In this work,the optical appearance of an asymmetric thin-shell wormhole with a Bardeen profile is studied.To initiate the process,we need to construct an asymmetric thin-shell wormhole utilizing the cut-and-paste tec...In this work,the optical appearance of an asymmetric thin-shell wormhole with a Bardeen profile is studied.To initiate the process,we need to construct an asymmetric thin-shell wormhole utilizing the cut-and-paste technique proposed by Visser and subsequently ascertain its pertinent physical quantities such as the radius of the photon sphere and critical impact parameters for different values of magnetic charge g.Then,the effective potential and motion behavior of photons are also investigated within the framework of asymmetric thin-shell wormholes with a Bardeen profile.It can be found that the effective potential,ray trajectory,and azimuthal angle of the thin-shell wormhole exhibit a strong correlation with the mass ratio of black holes.By considering the accretion disk as the sole background light source,we observe additional photon rings and lensing bands in the optical appearance of the asymmetric thin-shell wormhole with a Bardeen profile compared to those exhibited by the Bardeen black hole.One can find that there is an increase in the size of the specific additional light bands with increasing magnetic charge g,which is different from the black hole case.These exceptionally luminous rings can serve as a robust criterion for the identification and characterization of the thin-shell wormhole spacetime.展开更多
We examine thermodynamic phase transition(PT)of the charged Gauss-Bonnet Ad S black hole(BH)by utilizing the shadow radius.In this system,we rescale the corresponding Gauss-Bonnet coefficientαby a factor of 1/(D-4),a...We examine thermodynamic phase transition(PT)of the charged Gauss-Bonnet Ad S black hole(BH)by utilizing the shadow radius.In this system,we rescale the corresponding Gauss-Bonnet coefficientαby a factor of 1/(D-4),and ensure thatαis positive to avoid any singularity problems.The equation derived for the shadow radius indicates that it increases as the event horizon radius increases,making it an independent variable for determining BH temperature.By investigating the PT curve in relation to shadows,we can observe that the shadow radius can be used as an alternative to the event horizon radius in explaining the phenomenon of BH PT.Furthermore,the results indicate that an increase in the parameterαcorresponds to a decrease in the temperature of the BH.By utilizing the relationship between the temperature and the shadow radius,it is possible to obtain the thermal profile of the Gauss-Bonnet AdS BH.It is evident that there is an N-type variation in temperature for pressures P<P_(c).Additionally,as the parameterαincreases,the region covered by shadow expands while the temperature decreases.The utilization of BH shadows as a probe holds immense significance in gaining a deeper understanding of BH thermodynamic behavior.展开更多
By considering the negative cosmological constant Λ as a thermodynamic pressure, we study the thermodynamics and phase transitions of the D-dimensional dyonic Ad S black holes(BHs) with quasitopological electromagnet...By considering the negative cosmological constant Λ as a thermodynamic pressure, we study the thermodynamics and phase transitions of the D-dimensional dyonic Ad S black holes(BHs) with quasitopological electromagnetism in Einstein–Gauss–Bonnet(EGB) gravity. The results indicate that the small/large BH phase transition that is similar to the van der Waals(vdW) liquid/gas phase transition always exists for any spacetime dimensions. Interestingly, we then find that this BH system exhibits a more complex phase structure in 6-dimensional case that is missed in other dimensions.Specifically, it shows for D = 6 that we observed the small/intermediate/large BH phase transitions in a specific parameter region with the triple point naturally appeared. Moreover, when the magnetic charge turned off, we still observed the small/intermediate/large BH phase transitions and triple point only in 6-dimensional spacetime, which is consistent with the previous results. However, for the dyonic Ad S BHs with quasitopological electromagnetism in Einstein–Born–Infeld(EBI) gravity, the novel phase structure composed of two separate coexistence curves observed by Li et al. [Phys. Rev. D105 104048(2022)] disappeared in EGB gravity. This implies that this novel phase structure is closely related to gravity theories, and seems to have nothing to do with the effect of quasitopological electromagnetism. In addition, it is also true that the critical exponents calculated near the critical points possess identical values as mean field theory. Finally, we conclude that these findings shall provide some deep insights into the intriguing thermodynamic properties of the dyonic Ad S BHs with quasitopological electromagnetism in EGB gravity.展开更多
