arXiv subjects

Yan-Gang Miao

Publications and source records attributed to Yan-Gang Miao.

At least 55 records · Page 3Linked to original sources

arXiv2021

Quasinormal modes and shadows of a new family of Ayón-Beato-Garc\'ıa black holes

We obtain a type of Ayón-Beato-Garc\'ıa (ABG) related black hole solutions with five parameters: the mass $m$, the charge $q$, and three dimensionless parameters $α$, $β$ and $γ$ associated with nonlinear electrodynamics. We find that this type of black holes is regular under the conditions: $αγ\geqslant 6$, $βγ\geqslant 8$, and $γ>0$. Here we focus on the saturated case: $α={6}/γ$ and $β={8}/{γ}$, such that only three parameters $m$, $q$ and $γ$ remain, which leads to a new family of ABG black holes. For such a family of black holes, we investigate the influence of the charge $q$ and the parameter $γ$ on the horizon radius and the Hawking temperature. In addition, we calculate the quasinormal mode frequencies of massless scalar field perturbations by using the sixth-order WKB approximation method and the unstable circular null geodesic method in the eikonal limit. We also compute the shadow radius for the new family of ABG black holes and use the shadow data of the $M87^{*}$ black hole detected by the Event Horizon Telescope to provide an upper limit on the charge $q$ of the new black holes. Using the shadow data of the $M87^{*}$ black hole, we find that the upper limit of the charge $q$ increases rapidly at first and then slowly but does not exceed the mass of the $M87^{*}$ black hole at last when the parameter $γ$ is increasing and going to infinity, and that the data restrict the frequency range of the fundamental mode with $l=1$ to $1.4\times 10^{-6}Hz\sim 1.9\times 10^{-6} Hz$.

gr-qc↗

arXiv2021

Entropy and Topology of Regular Black Holes

We calculate the entropy of spherically symmetric regular black holes by the path integral and Noether-charge method. Both methods provide an evidence that the entropy of regular black holes should be proportional to quarter of area, and there is no violation of entropy/area law at all.

gr-qc↗

arXiv2021

Connections between entropy surface density and microscopic property in black holes

We introduce a new microscopic quantity $\varepsilon $ that describes the contribution of a single black hole molecule to black hole entropy and give a key relation that this microscopic quantity is proportional to the macroscopic quantity -- entropy surface density $σ_{S}$, thus connecting a microscopic quantity to a macroscopic quantity of black holes. Such a connection provides a new probe for understanding the black hole microstructure from the macroscopic perspective. We also classify black holes in terms of entropy surface density. When its entropy surface density is larger (smaller) than $1/4$, this type of black holes is defined as strong (weak) Bekenstein-Hawking black holes, where the black holes with $1/4$-entropy surface density are regarded as Bekenstein-Hawking black holes. We compute the entropy surface density for four models, where three of them are regular black holes -- the Bardeen black hole, the Ayón-Beato-Garc\'ıa black hole, and the Hayward black hole, and one of them is a singular black hole -- the five-dimensional neutral Gauss-Bonnet black hole. Under this scheme of classification, the Bardeen black hole, the Ayón-Beato-Garc\'ıa black hole, and the five-dimensional neutral Gauss-Bonnet black hole belong to the type of strong Bekenstein-Hawking black holes, but the Hayward black hole belongs to the type of weak Bekenstein-Hawking black holes, and the four black holes approach to the Bekenstein-Hawking black hole if their event horizon radii go to infinity. In addition, we find interesting properties in phase transitions from the viewpoint of entropy surface density, or equivalently from the viewpoint of a single black hole molecule entropy, for the five-dimensional neutral Gauss-Bonnet AdS black hole.

gr-qc↗

arXiv2021

Can shadows connect black hole microstructures?

