In this study,we present a comprehensive analysis of a modified Frolov black hole(BH)model that incorporates two types of topological defects,a global monopole(GM)and a cloud of strings(CS).This composite BH solution ...In this study,we present a comprehensive analysis of a modified Frolov black hole(BH)model that incorporates two types of topological defects,a global monopole(GM)and a cloud of strings(CS).This composite BH solution is examined from multiple theoretical perspectives to explore the impact of these modifications on the BH's geometric,thermodynamic and dynamical properties.We begin by studying the geometrical optics of the spacetime,focusing on the motion of null geodesics.Key features,such as the effective potential,photon sphere,the force acting on photons and the stability of circular photon orbits,are analyzed in detail.Our results show that the presence of GM and CS significantly affects the spacetime geometry and photon dynamics.In addition,the thermodynamic behavior of the modified BH is also investigated.We derive essential quantities such as the Hawking temperature and entropy,demonstrating how the inclusion of GM and CS leads to deviations from the standard thermodynamic relations observed in classical BH solutions.These deviations may offer valuable insights into quantum gravity and the role of topological defects in BH physics.Furthermore,we examine the BH shadow as an observational signature of the underlying geometry.Our analysis shows that the Frolov parameter tends to reduce the apparent size of the shadow,while the presence of topological defects,particularly GM and CS,enlarges it.In addition,we investigate the perturbative dynamics of the BH by studying both scalar(spin-0),fermionic(spin-1/2)and electromagnetic(spin-1)fields through the massless Klein-Gordon and Maxwell equations,respectively.Using the Wentzel-Kramers-Brillouin approximation,we compute the quasinormal modes(QNMs)for scalar and electromagnetic field perturbations.The results confirm the stability of the BH under small perturbations and show that the QNM frequencies and damping rates are strongly influenced by the Frolov parameter,electric charge,GM and CS.展开更多
A semiclassical particle moving near the horizon of a Schwarzschild black hole is chaotic,and its Lyapunov exponent saturates the chaos bound proposed by Maldacena,Shenker,and Stanford,with the temperature being the H...A semiclassical particle moving near the horizon of a Schwarzschild black hole is chaotic,and its Lyapunov exponent saturates the chaos bound proposed by Maldacena,Shenker,and Stanford,with the temperature being the Hawking temperature.Motivated by this,we consider the Lyapunov exponents of scalar and spinor fields in Schwarzschild spacetime by calculating their out-of-time-ordered commutators along the radial direction.Numerically,we find that the Lyapunov exponent of the scalar field is smaller than that of the spinor field.They are mainly contributed by the bound states near the horizon and lie below the chaos bound.展开更多
In this study,we explore a spherically symmetric charged black hole(BH)with a negative cosmological constant under the influence of a Kalb-Ramond field background.We compute the photon sphere and shadow radii,validati...In this study,we explore a spherically symmetric charged black hole(BH)with a negative cosmological constant under the influence of a Kalb-Ramond field background.We compute the photon sphere and shadow radii,validating our findings using observational data from the Event Horizon Telescope,with a particular emphasis on the shadow images of Sagittarius A^(*).Furthermore,we investigate the greybody factors,emission rate,and partial absorption cross section.It is shown that the Lorentz-violating parameter l has an important effect on the absorption cross section.Our analysis also includes an examination of the topological charge,temperature-dependent topology,and generalized free energy.In particular,we regard the AdS charged BH with an antisymmetric tensor background as a topological defect in the thermodynamic space,then the system has the same topological classification to the charged Reissner-Nordström-AdS BH.展开更多
