Energy and Momentum of Higher Dimensional Black Holes

In this paper, we devote to investigate the energy-momentum problem of higher dimensional black holes in the general theory of relativity. The energy and momentum complex of M?ller has been used for the calculations. Also, total energy and total momentum of some special cases for higher dimensional black holes such as Schwarzschild-like black holes, Reissner-Nordstr?m-like charged black holes, AdS-like black holes, topological black holes, BTZ-like and charged BTZ-like black holes were obtained. It is invented that the momentum of black holes vanishes everywhere while the energy of black holes are not equal to zero in higher dimension. Also the results agree with Yang and Radinschi or Vagenas results in three and four dimensional black holes, respectively (Jang and Radinschi in AIP Conf. Proc. 895, 325, 2007; Vagenas in Mod. Phys. Lett. A 21, 1947, 2006).     

Rotating black holes in dilatonic Einstein-Gauss-Bonnet theory

We construct generalizations of the Kerr black holes by including higher-curvature corrections in the form of the Gauss-Bonnet density coupled to the dilaton. We show that the domain of existence of these Einstein-Gauss-Bonnet-dilaton (EGBD) black holes is bounded by the Kerr black holes, the critical EGBD black holes, and the singular extremal EGBD solutions. The angular momentum of the EGBD black holes can exceed the Kerr bound. The EGBD black holes satisfy a generalized Smarr relation. We also compare their innermost stable circular orbits with those of the Kerr black holes and show the existence of differences which might be observable in astrophysical systems.     

Accretion,primordial black holes and standard cosmology

Primordial black holes evaporate due to Hawking radiation. We find that the evaporation times of primordial black holes increase when accretion of radiation is included. Thus, depending on accretion efficiency, more primordial black holes are existing today, which strengthens the conjecture that the primordial black holes are the proper candidates for dark matter.     

Can black holes be torn up by phantom dark energy in cyclic cosmology?

Infinitely cyclic cosmology is often frustrated by the black hole problem. It has been speculated that this obstacle in cyclic cosmology can be removed by taking into account a peculiar cyclic model derived from loop quantum cosmology or the braneworld scenario, in which phantom dark energy plays a crucial role. In this peculiar cyclic model, the mechanism of solving the black hole problem is through tearing up black holes by phantom. However, using the theory of fluid accretion onto black holes, we show in this paper that there exists another possibility: that black holes cannot be torn up by phantom in this cyclic model. We discussed this possibility and showed that the masses of black holes might first decrease and then increase, through phantom accretion onto black holes in the expanding stage of the cyclic universe.     

Thermodynamics of Third Order Lovelock Anti-de Sitter Black Holes Revisited

We compute the mass and temperature of third order Lovelock black holes with negative Gauss-Bonnet coefficient α₂<0 in anti-de Sitter space and perform the stability analysis of topological black holes. When k=-1, the third order Lovelock black holes are thermodynamically stable for the whole range r₊. When k=1, we found that the black hole has an intermediate unstable phase for D=7. In eight dimensional spacetimes, however, a new phase of thermodynamically unstable small black holes appears if the coefficient \tilde{\alpha} is under a critical value.For D≧ 9, black holes have similar the distributions of thermodynamically stable regions to the case where the coefficient \tilde{\alpha} is under a critical value for D=8. It is worth to mention that all the thermodynamic and conserved quantities of the black holes with flat horizon do not depend on the Lovelock coefficients and are the same as those of black holes in general gravity.     

Entropy spectrum of the D-dimensional massless topological black hole

There are exact solutions to Einstein’s equations with negative cosmological constant that represent black holes whose event horizons are manifolds of negative curvature, the so-called topological black holes. Among these solutions there is one, the massless topological black hole, whose mass is equal to zero. Hod proposes that in the semiclassical limit the asymptotic quasinormal frequencies determine the entropy spectrum of the black holes. Taking into account this proposal, we calculate the entropy spectrum of the massless topological black hole and we compare with the results on the entropy spectra of other topological black holes.     