We investigate the relationship between shadow radii (photosphere radii) and black hole microstructures for a static spherically symmetric black hole and confirm their close connection. As a concrete analysis, we take the Reissner-Nordstr$\mathrm{\ddot{o}}$m AdS black hole surrounded by perfect fluid dark matter (RN AdS black hole surrounded by PFDM) as an example. We calculate the Ruppeiner thermodynamic scalar curvature and shadow radius (photosphere radius) for the specific model. On the one hand, we find that the greater density of the perfect fluid dark matter makes black hole molecules more likely have attractive interactions. On the other hand, we provide the support to our general investigation that the shadow radii (photosphere radii) indeed connect the microstructures of this model.

gr-qc↗

arXiv2020

Null geodesics, quasinormal modes and the correspondence with shadows in high-dimensional Einstein-Yang-Mills spacetimes

Null geodesics, quasinormal modes of a massless scalar field perturbation and the correspondence with shadow radii are investigated in the background spacetime of high-dimensional Einstein-Yang-Mills black holes. Based on the properties of null geodesics, we obtain the connection between the radius of a photon sphere and the radius of a horizon in the five- and six-dimensional Einstein-Yang-Mills spacetimes. Especially in the five-dimensional case, there exist two branches for the radius of a photon sphere, but only the branch outside the event horizon satisfies the condition of circular null geodesics. Moreover, we find no reflecting points of shadow radii and no spiral-like shapes on the complex plane of quasinormal frequencies and verify the correspondence between the quasinormal modes in the eikonal limit and shadow radii in high-dimensional Einstein-Yang-Mills spacetimes.

hep-th↗

arXiv2020

Quasinormal Modes of the Generalized Ayón-Beato-Garc\'ıa Scalar-Tensor-Vector Gravity Black Hole in the Scalar-Tensor-Vector Gravity

We obtain the solution of a generalized ABG STVG black hole with the nonlinear tensor field $B_{μν}$ in the scalar-tensor-vector gravity. This black hole is endowed with four parameters, the black hole mass $M$, the parameter $α$ associated with the STVG theory, and the two parameters $λ$ and $β$ that are related to the dipole and quadrupole moments of the nonlinear tensor field, respectively. By analyzing the characteristics of the black hole, we find that the generalized ABG STVG black hole is regular when $λ\geqslant 3$ and $β\geqslant 4$, and we study the effects of the parameters $α$, $λ$ and $β$ on the black hole horizon. We calculate the quasinormal mode frequencies of the odd parity gravitational perturbation for the generalized ABG STVG black hole by using the 6th order WKB approximation method and simultaneously by the null geodesic method at the eikonal limit. The results show that the increase of the parameters $α$ and $λ$ makes the gravitational waves decay slowly, while the increase of the parameter $β$ makes the gravitational waves decay fast at first and then slowly. In addition, we verify that the improved correspondence between the real part of quasinormal frequencies at the eikonal limit and the shadow radius is valid for the generalized ABG STVG black hole.

gr-qc↗

arXiv2020

Scalar quasinormal modes of black holes in Einstein-Yang-Mills gravity

Quasinormal modes of a scalar field perturbation are investigated in the background spacetime of Einstein-Yang-Mills black holes. The logarithmic term in the metric function of the five-dimensional Einstein-Yang-Mills black hole eliminates the divergence of the Hawking temperature but maintains the charge-dependent behavior of the quasinormal modes. The real and imaginary parts of quasinormal mode frequencies have the same charge-dependent behavior in different dimensions. Similar to the case of high dimensional Schwarzschild black holes, a compact approximate relation, $ω_{\rm R}\sim D/r_{+}$, also exists between the real part of the quasinormal mode frequencies $ω_{\rm R}$ and the number of dimensions $D$ in the higher than five dimensional Einstein-Yang-Mills black holes.

hep-th↗

arXiv2020

Quasinormal mode and spectroscopy of a Schwarzschild black hole surrounded by a cloud of strings in Rastall gravity

We obtain the solution of a static spherically symmetric black hole surrounded by a cloud of strings in Rastall gravity and study the influence of the parameter $a$ associated with strings on the event horizon and the Hawking temperature. Through analyzing the black hole metric, we find that the static spherically symmetric black hole solution surrounded by a cloud of strings in Rastall gravity can be transformed into the static spherically symmetric black hole solution surrounded by quintessence in Einstein gravity when the parameter $β$ of Rastall gravity is positive, which provides a possibility for the string fluid to be a candidate of dark energy. We use the method of Regge and Wheeler together with the high order WKB-Padé approximation to calculate the quasinormal mode frequencies of the odd parity gravitational perturbation and simultaneously apply the unstable null geodesics of black holes to compute the quasinormal mode frequencies at the eikonal limit for this black hole model. The results show that the increase of the parameter $a$ makes the gravitational wave decay slowly in Rastall gravity. In addition, we utilize two methods, which are based on the adiabatic invariant integral and the periodic property of outgoing waves, respectively, to derive the area spectrum and entropy spectrum of the black hole model. The results show that the area spectrum and entropy spectrum are equidistant spaced. The former is same as the case of Einstein gravity, while the latter is different, depending on the Rastall parameter $β$.

