arXiv subjects

Xiao-Xiong Zeng

Publications and source records attributed to Xiao-Xiong Zeng.

At least 73 records · Page 4Linked to original sources

arXiv2023

Holographic Einstein rings of a black hole with a global monopole

The global monopole solutions which give rise to quite unusual physical phenomena have captured considerable attention. In this paper, we study the Einstein ring of the spherically symmetric AdS black hole solution with a global monopole based on the AdS/CFT correspondence. With the help of the given response function of the QFT on the boundary, we construct the holographic images of the black hole in the bulk. The Einstein rings on the images can be clearly observed. The holographic ring always appears with the concentric stripe surrounded when the observer located at the north pole, and an extremely bright ring when the observer is at the position of the photon sphere of the black hole. With the change of the observation position, this ring will change into a luminosity-deformed ring, or light points. Furthermore, we show that the monopole parameter has an effect on the brightness and the position of Einstein ring. All these results imply that the holographic images can be used as an effective tool to distinguish different types of black holes for fixed wave source and optical system.

hep-th↗

arXiv2023

Holographic Einstein rings of a Gauss-Bonnet AdS black hole

Based on the AdS/CFT correspondence, we studied the holographic Einstein images of a Gauss-Bonnet AdS black hole in the bulk from a given response function on AdS boundary. For the absolute amplitude of total response function, it shows that there always exists the interference pattern as the scalar wave passed through the black hole. And, the absolute amplitude depends closely on the properties of Gaussian source and spacetime geometry. More importantly, we also find that the holographic images always appears as a ring with the concentric stripe surrounded when the observer located at the north pole. At other positions, this ring will change into a luminosity-deformed ring, or two light points. In addition, the effects of Gauss-Bonnet parameter $α$, wave source and optical system on the holographic images have been carefully addressed throughout of paper. Finally, we conclude that the holographic images in different types of black holes with some different features may shed some deep insight on the existence of a gravity dual for a given material.

gr-qc↗

arXiv2022

Holographic Einstein Ring of a Charged AdS Black Hole

Taking into account that the real quantum materials are engineered generically at a finite chemical potential, we investigate the Einstein ring structure for the lensed response of the complex scalar field as a probe wave on the charged AdS black hole in the context of AdS/CFT. On the one hand, we find that the resulting Einstein ring radius has no variation with the chemical potential, which is similar to the behavior for the weakly interacting quantum system. On the other hand, not only can such a ring exist well within the screen, but also the temperature dependence of its radius exhibits a distinct feature in the sense that it displays an appreciable increase at low temperatures while the ring keeps unchanged right at the edge of the screen for the weakly interacting system. Note that such a Einstein ring emerges in the large frequencies and can be well captured by the photon sphere away from the black hole horizon in the geometric optics approximation, thus such a distinct feature may be regarded as a universal behavior associated with the high energy modes of the strongly coupled system which has a gravity dual.

hep-th↗

arXiv2022

QED and accretion flow models effect on optical appearance of Euler-Heisenberg black holes

Taking the quantum electrodynamics (QED) effect into account, we investigate the geometrical-optics appearance of the Euler-Heisenberg (EH) black hole (BH) under the different accretion flows context, which depends on the BH space-time structure and different sources of light. The more significant magnetic charge leads to the smaller shadow radius for the EH BH, while the different values of the EH parameter do not ruin it. Different features of the corresponding two-dimensional shadow images are derived for the three optically thin accretion flow models. It is shown that the total observed intensity in the static spherical accretion flow scenario leads than that of the infalling spherical accretion flow under same parameters, but the size and position of the EH BH shadows do not change in both of these accretions flows, implying that the BH shadow size depends on the geometric space-time and the shadows luminosities rely on the accretion flow morphology. Of particular interest is that a thin disk accretion model illuminated the BH, we found that the contribution of the lensing ring to the total observed flux is less than 5\%, and the photon ring is less than 2\%, indicating that the direct emission dominates the optical appearance of the EH BH. It is also believed that the optical appearance of the BH image depends on the accretion disk radiation position in this scenario, which can serve as a probe for the disk structure around the active galactic nucleus (AGN) of M87^{*} like.

gr-qc↗

arXiv2022

The Optical Appearance of Charged Four-Dimensional Gauss-Bonnet Black Hole with Strings Cloud and Non-Commutative Geometry Surrounded by Various Accretions Profiles

