Joule-Thomson expansion of the regular(Bardeen)-AdS black hole

We study the Joule-Thomson expansion of the regular black hole in an anti-de Sitter background,and obtain the inversion temperature for the Bardeen-AdS black hole in the extended phase space.We investigate the isenthalpic and inversion curves for the Bardeen-AdS black hole in the T-P plane and find that the intersection points between them are exactly the inversion points discriminating the heating from the cooling process.The inversion curve for the regular(Bardeen)-AdS black hole is not closed and there is only a lower inversion curve,in contrast to the Van der Waals fluid.Most importantly,we find that the ratio between the minimum inversion temperature and the critical temperature for the regular(Bardeen)-AdS black hole is 0.536622,which is larger than any known ratio for the singular black hole.The large ratio for the Bardeen-AdS black hole may be due to the repulsive de Sitter core near the origin of the regular black hole.     

Bardeen black hole surrounded by perfect fluid dark matter

We derive an exact solution for a spherically symmetric Bardeen black hole surrounded by perfect fluid dark matter (PFDM). By treating the magnetic charge g and dark matter parameter \begin{document}$\alpha$\end{document} as thermodynamic variables, we find that the first law of thermodynamics and the corresponding Smarr formula are satisfied. The thermodynamic stability of the black hole is also studied. The results show that there exists a critical radius \begin{document}$r_{+}^{C}$\end{document} where the heat capacity diverges, suggesting that the black hole is thermodynamically stable in the range \begin{document}$0<r_{+}<r_{+}^{C}$\end{document} . In addition, the critical radius \begin{document}$r_{+}^{C}$\end{document} increases with the magnetic charge g and decreases with the dark matter parameter \begin{document}$\alpha$\end{document} . Applying the Newman-Janis algorithm, we generalize the spherically symmetric solution to the corresponding rotating black hole. With the metric at hand, the horizons and ergospheres are studied. It turns out that for a fixed dark matter parameter \begin{document}$\alpha$\end{document} , in a certain range, with the increase of the rotation parameter a and magnetic charge g, the Cauchy horizon radius increases while the event horizon radius decreases. Finally, we investigate the energy extraction by the Penrose process in a rotating Bardeen black hole surrounded by PFDM.     

Fermion tunnels of higher-dimensional anti-de Sitter Schwarzschild black hole and its corrected entropy

Applying the method beyond semiclassical approximation, fermion tunneling from higher-dimensional anti-de Sitter Schwarzschild black hole is researched. In our work, the “tortoise” coordinate transformation is introduced to simplify Dirac equation, so that the equation proves that only the (r−t) sector is important to our research. Because we only need to study the (r−t) sector, the Dirac equation is decomposed into several pairs of equations spontaneously, and we then prove the components of wave functions are proportional to each other in every pair of equations. Therefore, the suitable action forms of the wave functions are obtained, and finally the correctional Hawking temperature and entropy can be determined via the method beyond semiclassical approximation.     

Thermodynamics of regular black hole

We investigate thermodynamics for a magnetically charged regular black hole (MCRBH), which comes from the action of general relativity and nonlinear electromagnetics, comparing with the Reissner–Norström (RN) black hole in both four and two dimensions after dimensional reduction. We find that there is no thermodynamic difference between the regular and RN black holes for a fixed charge Q in both dimensions. This means that the condition for either singularity or regularity at the origin of coordinate does not affect the thermodynamics of black hole. Furthermore, we describe the near-horizon AdS₂ thermodynamics of the MCRBH with the connection of the Jackiw–Teitelboim theory. We also identify the near-horizon entropy as the statistical entropy by using the AdS₂/CFT₁ correspondence.     

Horizon structure of rotating Bardeen black hole and particle acceleration

We investigate the horizon structure and ergosphere in a rotating Bardeen regular black hole, which has an additional parameter (g) due to the magnetic charge, apart from the mass (M) and the rotation parameter (a). Interestingly, for each value of the parameter g, there exists a critical rotation parameter (\(a=a_{E}\)), which corresponds to an extremal black hole with degenerate horizons, while for \(a<a_{E}\) it describes a non-extremal black hole with two horizons, and no black hole for \(a>a_{E}\). We find that the extremal value \(a_E\) is also influenced by the parameter g, and so is the ergosphere. While the value of \(a_E\) remarkably decreases when compared with the Kerr black hole, the ergosphere becomes thicker with the increase in g. We also study the collision of two equal mass particles near the horizon of this black hole, and explicitly show the effect of the parameter g. The center-of-mass energy (\(E_\mathrm{CM}\)) not only depend on the rotation parameter a, but also on the parameter g. It is demonstrated that the \(E_\mathrm{CM}\) could be arbitrarily high in the extremal cases when one of the colliding particles has a critical angular momentum, thereby suggesting that the rotating Bardeen regular black hole can act as a particle accelerator.     