This study examines the effect of charge on physical features of a gravastar model in the framework of Rastall gravity.A gravastar is an alternative model to a black hole consisting of three separate regions:the inner...This study examines the effect of charge on physical features of a gravastar model in the framework of Rastall gravity.A gravastar is an alternative model to a black hole consisting of three separate regions:the inner sector,the intermediate shell and the outer sector.Different values of the barotropic equation of state(EoS)parameter provide the mathematical basis for these regions.Field equations(FEs)are initially developed for a spherically symmetric spacetime coupled with charged matter distribution.We then use the temporal component of TolmanⅣspacetime to formulate the radial metric potential for both the inner region and intermediate shell.We also apply the matching criteria to ensure smooth matching of exterior and interior spacetimes so that the constants resulting from integrations can be determined.Afterwards,we explore various physical properties of the developed gravastar model such as the proper length,entropy,energy,and others to analyze how shell thickness and charge affect them.It is concluded that,in the background of Rastall theory,a gravastar model exists and serves as a viable alternative to the black hole.展开更多
Based on the idea of treating the anti de Sitter(AdS)radius as a fixed parameter,we study the thermodynamics and topology of d-dimensional charged AdS black holes in the restricted phase space utilizing Visser's h...Based on the idea of treating the anti de Sitter(AdS)radius as a fixed parameter,we study the thermodynamics and topology of d-dimensional charged AdS black holes in the restricted phase space utilizing Visser's holographic approach.For the charged black hole with a cloud of strings and quintessence in the higher-dimensional spacetimes with d=(4,5,6),we demonstrate that the topological number remains invariant within the same canonical ensemble;however,a distinct topological number emerges in the grand canonical ensemble for the same black hole system.Notably,these results are independent of the dimension d and other related parameters.The formalism known as restricted phase space thermodynamics is checked in detail and some interesting thermodynamic behavior is revealed in the example case of d-dimensional charged AdS black holes with a cloud of strings and quintessence.This research lays the foundation for establishing a universal framework of restricted phase space thermodynamics and investigating its fundamental thermodynamic properties.展开更多
自2017年发射以来,慧眼硬X射线调制望远镜(Insight Hard X-ray Modulation Telescope,InsightHXMT)凭借着宽能段、大有效面积和高观测频率的优势,已经成为吸积X射线脉冲星研究领域中最重要的天文卫星之一.它在回旋吸收线和吸积物理研究...自2017年发射以来,慧眼硬X射线调制望远镜(Insight Hard X-ray Modulation Telescope,InsightHXMT)凭借着宽能段、大有效面积和高观测频率的优势,已经成为吸积X射线脉冲星研究领域中最重要的天文卫星之一.它在回旋吸收线和吸积物理研究中取得了重要进展,主要包括探测到高能回旋吸收线、揭示回旋线能量的演化和观测到辐射压主导的吸积盘.展开更多
基金financial support from EMU, TÜBİTAK, ANKOS and SCOAP3
文摘In this study,we present a comprehensive analysis of a modified Frolov black hole(BH)model that incorporates two types of topological defects,a global monopole(GM)and a cloud of strings(CS).This composite BH solution is examined from multiple theoretical perspectives to explore the impact of these modifications on the BH's geometric,thermodynamic and dynamical properties.We begin by studying the geometrical optics of the spacetime,focusing on the motion of null geodesics.Key features,such as the effective potential,photon sphere,the force acting on photons and the stability of circular photon orbits,are analyzed in detail.Our results show that the presence of GM and CS significantly affects the spacetime geometry and photon dynamics.In addition,the thermodynamic behavior of the modified BH is also investigated.We derive essential quantities such as the Hawking temperature and entropy,demonstrating how the inclusion of GM and CS leads to deviations from the standard thermodynamic relations observed in classical BH solutions.These deviations may offer valuable insights into quantum gravity and the role of topological defects in BH physics.Furthermore,we examine the BH shadow as an observational signature of the underlying geometry.Our analysis shows that the Frolov parameter tends to reduce the apparent size of the shadow,while the presence of topological defects,particularly GM and CS,enlarges it.In addition,we investigate the perturbative dynamics of the BH by studying both scalar(spin-0),fermionic(spin-1/2)and electromagnetic(spin-1)fields through the massless Klein-Gordon and Maxwell equations,respectively.Using the Wentzel-Kramers-Brillouin approximation,we compute the quasinormal modes(QNMs)for scalar and electromagnetic field perturbations.The results confirm the stability of the BH under small perturbations and show that the QNM frequencies and damping rates are strongly influenced by the Frolov parameter,electric charge,GM and CS.