Thanks for the releasing image of supermassive black holes (BHs) by the event horizon telescope (EHT) at the heart of the $M87$ galaxy. After the discovery of this mysterious object, scientists paid attention to exploring the BH shadow features under different gravitational backgrounds. In this scenario, we study the light rings and observational properties of BH shadow surrounded by different accretion flow models and then investigate the effect of model parameters on the observational display and space-time structure of BHs in the framework of our considering system. Under the incompatible configuration of the emission profiles, the images of BHs comprise that the observed luminosity is mainly determined by direct emission, while the lensing ring will provide a small contribution of the total observed flux and the photon ring makes a negligible contribution due to its exponential narrowness. More importantly, the observed regions and specific intensities of all emission profiles are changed correspondingly under variations of parameters. For optically thin accreting matters, we analyze the profile and specific intensity of the shadows with static and infalling accretions models, respectively. We find that with an infalling motion the interior region of the shadows will be darker than in a static case, due to the Doppler effect of the infalling movement. Finally, it is concluded that these findings support that the change of BH state parameters will change the way of space-time geometry, thus affecting the BH shadows dynamics.

gr-qc↗

arXiv2022

Effect of dark matter on shadows and rings of a brane-world black hole illuminated by various accretions

In this paper, by taking the accretions into account, the observational shadows and rings casted by the Brane-world black hole are numerically investigated when the observer located at the cosmological horizon. The results here show that the radius $r_p$ of photon sphere increased with cosmological parameter $α$ and dark matter parameter $β$, while the impact parameter $b_p$ decreased with $α$ and increased with $β$. For the thin-disk accretion, it turns out that the total observed intensity are mainly composed of the direct emission, while lensing ring and photon ring only contribute a small contribution and a negligible contribution, respectively. And, we find that shadow and rings exhibit some different and interesting features when the disk located at different positions. For the static and infalling spherical accretions, it is obvious that the size of shadow is always the same for both accretions, which means that shadow is only related to the geometry of space time in this case. The luminosity of shadow and photon sphere are closely related to the Doppler effect and the emissivity per unit volume $j({ν_e})$. In addition, the influence of dark matter and cosmological constant on observed intensity of shadows and rings are carefully emphasized throughout of this paper. Finally, we obtained the burring images of shadows and rings by using the nominal resolution of the Event Horizon Telescope, and studied the upper limits on the X-clod dark matter parameter $β$ with the aid of the data of the shadow of M87.

gr-qc↗

arXiv2022

The shadows and observational appearance of a noncommutative black hole surrounded by various profiles of accretions

The accretion around the black hole plays a pivotal role in the theoretical analysis of black hole shadow, and of the black hole observation in particular. In this paper, we mainly study the shadow and observation characteristics of noncommutative Schwarzschild black holes wrapped by three accretion models, and then explore the influence of noncommutative parameters on the observation appearance and spacetime geometry of black holes. When the black hole is surrounded by an optically and geometrically thin accretion disk, it shows that the direct emissions always dominate the total observed intensity, while the lensing ring superimposed upon the direct emission produces a thin ring, which improves the observation intensity of the black hole image. However, the photon rings makes a negligible contributions to the total observed brightness due to its exponential narrowness, although the photon ring intersects the thin plane more than three times to pick up larger intensity. More importantly, when the noncommutative parameters changed, the corresponding regions and observation intensities of photon ring, lensing ring and direct emission all change correspondingly. For optical thin spherically symmetric accretion, we consider the static and infalling matters, respectively. We find that the observation intensity of the two spherical accretion models increase with the increase of noncommutative parameters. In addition, due to the Doppler effect of the infalling movement, the shadow image of infalling accretion is darker than that of static accretion. In a word, the different accretion models and noncommutative parameters will lead to different shadow images and optical appearances of noncommutative Schwarzschild black holes.

hep-th↗

arXiv2021

Thermodynamics and weak cosmic censorship conjecture in Born-Infeld-anti-de Sitter black holes

We examine the laws of thermodynamics and the weak cosmic censorship conjecture in the normal and extended phase space of Born-Infeld-anti-de Sitter black hole by considering a charged particle absorption. In the normal phase space, the first and second law of thermodynamics as well as the weak cosmic censorship are still valid. However, in the extended phase space, the second law of thermodynamics is violated for double-horizon black holes and part of single-horizon black holes. The first law of thermodynamics and the weak cosmic censorship conjecture are still valid for all black holes. In addition, we find that the shift of the metric function, which determines the locations of the horizons, takes the same form at the minimum point in both the normal and extended phase space, indicating that the weak cosmic censorship conjecture is independent of the thermodynamic phase space.