Considering that the negative pressure of the accelerated expansion of the universe results from the cosmological constant or the dark energy quintessence,we use the dark energy quintessence to construct the"quin...Considering that the negative pressure of the accelerated expansion of the universe results from the cosmological constant or the dark energy quintessence,we use the dark energy quintessence to construct the"quintessential"phase space.In contrast to the previous discussion in which the cosmological constant is considered as the black hole(BH)phase transition pressure,in this analysis,we believe that the pressure results from quintessence.The characteristics of critical behavior,Gibbs free energy,and temperature behavior in quintessential phase space are investigated.We observe that the phase transition belongs to van der Waals phase transition within-1<ωq<-2/3.Ifωqis within(–2/3,–1/3),the phase transition loses the large BH phase transition characteristics,which is caused by the later stage of the phase transition being completely dominated by quintessence dark energy with negative pressure.These results suggest that the quintessential phase space can be constructed with the pressure from the thermal quintessence,and it can be used as a new probe to explore the thermodynamics of BHs.展开更多
We creatively employ the shadow radius to study the thermodynamics of a charged Ad S black hole with a nonlinear electrodynamics(NLED)term.First,the connection between the shadow radius and event horizon is constructe...We creatively employ the shadow radius to study the thermodynamics of a charged Ad S black hole with a nonlinear electrodynamics(NLED)term.First,the connection between the shadow radius and event horizon is constructed with the aid of the geodesic analysis.It turns out that the black hole shadow radius shows a positive correlation as a function of the event horizon radius.Then in the shadow context,we find that the black hole temperature and heat capacity can be presented by the shadow radius.Further analysis shows that the shadow radius can work similarly to the event horizon in revealing black hole phase transition process.In this sense,we construct the thermal profile of the charged Ad S black hole with inclusion of the NLED effect.In the P<Pc case,it is found that the N-type trend of the temperature given by the shadow radius is always consistent with that obtained by using the event horizon.Thus,we can conclude for the charged Ad S black hole that the phase transition process can be intuitively presented as the thermal profile in the shadow context.Finally,the effects of NLED are carefully analyzed.展开更多
The image of a black hole(BH)consists of direct and secondary images that depend on the observer position.We investigate the optical appearance of a Schwarzschild BH in the context of a string cloud to reveal how the...The image of a black hole(BH)consists of direct and secondary images that depend on the observer position.We investigate the optical appearance of a Schwarzschild BH in the context of a string cloud to reveal how the BH’s observable characteristics are influenced by the inclination angle,string cloud parameter,and impact parameter.Following Luminet’s work[Astron.Astrophys.75,228(1979)],we adopt a semi-analytic method to calculate the total bending angle of the light ray and derive the direct and secondary images of the Schwarzschild string cloud BH.Our results show that an increase in the inclination angle leads to a more pronounced separation of the images.We consider the gravitational redshift and present the redshift distribution of the direct image while illustrating the flux distribution.We observe that the direct image exhibits blueshift and redshift simultaneously,and the asymmetry of the flux distribution increases with the inclination angle.Finally,we obtain the Schwarzschild string cloud BH image via a numerical simulation,which provides an approximate illustration of the EHT resolution.展开更多
基金Supported by the National Natural Science Foundation of China(11903025)the Science and Technology Program of Sichuan Province,China(2023ZYD0023)the starting fund of China West Normal University(18Q062)。
文摘In this work,the optical appearance of an asymmetric thin-shell wormhole with a Bardeen profile is studied.To initiate the process,we need to construct an asymmetric thin-shell wormhole utilizing the cut-and-paste technique proposed by Visser and subsequently ascertain its pertinent physical quantities such as the radius of the photon sphere and critical impact parameters for different values of magnetic charge g.Then,the effective potential and motion behavior of photons are also investigated within the framework of asymmetric thin-shell wormholes with a Bardeen profile.It can be found that the effective potential,ray trajectory,and azimuthal angle of the thin-shell wormhole exhibit a strong correlation with the mass ratio of black holes.By considering the accretion disk as the sole background light source,we observe additional photon rings and lensing bands in the optical appearance of the asymmetric thin-shell wormhole with a Bardeen profile compared to those exhibited by the Bardeen black hole.One can find that there is an increase in the size of the specific additional light bands with increasing magnetic charge g,which is different from the black hole case.These exceptionally luminous rings can serve as a robust criterion for the identification and characterization of the thin-shell wormhole spacetime.
