this paper,we base our analysis on the assumption that the existence of a photon sphere is an intrinsic characteristic of any ultra-compact gravitational structure with spherical symmetry.Utilizing the concept of a to...this paper,we base our analysis on the assumption that the existence of a photon sphere is an intrinsic characteristic of any ultra-compact gravitational structure with spherical symmetry.Utilizing the concept of a topological photon sphere,we categorize the behaviors of various gravitational models based on the structure of their photon spheres.This innovative approach enables us to define boundaries for black hole parameters,subsequently enabling us to classify the model as either a black hole or naked singularity.We demonstrate that the presence of this interplay between the gravitational structure and the existence of a photon sphere is a unique advantage that can be utilized from both perspectives.Our observations indicate that a gravitational model typically exhibits the behavior ofa horizonless structure(or naked singularity)when a minimum effective potential(a stable photon sphere)appears within the studied spacetime region.Additionally,in this study,we investigate the effect of this structure on the behavior of the photon sphere by selecting models that are affected by Perfect Fluid Dark Matter(PFDM).Finally,by analyzing a model with multiple event horizons,we show that the proposed method remains applicable evenin suchscenarios.展开更多
In this paper,we investigate the topological charge and conditions for the existence of the photon sphere in Kiselev-anti-de Sitter(AdS)black holes within f(R,T)gravity.Furthermore,we establish their topological class...In this paper,we investigate the topological charge and conditions for the existence of the photon sphere in Kiselev-anti-de Sitter(AdS)black holes within f(R,T)gravity.Furthermore,we establish their topological classifications.We employ two different methods based on Duan's topological current p-mapping theory viz analysis of temperature and the generalized Helmholtz free energy methods to study the topological classes of our black hole.Considering this black hole,we discuss the critical and zero points(topological charges and topological numbers)for different parameters.Our findings reveal that the Kiselev parameter o and f(R,T)gravity parameter y influence the number of topological charges of black holes,providing novel insights into topological classifications.We observe that for given values of the free parameters,total topological charges(Q_(total)=-1)exist for the T method and total topological numbers(ω=+1)for the generalized Helmholtz free energy method.Our research findings elucidate that,in contrast to the scenario in whichω=1/3,in other cases,increasing y increases the number of total topological charges for the black hole.Interestingly,for the phantom field(ω=-4/3),we observe that decreasingγincreases the number of topological charges.Additionally,we study the results for the photon sphere.The studied models reveal that the simultaneous presence ofγandωeffectively expands the permissible range forγ.In other words,the model can exhibit black hole behavior over a larger domain.Additionally,we observe that with the stepwise reduction ofγ,the region covered by singularity diminishes and becomes more restricted.However,an interesting point about all three ranges is the elimination of the forbidden region in this model.In other words,this model and the investigated areas appear to have no region in which both theφand metric functions simultaneously lack solutions.Additionally,we fully check the curvatures singularities and energy conditions for the mentioned black hole.展开更多
We search for a possible relationship between weak gravity conjecture(WGC)and conformal field theory(CFT)in hyperscaling violating and Kerr-Newman-AdS black holes.We deal with the critical points of the black hole sys...We search for a possible relationship between weak gravity conjecture(WGC)and conformal field theory(CFT)in hyperscaling violating and Kerr-Newman-AdS black holes.We deal with the critical points of the black hole systems using the correlation function introduced in CFT and discuss WGC conditions using the imaginary part of the energy obtained from the critical points and their poles.Under the assumptions z=1,d=1,andθ→0-,we link WGC to hyperscaling violating black holes owing to the existence of rHvalues larger and smaller than one.For the second black hole system,we study the conditions of WGC for Kerr-Newman-AdS black holes using rotation and radius parameters.Then,we show that the conditions of WGC are satisfied when the charged particle near the hyperscaling violating and Kerr-Newman black holes is 1/a with a ratio a/l《1.展开更多
文摘this paper,we base our analysis on the assumption that the existence of a photon sphere is an intrinsic characteristic of any ultra-compact gravitational structure with spherical symmetry.Utilizing the concept of a topological photon sphere,we categorize the behaviors of various gravitational models based on the structure of their photon spheres.This innovative approach enables us to define boundaries for black hole parameters,subsequently enabling us to classify the model as either a black hole or naked singularity.We demonstrate that the presence of this interplay between the gravitational structure and the existence of a photon sphere is a unique advantage that can be utilized from both perspectives.Our observations indicate that a gravitational model typically exhibits the behavior ofa horizonless structure(or naked singularity)when a minimum effective potential(a stable photon sphere)appears within the studied spacetime region.Additionally,in this study,we investigate the effect of this structure on the behavior of the photon sphere by selecting models that are affected by Perfect Fluid Dark Matter(PFDM).Finally,by analyzing a model with multiple event horizons,we show that the proposed method remains applicable evenin suchscenarios.
文摘In this paper,we investigate the topological charge and conditions for the existence of the photon sphere in Kiselev-anti-de Sitter(AdS)black holes within f(R,T)gravity.Furthermore,we establish their topological classifications.We employ two different methods based on Duan's topological current p-mapping theory viz analysis of temperature and the generalized Helmholtz free energy methods to study the topological classes of our black hole.Considering this black hole,we discuss the critical and zero points(topological charges and topological numbers)for different parameters.Our findings reveal that the Kiselev parameter o and f(R,T)gravity parameter y influence the number of topological charges of black holes,providing novel insights into topological classifications.We observe that for given values of the free parameters,total topological charges(Q_(total)=-1)exist for the T method and total topological numbers(ω=+1)for the generalized Helmholtz free energy method.Our research findings elucidate that,in contrast to the scenario in whichω=1/3,in other cases,increasing y increases the number of total topological charges for the black hole.Interestingly,for the phantom field(ω=-4/3),we observe that decreasingγincreases the number of topological charges.Additionally,we study the results for the photon sphere.The studied models reveal that the simultaneous presence ofγandωeffectively expands the permissible range forγ.In other words,the model can exhibit black hole behavior over a larger domain.Additionally,we observe that with the stepwise reduction ofγ,the region covered by singularity diminishes and becomes more restricted.However,an interesting point about all three ranges is the elimination of the forbidden region in this model.In other words,this model and the investigated areas appear to have no region in which both theφand metric functions simultaneously lack solutions.Additionally,we fully check the curvatures singularities and energy conditions for the mentioned black hole.
文摘We search for a possible relationship between weak gravity conjecture(WGC)and conformal field theory(CFT)in hyperscaling violating and Kerr-Newman-AdS black holes.We deal with the critical points of the black hole systems using the correlation function introduced in CFT and discuss WGC conditions using the imaginary part of the energy obtained from the critical points and their poles.Under the assumptions z=1,d=1,andθ→0-,we link WGC to hyperscaling violating black holes owing to the existence of rHvalues larger and smaller than one.For the second black hole system,we study the conditions of WGC for Kerr-Newman-AdS black holes using rotation and radius parameters.Then,we show that the conditions of WGC are satisfied when the charged particle near the hyperscaling violating and Kerr-Newman black holes is 1/a with a ratio a/l《1.