hep-th↗

arXiv2020

Thermodynamics and weak cosmic censorship conjecture in the Kerr-AdS black hole

We investigate the laws of thermodynamics and weak cosmic censorship conjecture in the normal and extended phase space of a Kerr-AdS black hole by analyzing the energy-momentum relation of the absorbed fermion dropping into the horizon. In the normal phase space, the first law, second law as well as the weak cosmic censorship conjecture are found to be valid in all the initial states of the black hole. However, in the extended phase space, although the first law and weak cosmic censorship conjecture are still valid, the second law becomes more subtle. We find that the validity or violation of the second law depends on the spin parameter, the radius of the AdS spacetime, and their variations. In addition, in the extended phase space, the configurations of the extremal and near-extremal Kerr-AdS black holes are unchanged as the fermions are absorbed since the final and initial states are the same.

gr-qc↗

arXiv2020

Shadows and photon spheres with spherical accretions in the four-dimensional Gauss-Bonnet black hole

We investigate the shadows and photon spheres of the four-dimensional Gauss-Bonnet black hole with the static and infalling spherical accretions. We show that for both cases, the shadow and photon sphere are always present. The radii of the shadow and photon sphere are independent of the profiles of accretion for a fixed Gauss-Bonnet constant, implying that the shadow is a signature of the spacetime geometry and it is hardly influenced by accretion in this case. Because of the Doppler effect, the shadow of the infalling accretion is found to be darker than that of the static one. We also investigate the effect of the Gauss-Bonnet constant on the shadow and photon sphere, and find that the larger the Gauss-Bonnet constant is, the smaller the radii of the shadow and photon sphere will be. In particular, the observed specific intensity increases with the increasing of the Gauss-Bonnet constant.

gr-qc↗

arXiv2020

Influence of quintessence dark energy on the shadow of black hole

We investigate the effects of quintessence dark energy on the shadows of black hole, surrounded by various profiles of accretions. For the thin disk accretion, the images of the black hole comprises the dark region and bright region, including direct emission, lensing rings and photon rings. Although their details depend on the form of the emission, generically, the direct emission plays a major role for the observed brightness of the black hole, while the lensing ring makes a small contribution and photon ring makes a negligible contribution. The existence of cosmological horizon also plays an important role in the shadows, since the observer in the domain of outer communications is nearby the cosmological horizon. For the spherically symmetric accretion, the static and infalling matters are considered. We find that the positions of photon spheres are the same for both static and infalling accretions. However, the observed specific intensity of the image for the infalling accretion is darker than the static accretion, due to the Doppler effect of the infalling movement.

gr-qc↗

arXiv2020

Thermodynamics and weak cosmic censorship conjecture of an AdS black hole with a monopole in the extended phase space

The first law of black hole thermodynamics in the extended phase space is prevailing recently. However, the second law as well as the weak cosmic censorship conjecture has not been investigated extensively. In this paper, we investigate the laws of thermodynamics and the weak cosmic censorship conjecture of an AdS black hole with a global monopole in the extended phase space under a charged particle absorption. It is shown that the first law of thermodynamics is valid, while the second law is violated for the extremal and near-extremal black holes. Moreover, we find the weak cosmic censorship conjecture is valid only for the extremal black hole, but is violable for the near-extremal black hole. It is different from the previous results where the high order corrections were neglected.

gr-qc↗

arXiv2019

Thermodynamics and weak cosmic censorship conjecture of the BTZ black holes in the extended phase space

As charged fermions drop into the BTZ black holes, we check the laws of thermodynamics and weak cosmic censorship conjecture in the normal phase space and extended phase space, where the cosmological parameter and renormalization length are regarded as extensive quantities. In the normal phase space, the first and second law of thermodynamics as well as the weak cosmic censorship are valid. While in the extended phase space, though the first law and weakcosmic censorship conjecture are still valid, the second law is dependent on the variation of the renormalization energy $dK$. In addition, in the extended phase space, the configurations of the extremal and near-extremal black holes will not be changed for they are stable while in the normal phase space, the extremal and near-extremal black holes will evolve into non-extremal black holes.