基金Project supported by the National Natural Science Foundation of China (Grant No.11903025)the starting fund of China West Normal University (Grant No.18Q062)+2 种基金the Sichuan Youth Science and Technology Innovation Research Team (Grant No.21CXTD0038)the Chongqing Science and Technology Bureau (Grant No.cstc2022ycjh-bgzxm0161)the Natural Science Foundation of Sichuan Province (Grant No.2022NSFSC1833)。
文摘We examine thermodynamic phase transition(PT)of the charged Gauss-Bonnet Ad S black hole(BH)by utilizing the shadow radius.In this system,we rescale the corresponding Gauss-Bonnet coefficientαby a factor of 1/(D-4),and ensure thatαis positive to avoid any singularity problems.The equation derived for the shadow radius indicates that it increases as the event horizon radius increases,making it an independent variable for determining BH temperature.By investigating the PT curve in relation to shadows,we can observe that the shadow radius can be used as an alternative to the event horizon radius in explaining the phenomenon of BH PT.Furthermore,the results indicate that an increase in the parameterαcorresponds to a decrease in the temperature of the BH.By utilizing the relationship between the temperature and the shadow radius,it is possible to obtain the thermal profile of the Gauss-Bonnet AdS BH.It is evident that there is an N-type variation in temperature for pressures P<P_(c).Additionally,as the parameterαincreases,the region covered by shadow expands while the temperature decreases.The utilization of BH shadows as a probe holds immense significance in gaining a deeper understanding of BH thermodynamic behavior.
基金supported by the National Natural Science Foundation of China (Grant No. 11903025)the Starting Fund of China West Normal University (Grant No. 18Q062)+2 种基金the Sichuan Science and Technology Program (Grant No. 2023ZYD0023)the Sichuan Youth Science and Technology Innovation Research Team (Grant No. 21CXTD0038)the Natural Science Foundation of Sichuan Province (Grant No. 2022NSFSC1833)。
文摘By considering the negative cosmological constant Λ as a thermodynamic pressure, we study the thermodynamics and phase transitions of the D-dimensional dyonic Ad S black holes(BHs) with quasitopological electromagnetism in Einstein–Gauss–Bonnet(EGB) gravity. The results indicate that the small/large BH phase transition that is similar to the van der Waals(vdW) liquid/gas phase transition always exists for any spacetime dimensions. Interestingly, we then find that this BH system exhibits a more complex phase structure in 6-dimensional case that is missed in other dimensions.Specifically, it shows for D = 6 that we observed the small/intermediate/large BH phase transitions in a specific parameter region with the triple point naturally appeared. Moreover, when the magnetic charge turned off, we still observed the small/intermediate/large BH phase transitions and triple point only in 6-dimensional spacetime, which is consistent with the previous results. However, for the dyonic Ad S BHs with quasitopological electromagnetism in Einstein–Born–Infeld(EBI) gravity, the novel phase structure composed of two separate coexistence curves observed by Li et al. [Phys. Rev. D105 104048(2022)] disappeared in EGB gravity. This implies that this novel phase structure is closely related to gravity theories, and seems to have nothing to do with the effect of quasitopological electromagnetism. In addition, it is also true that the critical exponents calculated near the critical points possess identical values as mean field theory. Finally, we conclude that these findings shall provide some deep insights into the intriguing thermodynamic properties of the dyonic Ad S BHs with quasitopological electromagnetism in EGB gravity.