基金supported by the National Natural Science Foundation of China with Grants No.12174067 and No.11804223。
文摘A semiclassical particle moving near the horizon of a Schwarzschild black hole is chaotic,and its Lyapunov exponent saturates the chaos bound proposed by Maldacena,Shenker,and Stanford,with the temperature being the Hawking temperature.Motivated by this,we consider the Lyapunov exponents of scalar and spinor fields in Schwarzschild spacetime by calculating their out-of-time-ordered commutators along the radial direction.Numerically,we find that the Lyapunov exponent of the scalar field is smaller than that of the spinor field.They are mainly contributed by the bound states near the horizon and lie below the chaos bound.
基金supported by the Doctoral Foundation of Zunyi Normal University of China (BS [2022] 07)Fundação de Apoio à Pesquisa do Estado da Paraíba (FAPESQ)+5 种基金Conselho Nacional de Desenvolvimento Cientíıfico e Tecnológico (CNPq)-[150891/2023-7] for the financial supportsupported by the Q-CAYLE project, funded by the European Union-Next Generation UE/MICIU/Plan de Recuperacion, Transformacion y Resiliencia/Junta de Castilla y Leon (PRTRC17.11)by project PID2023-148409NB-I00, funded by MICIU/AEI/10.13039/501100011033Financial support of the Department of Education of the Junta de Castilla y LeonFEDER FundsExcellence project Fo S UHK 2203/2025-2026 for the financial support
文摘In this study,we explore a spherically symmetric charged black hole(BH)with a negative cosmological constant under the influence of a Kalb-Ramond field background.We compute the photon sphere and shadow radii,validating our findings using observational data from the Event Horizon Telescope,with a particular emphasis on the shadow images of Sagittarius A^(*).Furthermore,we investigate the greybody factors,emission rate,and partial absorption cross section.It is shown that the Lorentz-violating parameter l has an important effect on the absorption cross section.Our analysis also includes an examination of the topological charge,temperature-dependent topology,and generalized free energy.In particular,we regard the AdS charged BH with an antisymmetric tensor background as a topological defect in the thermodynamic space,then the system has the same topological classification to the charged Reissner-Nordström-AdS BH.
文摘This study examines the effect of charge on physical features of a gravastar model in the framework of Rastall gravity.A gravastar is an alternative model to a black hole consisting of three separate regions:the inner sector,the intermediate shell and the outer sector.Different values of the barotropic equation of state(EoS)parameter provide the mathematical basis for these regions.Field equations(FEs)are initially developed for a spherically symmetric spacetime coupled with charged matter distribution.We then use the temporal component of TolmanⅣspacetime to formulate the radial metric potential for both the inner region and intermediate shell.We also apply the matching criteria to ensure smooth matching of exterior and interior spacetimes so that the constants resulting from integrations can be determined.Afterwards,we explore various physical properties of the developed gravastar model such as the proper length,entropy,energy,and others to analyze how shell thickness and charge affect them.It is concluded that,in the background of Rastall theory,a gravastar model exists and serves as a viable alternative to the black hole.
基金supported by the Natural Science Foundation of Shanxi Province(202303021211180)the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices(KF202403)。
文摘Based on the idea of treating the anti de Sitter(AdS)radius as a fixed parameter,we study the thermodynamics and topology of d-dimensional charged AdS black holes in the restricted phase space utilizing Visser's holographic approach.For the charged black hole with a cloud of strings and quintessence in the higher-dimensional spacetimes with d=(4,5,6),we demonstrate that the topological number remains invariant within the same canonical ensemble;however,a distinct topological number emerges in the grand canonical ensemble for the same black hole system.Notably,these results are independent of the dimension d and other related parameters.The formalism known as restricted phase space thermodynamics is checked in detail and some interesting thermodynamic behavior is revealed in the example case of d-dimensional charged AdS black holes with a cloud of strings and quintessence.This research lays the foundation for establishing a universal framework of restricted phase space thermodynamics and investigating its fundamental thermodynamic properties.
文摘自2017年发射以来,慧眼硬X射线调制望远镜(Insight Hard X-ray Modulation Telescope,InsightHXMT)凭借着宽能段、大有效面积和高观测频率的优势,已经成为吸积X射线脉冲星研究领域中最重要的天文卫星之一.它在回旋吸收线和吸积物理研究中取得了重要进展,主要包括探测到高能回旋吸收线、揭示回旋线能量的演化和观测到辐射压主导的吸积盘.
