a set of analytic background *** addition,the odd-parity gravitational perturbation and 2nd-order Lagrangian were *** careful analysis,the instability was identified within the neighborhood of the event *** allows exclusion of a specific geometry for the *** an instability is implanted in the structure of the corresponding Lagrangian and is not erased by simply adding numerical constraints on the coupling *** a starting point of our research,the current study provides insights for further exploration of the Horndeski theory.

关键词： black holes black hole perturbations scalar-tensor theories Horndeski theory

Null geodesics,quasinormal modes,and thermodynamic phase transition for charged black holes in asymptotically flat and dS spacetimes

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Chinese Physics C 2020年第11期44卷 220-231页

作者： Shao-Wen Wei Yu-Xiao Liu Institute of Theoretical Physics&Research Center of Gravitation Lanzhou UniversityLanzhou 730000China Department of Physics and Astronomy University of WaterlooWaterlooOntarioN2L 3G1Canada

A numerical study has indicated that there exists a relation between the quasinormal modes and the Davies point for a black *** this paper,we analytically study this relation for charged Reissner-Nordstrom black holes in asymptotically flat and de Sitter(dS)spacetimes in the eikonal limit,under which the quasinormal modes can be obtained from the null geodesics using the angular velocity Ω and the Lyapunov exponentλof the photon *** in asymptotically flat and dS spacetimes,we observe spiral-like shapes in the complex quasinormal mode ***,the starting point of the shapes does not coincide with the Davies ***,we find a new relation in which the Davies point exactly meets the maximum temperature T in the T-Ω and T-λ *** a higher-dimensional asymptotically flat spacetime,although there is no spiral-like shape,such a relation still ***,we provide a new relation between black hole thermodynamics and dynamics in the eikonal *** this relation,we can test the thermodynamic property of a black hole using the quasinormal modes.

关键词： black holes phase transition photon sphere

Thermodynamics in rotating anti-de Sitter black holes with massive scalar field in three dimensions

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Chinese Physics C 2020年第12期44卷 240-247页

作者： Bogeun Gwak Division of Physics and Semiconductor Science Dongguk UniversitySeoul 04620Republic of Korea

We investigated the tendency in the variations of CFT2 when a rotating AdS3 black hole changes because of the fluxes transferred by the scattering of a massive scalar field according to the anti-de Sitter(AdS)/conformal field theory(CFT)*** conserved quantities of the black hole are definitely constrained by the extremal ***,the laws of thermodynamics provide a direction for the changes in the conserved ***,the black hole cannot be extremal under the scattering;this is naturally *** to the relationship between the rotating AdS3 black hole and dual CFT2,we find that such changes in the black hole constrain the variations in the eigenstates of dual ***,the tendency in the variations is closely related to the laws of thermodynamics.

关键词： black holes thermodynamics AdS/CFT correspondence