正则黑洞熵

应用隧道效应所得到的能量谱计算配分函数,进而计算黑洞熵.当本结论取一级近似时,熵修正的对数项与考虑广义不确定关系对黑洞熵修正的对数项一致,然而在计算中没有不确定因子.虽然对数修正项前的因子与考虑热波动对黑洞熵修正中对数项前的因子相同,但所给结论中当黑洞的热容量为负时也不存在发散项.所以本结论具有普遍性. 关键词： 广义不确定关系 热波动 正则系综 量子修正     

Schwarzschild-de Sitter黑洞宇宙视界量子态的熵

采用由广义不确定关系得到的新的态密度方程 ,研究了Schwarzchild deSitter时空背景下黑洞宇宙视界的熵 .利用新的态密度方程 ,克服了用brick wall模型方法计算黑洞熵 ,在消除紫外发散需取截断的不完善之处 ,以此揭示了黑洞熵与其视界面积成正比这一内在联系 ,进一步表明黑洞熵是视界面处量子态的熵     

Schwarzschild-de-Sitter黑洞宇宙视界量子态的熵

采用由广义不确定关系得到的新的态密度方程，研究了Schwarzchild-de-Sitter时空背景下黑洞宇宙视界的熵.利用新的态密度方程，克服了用brick wall模型方法计算黑洞熵，在消除紫外发散需取截断的不完善之处，以此揭示了黑洞熵与其视界面积成正比这一内在联系，进一步表明黑洞熵是视界面处量子态的熵. 关键词： 黑洞 广义不确定关系 态密度 熵     

Four-parametric regular black hole solution

We present a regular class of exact black hole solutions of the Einstein equations coupled with a nonlinear electrodynamics source. For weak fields the nonlinear electrodynamics becomes the Maxwell theory, and asymptotically the solutions behave as the Reissner–Nordström one. The class is endowed with four parameters, which can be thought of as the mass m, charge q, and a sort of dipole and quadrupole moments and , respectively. For 3, 4, and |q|2s _c m the corresponding solutions are regular charged black holes. For = 3, they also satisfy the weak energy condition. For = = 0 we recover the Reissner–Nordström singular solution and for = 3, = 4 the family includes a previous regular black hole reported by the authors.     

Two dimensional black hole entropy

In this paper we consider the two dimensional black hole and use Wald’s formula to find its entropy. Also we consider higher derivative terms. We discuss the case of a massless black hole and find its free energy.     

Universal canonical black hole entropy

Nonrotating black holes in three and four dimensions are shown to possess a canonical entropy obeying the Bekenstein-Hawking area law together with a leading correction (for large horizon areas) given by the logarithm of the area with a universal finite negative coefficient, provided one assumes that the quantum black hole mass spectrum has a power-law relation with the quantum area spectrum found in nonperturbative canonical quantum general relativity. The thermal instability associated with asymptotically flat black holes appears in the appropriate domain for the index characterizing this power-law relation, where the canonical entropy (free energy) is seen to turn complex.     

黑洞的统计熵

运用量子统计的方法,直接求解Schwarzschild时空背景下玻色场和费米场的配分函数,得到熵的积分表达式.按照最近的研究结果,认为黑洞的Hawking辐射过程是隧道效应过程,在考虑黑洞隧道效应产生过程中黑洞能量发生变化的基础上,给出积分的下限为黑洞的视界位置.由此得到黑洞熵的主要项为视界面积的1/4.不存在使人疑惑的紫外截断因子,并且由此可得黑洞辐射粒子的能量与辐射温度成正比的结论. 关键词： 黑洞熵 量子统计 隧道效应 反作用     

Kerr-Newman黑洞的统计熵

避开求解黑洞背景下波动方程的困难,应用量子统计方法,直接求解轴对称KerrNewman黑洞背景下Bose场和Fermi场的配分函数.然后利用改进的brickwall方法膜模型,计算黑洞背景下Bose场和Fermi场的熵.得到黑洞熵与视界面积成正比的结论.在所得结论中不存在对数发散项与舍去项,也不存在黑洞视界外标量场或Dirac场为什么是黑洞熵疑难,并且给出粒子的自旋简并度对黑洞熵的影响.为研究各种复杂黑洞熵提供了简捷的途径. 关键词： 量子统计 brick-wall方法 膜模型 黑洞熵     

Quantum aspects of black hole entropy

This survey intends to cover recent approaches to black hole entropy which attempt to go beyond the standard semiclassical perspective. Quantum corrections to the semiclassical Bekenstein-Hawking area law for black hole entropy, obtained within the quantum geometry framework, are treated in some detail. Their ramification for the holographic entropy bound for bounded stationary spacetimes is discussed. Four dimensional supersymmetric extremal black holes in string-based N=2 supergravity are also discussed, albeit more briefly.     

Barriola-Vilenkin黑洞的统计熵

利用量子统计方法 ,直接计算Barriola_Vilenkin黑洞背景下玻色场和费米场的配分函数 ,然后利用砖墙膜模型计算和讨论黑洞背景下玻色场和费米场的熵     

Barriola-Viienkin黑洞的统计熵

利用量子统计方法,直接计算Barriola-Vilenkin黑洞背景下玻色场和费米场的配分函数,然后利用砖墙膜模型计算和讨论黑洞背景下玻色场和费米场的熵.     

Tachyon condensation and black hole entropy

String propagation on a cone with deficit angle 2pi(1-1 / N) is considered for the purpose of computing the entropy of a large mass black hole. The entropy computed using the recent results on condensation of twisted-sector tachyons in this theory is found to be in precise agreement with the Bekenstein-Hawking entropy.