Weighing black holes in the universe

The determination of the mass of black holes in our universe is crucial to understand their physics nature but is a great challenge to scientists. In this paper I briefly review some methods that are currently used to estimate the mass of black holes, especially those in X-ray binary systems and in galactic nuclei. Our recent progress in improving the mass estimates of supermassive black holes in active galactic nuclei by involving some empirical relations is presented. Finally I point out the similarities and common physics in Galactic black hole X-ray binaries and active galactic nuclei, and demonstrate that the black hole mass estimation is very much helpful to understand the accretion physics around black holes.     

Hawking temperature and thermodynamics geometry of the 3D charged-dilaton black holes

In this Letter, we first investigate the Hawking temperature of the 3D charged-dilaton black holes by using the Generalized Uncertainty Principle. The results show that corresponding to the minimum radius of the event horizon, with the order of the Planck scale, there is a minimum mass or remnant for this type of black holes. Then, we study the thermodynamics geometry of the 3D charged-dilaton black holes. We find that the Weinhold geometry of the 3D charged-dilaton black holes is curved, whereas its Ruppeiner geometry is flat. Finally, we calculate the heat capacity of the black holes, and obtain the phase transition point.     

Accretion onto Charged Black Holes in Einstein and Massive Theories of Gravity *

The accretion process is being investigated onto some important black holes such as Born-Infeld-AdS black hole, non-linear charged black hole solution in AdS space-time and Einstein-Yang-Mills massive gravity in the presence of Born-Infeld nonlinear electrodynamics. We find out the relations of radial velocity, energy density and change of mass for mention black holes and analyze their behavior graphically for different values of equation of state parameters $\omega$. We also examine the relations for critical speed for these black holes. It is observed that for different state parameters different fluids exhibit different evolutions in black holes backgrounds. The energy density of some fluids is negative or positive near the black hole while other fluids become cause to increase or decrease in black hole mass.     

Primordial braneworld black holes: Significant enhancement of lifetimes through accretion

The Randall-Sundrum (RS-II) braneworld cosmological model with a fraction of the total energy density in primordial black holes is considered. Due to their 5d geometry, these black holes undergo modified Hawking evaporation. It is shown that during the high-energy regime, accretion from the surrounding radiation bath is dominant compared to evaporation. This effect increases the mass of the black holes till the onset of matter (or black hole) domination of the total energy density. Thus black holes with even very small initial masses could survive till several cosmologically interesting eras.     

激光干涉引力波天文台探测到的引力波事件中的黑洞

2016年2月11日,激光干涉引力波天文台(LIGO)发布了震惊世界的科学新闻：爱因斯坦100年前预言的引力波终于被人类探测到了！而且这个引力波事件GW150914来自于两个恒星级质量黑洞的并合！众多大众和专业媒体都对此做了大量的报道和介绍,引起了大众的普遍关注,因此文章将从不同的角度简要回答有关产生这个引力波事件中的两个黑洞的几个问题：为什么爱因斯坦不相信黑洞存在？怎么知道这样的天体是黑洞？物质是如何掉到黑洞里面的？如何获得独立的证据证明这样的引力波事件的确来自于黑洞的并合？探测这样的引力波事件对于我们理解黑洞有什么进一步的作用？     

Discrete Spectra of Charged Black Holes

Bekenstein proposed that the spectrum of horizon area of quantized black holes must be discrete and uniformly spaced. We examine this proposal in the context of spherically symmetric charged black holes in a general class of gravity theories. By imposing suitable boundary conditions on the reduced phase space of the theory to incorporate the thermodynamic properties of these black holes and then performing a simplifying canonical transformation, we are able to quantize the system exactly. The resulting spectra of horizon area, as well as that of charge are indeed discrete. Within this quantization scheme, near-extremal black holes (of any mass) turn out to be highly quantum objects, whereas extremal black holes do not appear in the spectrum, a result that is consistent with the postulated third law of black hole thermodynamics.     