基金supported by the National Natural Science Foundation of China(Grant No.11903025)the Natural Science Foundation of Sichuan Province,China(Grant No.2022NSFSC1833)。
文摘Considering that the negative pressure of the accelerated expansion of the universe results from the cosmological constant or the dark energy quintessence,we use the dark energy quintessence to construct the"quintessential"phase space.In contrast to the previous discussion in which the cosmological constant is considered as the black hole(BH)phase transition pressure,in this analysis,we believe that the pressure results from quintessence.The characteristics of critical behavior,Gibbs free energy,and temperature behavior in quintessential phase space are investigated.We observe that the phase transition belongs to van der Waals phase transition within-1<ωq<-2/3.Ifωqis within(–2/3,–1/3),the phase transition loses the large BH phase transition characteristics,which is caused by the later stage of the phase transition being completely dominated by quintessence dark energy with negative pressure.These results suggest that the quintessential phase space can be constructed with the pressure from the thermal quintessence,and it can be used as a new probe to explore the thermodynamics of BHs.
基金supported by the National Natural Science Foundation of China(Grant No.11903025)the Starting Fund of China West Normal University(Grant No.18Q062)+2 种基金the Sichuan Youth Science and Technology Innovation Research Team(Grant No.21CXTD0038)the Chongqing Science and Technology Bureau(Grant No.csts2022ycjh-bgzxm0161)the Natural Science Foundation of Sichuan Province(Grant No.2022NSFSC1833)。
文摘We creatively employ the shadow radius to study the thermodynamics of a charged Ad S black hole with a nonlinear electrodynamics(NLED)term.First,the connection between the shadow radius and event horizon is constructed with the aid of the geodesic analysis.It turns out that the black hole shadow radius shows a positive correlation as a function of the event horizon radius.Then in the shadow context,we find that the black hole temperature and heat capacity can be presented by the shadow radius.Further analysis shows that the shadow radius can work similarly to the event horizon in revealing black hole phase transition process.In this sense,we construct the thermal profile of the charged Ad S black hole with inclusion of the NLED effect.In the P<Pc case,it is found that the N-type trend of the temperature given by the shadow radius is always consistent with that obtained by using the event horizon.Thus,we can conclude for the charged Ad S black hole that the phase transition process can be intuitively presented as the thermal profile in the shadow context.Finally,the effects of NLED are carefully analyzed.
基金Supported by the National Natural Science Foundation of China(11903025)the Natural Science Foundation of Sichuan Province,China(2022NSFSC1833)。
文摘The image of a black hole(BH)consists of direct and secondary images that depend on the observer position.We investigate the optical appearance of a Schwarzschild BH in the context of a string cloud to reveal how the BH’s observable characteristics are influenced by the inclination angle,string cloud parameter,and impact parameter.Following Luminet’s work[Astron.Astrophys.75,228(1979)],we adopt a semi-analytic method to calculate the total bending angle of the light ray and derive the direct and secondary images of the Schwarzschild string cloud BH.Our results show that an increase in the inclination angle leads to a more pronounced separation of the images.We consider the gravitational redshift and present the redshift distribution of the direct image while illustrating the flux distribution.We observe that the direct image exhibits blueshift and redshift simultaneously,and the asymmetry of the flux distribution increases with the inclination angle.Finally,we obtain the Schwarzschild string cloud BH image via a numerical simulation,which provides an approximate illustration of the EHT resolution.