hep-th↗

arXiv2020

Quasinormal mode and stability of optical black holes in moving dielectrics

We study the quasinormal mode and stability of optical black holes in moving dielectrics. The results show that the real part of complex frequencies is inversely proportional to but the absolute value of an imaginary part is proportional to a refractive index. We obtain the conditions for forming a black hole horizon in moving dielectrics. Moreover, we investigate the evolution behavior of optical black holes with respect to a refractive index at a high overtone number and find that an optical black hole undergoes one phase transition from an unstable mode to a stable one when the refractive index is big enough.

gr-qc↗

arXiv2019

Microscopic structures and thermal stability of black holes conformally coupled to scalar fields in five dimensions

Completely from the thermodynamic point of view, we explore the microscopic character of a hairy black hole of Einstein's theory conformally coupled to a scalar field in five dimensions by means of the Ruppeiner thermodynamic geometry. We demonstrate that the scalar hairy black hole has rich microscopic structures in different parameter spaces. Moreover, we analyze the thermal stability of this black hole in detail.

hep-th↗

arXiv2018

Parametric phase transition for Gauss-Bonnet AdS black hole

With the help of the parametric solution of the Maxwell equal area law for the Gauss-Bonnet AdS black hole in five dimensions, we find the second analytical solution to the first order phase transition. We analyze the asymptotic behaviors of some characteristic thermodynamic properties for the small and large black holes at the critical and zero temperatures and also calculate the critical exponents and the corresponding critical amplitudes in detail. Moreover, we give the general form of the thermodynamic scalar curvature based on the Ruppeiner geometry and point out that the attractive interaction dominates in both the small and large black hole phases when the first order phase transition occurs in the five dimensional Gauss-Bonnet AdS black hole.

hep-th↗

arXiv2018

On thermal molecular potential among micromolecules in charged AdS black holes

Considering the unexpected similarity between the thermodynamic features of charged AdS black holes and that of the van der Waals fluid system, we calculate the number densities of black hole micromolecules and derive the thermodynamic scalar curvature for the small and large black holes on the co-existence curve based on the so-called Ruppeiner thermodynamic geometry. We reveal that the microscopic feature of the small black hole perfectly matches that of the ideal anyon gas, and that the microscopic feature of the large black hole matches that of the ideal Bose gas. More importantly, we investigate the issue of molecular potential among micromolecules of charged AdS black holes, and point out explicitly that the well-known experiential Lennard-Jones potential is a feasible candidate to describe interactions among black hole micromolecules completely from a thermodynamic point of view. The behavior of the interaction force induced by the Lennard-Jones potential coincides with that of the thermodynamic scalar curvature. Both the Lennard-Jones potential and the thermodynamic scalar curvature offer a clear and reliable picture of microscopic structures for the small and large black holes on the co-existence curve for charged AdS black holes.

hep-th↗

arXiv2018

Interaction potential and thermo-correction to the equation of state for thermally stable Schwarzschild Anti-de Sitter black holes

The microscopic structure of black holes remains a challenging subject. In this paper, based on the well-accepted fact that black holes can be mapped to thermodynamic systems, we make a preliminary exploration of the microscopic structure of the thermodynamically stable Schwarzschild anti-de-Sitter (SAdS) black hole. In accordance with the number density and thermodynamic scalar curvature, we give the interaction potential among the molecules of thermodynamically stable SAdS black holes and analyze its effectiveness. Moreover, we derive the thermo-correction to the equation of state for such black holes that arises from interactions among black-hole molecules using virial coefficients.