临界中性Gauss-Bonnet-anti-de Sitter黑洞复杂度演化

利用Fan和Liang(Fan Z Y,Liang H Z 2019 Phys.Rev.D 100086016)研究一般高阶导数引力复杂度的方法,对临界中性Gauss-Bonnet-anti-de Sitter(Gauss-Bonnet-anti-de Sitter,AdS)黑洞的复杂度演化进行研究,并且将研究结果和一般中性Gauss-Bonnet-AdS黑洞的结果进行了比较.研究发现,二者的复杂度演化的整体规律是一致的,它们的主要区别在无量纲的临界时间上.对于五维的临界中性Gauss-Bonnet-AdS黑洞,当黑洞视界面为平面或者球面时,不同大小的黑洞的无量纲的临界时间相同,都取到了最小值.当维度超过五维时,不同大小的球对称临界中性Gauss-Bonnet-AdS黑洞的无量纲临界时间的差异明显要比一般的情况小.这些差异很可能和中性Gauss-Bonnet-AdS黑洞的临界性有关.     

Spectroscopies of Extreme Black Holes

The spectroscopies of extreme black holes are investigated by the intrinsic property of these black holes in this paper. We find that the area spectrum of the extreme Reissner-Nordstrom black hole is dependent on the fine structure constant. While the area spectra share the same expression and are determined by the quantum numbers of angular momentum for the extreme Kerr-Sen Dilaton-Axion and Kaluza-Klein black holes.     

Hawking radiation of linear dilaton black holes

We compute exactly the semi-classical radiation spectrum for a class of non-asymptotically flat charged dilaton black holes, the so-called linear dilaton black holes. In the high frequency regime, the temperature for these black holes generically agrees with the surface gravity result. In the special case where the black hole is massless, we show that, although the surface gravity remains finite, there is no radiation, in agreement with the fact that massless objects cannot radiate.     

Regular black holes with improved energy conditions and their analogues in fluids

On the premise of the importance of energy conditions for regular black holes, we propose a method to remedy those models that break the dominant energy condition, e.g., the Bardeen and Hayward black holes. We modify the metrics but ensure their regularity at the same time, so that the weak, null, and dominant energy conditions are satisfied, with the exception of the strong energy condition. Likewise, we prove a no-go theorem for conformally related regular black holes, which states that the four energy conditions can never be met in this class of black holes. In order to seek evidences for distinguishing regular black holes from singular black holes, we resort to analogue gravity and regard it as a tool to mimic realistic regular black holes in a fluid. The equations of state for the fluid are solved via an asymptotic analysis associated with a numerical method, which provides a modus operandi for experimental observations, in particular, the conditions under which one can simulate realistic regular black holes in the fluid.     

经典Kerr黑洞和量子Kerr黑洞系统的微正则系综理论描述与统计“自举”条件

分别从Kerr黑洞的经典谱和量子谱出发，建立了一个居于微正则系综理论描述的系统态密度 的不等式，并由此证明了Kerr黑洞满足统计“自举(bootstrap)”条件.其主要结论是对于由 大量Kerr黑洞组成的体系，在高能极限下，最可能的构型是一个黑洞将获得系统所有的质量 和全部的角动量，而且转动不会破坏黑洞的“自举”性质. 关键词： Kerr黑洞 统计“自举”问题     

Acceleration of particles in Einstein-Maxwell-dilaton black holes

It has recently been pointed out that, under certain conditions, the energy of particles accelerated by black holes in the center-of-mass frame can become arbitrarily high. In this paper, we study the collision of two particles in the case of four-dimensional charged nonrotating, extremal charged rotating and near-extremal charged rotating Kaluza-Klein black holes as well as the naked singularity case in Einstein-Maxwell-dilaton theory. We find that the center-of-mass energy for a pair of colliding particles is unlimited at the horizon of charged nonrotating Kaluza-Klein black holes, extremal charged rotating Kaluza-Klein black holes and in the naked singularity case.     

Kerr black holes are not fragile

Certain AdS black holes are “fragile”, in the sense that, if they are deformed excessively, they become unstable to a fundamental non-perturbative stringy effect analogous to Schwinger pair-production [of branes]. Near-extremal topologically spherical AdS-Kerr black holes, which are natural candidates for string-theoretic models of the very rapidly rotating black holes that have actually been observed to exist, do represent a very drastic deformation of the AdS-Schwarzschild geometry. One therefore has strong reason to fear that these objects might be “fragile”, which in turn could mean that asymptotically flat rapidly rotating black holes might be fragile in string theory. Here we show that this does not happen: despite the severe deformation implied by near-extremal angular momenta, brane pair-production around topologically spherical AdS-Kerr-Newman black holes is always suppressed.