gr-qc↗

arXiv2019

The weak cosmic censorship conjecture and thermodynamics in the quintessence AdS black hole under charge particle absorption

Considering the cosmological constant as the pressure, we mainly study the laws of thermodynamics and weak cosmic censorship conjecture in the Reissner-Nordström-AdS black hole surrounded by quintessence dark energy under charged particle absorption. The first law of thermodynamics is found to be valid as a particle is absorbed by the black hole. The second law however is found to be violated for the extremal and near-extremal black holes since the entropy of these black hole decrease. Moreover, we find that the extremal black hole do not change it configuration in the extended phase space, implying that the weak cosmic censorship conjecture is valid. Remarkably, the near-extremal black hole can be overcharged beyond the extremal condition under charged particle absorption. That is, the cosmic censorship conjecture could be violated for the near-extremal black hole in the extended phase space. To make a comparison, we also discuss the first law, second law as well as the weak cosmic censorship conjecture in the normal phase space, and find that all of them are valid in this case.

gr-qc↗

arXiv2019

Weak cosmic censorship conjecture with pressure and volume in the Gauss-Bonnet AdS black hole

With the Hamilton-Jacobi equation, we obtain the energy-momentum relation of a charged particle as it is absorbed by the Gauss-Bonnet AdS black hole. On the basis of the energy-momentum relation at the event horizon, we investigate the first law, second law, and weak cosmic censorship conjecture in both the normal phase space and extended phase space. Our results show that the first law, second law as well as the weak cosmic censorship conjecture are valid in the normal phase space for all the initial states are black holes. However, in the extended phase space, the second law is violated for the extremal and near-extremal black holes, and the weak cosmic censorship conjecture is violable for the near-extremal black hole, though the first law is still valid. In addition, in both the the normal and extended phase spaces, we find the absorbed particle changes the configuration of the near-extremal black hole, while don't change that of the extremal black hole.

hep-th↗

arXiv2019

Thermodynamics and weak cosmic censorship conjecture with pressure in the rotating BTZ black holes

As a charged spinning fermion drops into a charged rotating BTZ black hole, we investigate the laws of thermodynamics and weak cosmic censorship conjecture with and without pressure respectively. For the case without pressure, the first law, second law, as well as the weak cosmic censorship are found to be valid. While for the case with pressure, though the first law is still valid, the second law and the weak cosmic censorship conjecture are found to be violable, depending on the charge, angular momentum, AdS radius, and their variations. In addition, in both cases, the configurations of the extremal black holes are found to be stable since the final states of the extremal black holes are still extremal black holes. While for the near-extremal black holes, their configurations are not stable.

gr-qc↗

arXiv2019

Thermodynamics and weak cosmic censorship conjecture of the torus-like black hole

After studying the energy-momentum relation of charged particles' Hamilton-Jacobi equations, we discuss the laws of thermodynamics and the weak cosmic censorship conjecture in torus-like black holes. We find that both the first law of thermodynamic as well as the weak cosmic censorship conjecture are valid in both the normal phase space and extended phase space. However, the second law of thermodynamics is only valid in the normal phase space. Our results show that the first law and weak cosmic censorship conjecture do not depend on the phase spaces while the second law depends. What's more, we find that the shift of the metric function that determines the event horizon take the same form in different phase spaces, indicating that the weak cosmic censorship conjecture is independent of the phase space.

hep-th↗

arXiv2019

Thermodynamics and weak cosmic censorship conjecture in (2+1)-dimensional regular black hole with nonlinear electrodynamics sources

We study the dynamical behavior of spinor particles, and get the energy-momentum relation of charged particles by solving the Dirac equation. Based on the energy-momentum relation, we investigate the laws of thermodynamics and the weak cosmic censorship conjecture for the (2+1)-dimensional regular black hole with nonlinear electrodynamics sources in the normal phase space and the extended phase space. Our results show that the first law of thermodynamics as well as the weak cosmic censorship conjecture are valid in both the phase spaces. However, the second law of thermodynamics is violated in the extended phase space, implying that the first law and weak cosmic censorship conjecture do not depend on the phase space while the second law depends. In addition, in the extended phase space, we find the configurations of the extremal and near-extremal black holes will not be changed for the final states and initial states are the same.

gr-qc↗