Violation of the second law of black hole physics by tachyons

It is shown that the interaction of a class of positive energy tachyons decreases the area of the horizon of theT-S, ∂=3 metric even in the case of a reversible transformation (M _ir=constant). This is a violation of the second law of black hole physics.     

The bending of light ray and unphysical solutions in general relativity

In general relativity, according to Einstein, a gauge is related to the time dilation and the space contractions, and thus a physically realizable gauge should be unique for a given frame of reference. Since more than one metric solution for the same frame can produce the same deflection angle, this means that an invalid space－time metric can produce the correct deflection angle for a light ray. To demonstrate this with an unambiguous example, we consider a new extreme case that there is no space contraction in the radius direction while the conditions of asymptotic flatness and the requirement for gravitational red shifts are satisfied. This solution has a distinct characteristic of "space expansion" in the other directions. Nevertheless, it turns out that, in spite of requiring far more subtle calculations, the resulting deflection angle of a light ray is the same. An interesting property of this new solution is that its event horizon corresponds to an arbitrary integral constant. Thus, this calculation demonstrates beyond doubt that an unphysical solution can produce the correct first-order approximation of light bending. This makes it clear that there is a main difference between local effects such as the gravitational red shifts and the local light speeds, which are not gauge invariant, and integrated effects such as the bending of light, which can be (restricted) gauge invariant.     

Tachyons in general relativity

The tachyonic version of the Schwarzschild (bradyonic) gravitational field within the framework of extended relativity is considered. The metric of a tachyonic black hole is obtained through superluminal transformations from a bradyonic metric. The extended space-time manifold of this geometry which includes both black and white tachyonic holes is analysed, and the differences between the tachyonic and bradyonic versions are noted. It is shown that the meanings of black holes, tachyons and bradyons depend on the character of the reference frame and are not absolute.     

Gravitational radiation fields in teleparallel equivalent of general relativity and their energies

We derive two new retarded solutions in the teleparallel theory equivalent to general relativity (TEGR).One of these solutions gives a divergent energy.Therefore,we use the regularized expression of the gravitational energymomentum tensor,which is a coordinate dependent.A detailed analysis of the loss of the mass of Bondi space-time is carried out using the flux of the gravitational energy-momentum.     

彭罗斯对广义相对论和黑洞理论的贡献

这篇文章列出了2020年诺贝尔物理学奖获得者彭罗斯对广义相对论和黑洞理论做出的重要贡献.它包括著名的奇点定理、彭罗斯图、彭罗斯过程和宇宙监督假设等.介绍了彭罗斯和霍金之间的友谊和合作.也简要介绍了另两位2020年诺贝尔物理学奖获得者根泽尔和盖兹对存在于银河系中心的超大质量致密天体的发现.     

Status of numerical relativity

I describe the current status of numerical relativity from my personal point of view. Here, I focus mainly on explaining the numerical implementations necessary for simulating general relativistic phenomena such as the merger of compact binaries and stellar collapse, emphasizing the well-developed current status of such implementations that enable simulations for several astrophysical phenomena. Some of our latest results for simulation of binary neutron star mergers are briefly presented.     

Entropy of a Uniformly Accelerating Black Hole

Kinnersley has discussed the space–time of an arbitrarily accelerating point mass. We select a simple case in which the black hole is uniformly accelerated and the mass does not vary with time. We adopt thin film brick-wall model to calculate the entropy of black hole. We find that both the temperature and the entropy density of black hole can be calculated at every point on the horizon. This result indicates that the conclusion that black hole entropy is proportional to its area can be applied to horizon not only globally, but also locally.     

Motion of extended bodies in general relativity and gravitational radiation

In the framework of general relativity, we consider the motion of extended spherically symmetric bodies coupled together only by gravitational interactions. The self-gravitational radiation of the bodies is taken into account. The problem is solved by the Fock method of successive approximations in harmonic coordinates, assuming slow motion and weak fields (v²/c² U/c^{2 2} 1) with terms up to and including the fifth order in taken into account. The equations of motion of the two bodies are derived, including the gravitational radiation reaction terms. It is shown that the system is conservative up to fifth order but to second order in e the six classical integrals of the motion are replaced by only two (the total energy and total angular momentum). An induced rotation effect in a system of initially nonrotating bodies is obtained. It is shown that in the fifth order approximation the system is nonconservative because of gravitational radition. An expression is obtained for the rate of loss of energy from the system directly from the equations of motion.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 12–16, January, 1985.     

Electrodynamic radiation reaction and general relativity

We argue that the well-known problem of the instabilities that are associated with the self-forces (radiation reaction forces) in classical electrodynamics are possibly stabilized by the introduction of gravitational forces via general relativity.     