hep-th↗

arXiv2017

Complexity/Action duality of shock wave geometry in a massive gravity theory

On the holographic complexity dual to the bulk action, we investigate the action growth for a shock wave geometry in a massive gravity theory within the Wheeler-De Witt (WDW) patch at the late time limit. For a global shock wave, the graviton mass does not affect the action growth in the bulk, i.e. the complexity on the boundary, showing that the action growth (complexity) is the same for both the Einstein gravity and the massive gravity. Nevertheless, for a local shock wave that depends on transverse coordinates, the action growth (complexity) is proportional to the butterfly velocity for the two gravity theories, but the butterfly velocity of the massive gravity theory is smaller than that of the Einstein gravity theory, indicating that the action growth (complexity) of the massive gravity is depressed by the graviton mass. In addition, we extend the black hole thermodynamics of the massive gravity and obtain the right Smarr formula.

hep-th↗

arXiv2017

Hawking Radiation of Five-dimensional Charged Black Holes with Scalar Fields

We investigate the Hawking radiation cascade from the five-dimensional charged black hole with a scalar field coupled to higher-order Euler densities in a conformally invariant manner. We give the semi-analytic calculation of greybody factors for the Hawking radiation. Our analysis shows that the Hawking radiation cascade from this five-dimensional black hole is extremely sparse. The charge enhances the sparsity of the Hawking radiation, while the conformally coupled scalar field reduces this sparsity.

hep-th↗

arXiv2017

Validity of Maxwell Equal Area Law for Black Holes Conformally Coupled to Scalar Fields in $\text{AdS}_5$ Spacetime

We investigate the $P-V$ criticality and the Maxwell equal area law for a five-dimensional spherically symmetric AdS black hole with a scalar hair in the absence of and in the presence of a Maxwell field, respectively. Especially in the charged case, we give the exact $P-V$ critical values. More importantly, we analyze the validity and invalidity of the Maxwell equal area law for the AdS hairy black hole in the scenarios without and with charges, respectively. Within the scope of validity of the Maxwell equal area law, we point out that there exists a representative van der Waals-type oscillation in the $P-V$ diagram. This oscillating part that indicates the phase transition from a small black hole to a large one can be replaced by an isobar. The small and large black holes share the same Gibbs free energy. We also give the distribution of the critical points in the parameter space both without and with charges, and obtain for the uncharged case the fitting formula of the co-existence curve. Meanwhile, the latent heat is calculated, which gives the energy released or absorbed between the small and large black hole phases in the isothermal-isobaric procedure.

hep-th↗

arXiv2017

Phase transition and entropy inequality of noncommutative black holes in a new extended phase space

We analyze the thermodynamics of the noncommutative high-dimensional Schwarzschild-Tangherlini AdS black hole with the non-Gaussian smeared matter distribution by regarding a noncommutative parameter as an independent thermodynamic variable named as the noncommutative pressure. In the new extended phase space that includes this noncommutative pressure and its conjugate variable, we reveal that the noncommutative pressure and the original thermodynamic pressure related to the negative cosmological constant make the opposite effects in the phase transition of the noncommutative black hole, i.e. the former dominates the UV regime while the latter does the IR regime, respectively. In addition, by means of the reverse isoperimetric inequality, we indicate that only the black hole with the Gaussian smeared matter distribution holds the maximum entropy for a given thermodynamic volume among the noncommutative black holes with various matter distributions.

hep-th↗

arXiv2016

Thermodynamics of the Schwarzschild-AdS black hole with a minimal length

Using the mass-smeared scheme of black holes, we study the thermodynamics of black holes. Two interesting models are considered. One is the self-regular Schwarzschild-AdS black hole whose mass density is given by the analogue to probability densities of quantum hydrogen atoms. The other model is the same black hole but whose mass density is chosen to be a rational fractional function of radial coordinates. Both mass densities are in fact analytic expressions of the $δ$-function. We analyze the phase structures of the two models by investigating the heat capacity at constant pressure and the Gibbs free energy in an isothermal-isobaric ensemble. Both models fail to decay into the pure thermal radiation even with the positive Gibbs free energy due to the existence of a minimal length. Furthermore, we extend our analysis to a general mass-smeared form that is also associated with the $δ$-function, and indicate the similar thermodynamic properties for various possible mass-smeared forms based on the $δ$-function.

hep-th↗