Hawking Radiation of Dirac Particles in a Nonuniformly Rectilinearly Accelerating Black Hole

The Hawking radiation of Dirac particles on the event horizon of a nonuniformly rectilinearly accelerating black hole is studied in this paper. First, we construct the symmetrized null tetrad from which the spin coefficients and Dirac equation are derived. Next, by proposing generalized tortoise coordinate transformation, the decoupling problem of the Dirac equation with nonzero rest mass is solved. Finally, by analytic continuation, the Hawking thermal spectrum formula of Dirac particle for nonuniformly rectilinearly accelerating black hole is obtained.     

Dynamics of extended bodies in general relativity center-of-mass description and quasirigidity

Dixon's approach to describe the dynamics of extended bodies in metric theories of gravity is elaborated. The exact, general relation between the center-of-mass 4-velocity and the 4-momentum is derived. Quasirigid bodies are defined, and their equations of motion are shown to be determinate for a given metric. Multipole approximations are considered, and the physical meaning of quasirigidity is investigated by establishing an approximate connection with continuum mechanics.     

Thermodynamics of the black holes under the extended generalized uncertainty principle with linear terms

In this paper, we employ the extended generalized uncertainty principle with linear terms (LEGUP) to investigate the thermodynamics properties of the Schwarzschild and Reissner–Nordström (RN) black holes. Firstly, by constructing the theoretical framework of LEGUP, the minimal temperature of the Schwarzschild black hole and the modified mass–temperature function for the black hole are calculated. Furthermore, the heat capacity function for the Schwarzschild black hole is obtained. After that, we compare LEGUP black hole thermodynamics with EGUP black hole and with the usual forms. Besides, the modification of black hole entropy is discussed, which involves a heuristic analysis of particles absorbed by the black hole. Finally, we derive the LEGUP-corrected temperature, heat capacity and entropy functions of the RN black hole.     

爱因斯坦和相对论的诞生与发展

简要介绍了爱因斯坦的生平和相对论的创立与发展,以及相对论研究的现状与面临的困难．     

带有电荷与磁荷的直线加速动态黑洞的熵

带有电荷与磁荷的一类直线加速黑洞视界表面各点的温度不相同.采用薄膜模型计算出每点的熵密度进而得到总熵与视界面积成正比的结论.所采用的截断因子可以用视界面上的温度表示 关键词： 熵 加速动态黑洞 薄膜模型     

电磁直线加速动态黑洞时空中Dirac粒子的Hawking辐射

研究了作直线加速运动的电磁黑洞视界面上Dirac粒子的Hawking 辐射.首先，构造对称化零 标架，计算旋系数，导出Dirac方程，并对其进行化简.然后，通过引入广义乌龟坐标，在视 界面上将Dirac方程退耦.利用Damour-Ruffini方法，求出了温度以及热谱公式，并对所得结 果进行了讨论. 关键词： 加速动态黑洞 Dirac粒子 Dirac方程 Hawking辐射     

The Shell of Incoherent Charged Matter Falling onto a Charged Rotating Black Hole

The motion of the shell of charged testparticles falling radially from rest at infinity withzero total angular momentum onto a Kerr–Newmanblack hole is studied. The shell, initially spherical,becomes prolate along the axis of symmetry of the holeduring the fall. The shape of the shell from theviewpoint of distant observers is characterized by meansof the photons moving along geodesics of the outgoing principal null congruence. The motion of theshell is examined analytically for large distances andnear the horizon. In the special case, when at largedistances of the hole the attractive Newtongravitational force is compensated by the repulsive Coulombforce, the complete motion is given explicitly in termsof elementary functions.     

The relation between a black hole and a general blackbody system

Taking a black hole as a black body system, using general black body radiation theory, a Schwarzschild black hole and a Kerr--Newman black hole are investigated respectively. It is concluded that a black hole can be regarded as an ideal general black body system exactly for the changing process only. However, a stationary global black hole cannot be smoothly regarded as a general black body system. A black hole has some special characteristics which different from a general thermodynamics system. This conclusion means that a black hole should be inherently dynamical, at least when it is taken as a black body system.     

直线加速运动动态黑洞的熵

选取超前爱丁顿坐标,采用薄膜brickwall模型,计算Kinnersley度规表述的直线加速运动动态黑洞的熵.通过此方法,可以给出视界面上每一点的温度和熵密度.这一结果表明,熵与视界面积成正比的结论,不仅适用于整个视界,也适用于视界面上的局部;不仅适用于稳态黑洞,也适用于动态黑洞.在薄膜趋于视界面时,其厚度也趋于零,薄膜本身成为视界面,黑洞熵就是视界面上量子态的熵 关键词： 熵 加速黑洞 薄膜brickwall模型