MASSIVE SCALAR PARTICLE IN THE GRAVITATIONAL FIELD OF A MICROCOSMIC BLACK HOLE

The finite motion of a massive scalar particle in the gravitational field of a microcosmic black hole with weak relativistic approximation is discussed. In the Schwarzschild field, using the condition for balance σ=0, we obtain the relation between the produced and captured amplitudes for particles. In the Kerr field we show that the attenuation depends on the moment of the black hole and the attenuation process becomes an exciting one when ωh.     

An Analytic Approximation for Researching Tunneling Rate from Black Hole in Proca Field

The analytic solution of a static spherical symmetrical Proca black hole is discussed in this paper. As in the massive vector field, Proca black hole can be considered as the analogy of RN background plus a perturbation with the same order as μ ² due to the mass of vector particle μ satisfying μ ² ? 1. Through the action of Proca field, we find the analytic form with the first and arbitrary order approximation. Furthermore, we divide the results into 3 groups according to the real zero solutions of the background (i.e., spacetime in massless vector field). Finally we analyze the Hawking radiation of such black hole, which is significant for constructing black hole thermodynamic.     

Binary black hole in a double magnetic monopole field

Ambient magnetic fields are thought to play a critical role in black hole jet formation. Furthermore, dual electromagnetic signals could be produced during the inspiral and merger of binary black hole systems. In this paper, we derive the exact solution for the electromagnetic field occurring when a static, axisymmetric binary black hole system is placed in the field of two magnetic or electric monopoles. As a by-product of this derivation, we also find the exact solution of the binary black hole configuration in a magnetic or electric dipole field. The presence of conical singularities in the static black hole binaries represent the gravitational attraction between the black holes that also drag the external two monopole field. We show that these off-balance configurations generate no energy outflows.     

Particle acceleration and curvature TeV emission by rotating, supermassive black holes

It is shown that particles accelerating near the event horizon of a spinning supermassive black hole that is threaded by externally supported magnetic field lines suffer severe curvature losses that limit the maximum energy they can attain to values well below that imposed by the maximum voltage drop induced by the black hole dynamo. It is further shown that the dominant fraction of the rotational energy extracted from the black hole is radiated in the TeV band. The implications for vacuum breakdown and the observational consequences are discussed.     

轴对称黑洞的量子统计熵

避开了求解黑洞背景下波动方程的因难,应用量子统计方法,通过应用在量子引力中、由广义测不准关系得出的新态密度方程,直接求解轴对称Kerr黑洞背景下玻色场和费米场的配分函数.然后,在视界附近计算黑洞背景下玻色场和费米场的熵.得到用收敛级数表达的黑洞熵.在计算中不存在用brick wall模型计算黑洞熵时出现的发散项和小质量近似,使人们对非球对称时空中黑洞的统计熵有更深入的认识. 关键词： 量子统计 非球对称时空 广义测不准关系 黑洞熵     

Dynamics of Particles Around a Regular Black Hole with Nonlinear Electrodynamics

We investigate the dynamics of a charged particle being kicked off from its circular orbit around a regular black hole by an incoming massive particle in the presence of magnetic field. The resulting escape velocity, escape energy and the effective potential are analyzed. It is shown that the presence of even a very weak magnetic field helps the charged particles in escaping the gravitational field of the black hole. Moreover the effective force acting on the particle visibly reduces with distance. Thus particle near the black hole will experience higher effective force as compared to when it is far away.     

Entropy of Kerr-Newman Black Hole to All Orders in the Planck Length

Using the quantum statistical method, the difficulty of solving the wave equation on the background of the black hole is avoided. We directly solve the partition functions of Bose and Fermi field on the background of an axisymmetric Kerr-Newman black hole using the new equation of state density motivated by the generalized uncertainty principle in the quantum gravity. Then near the black hole horizon, we calculate entropies of Bose and Fermi field between the black hole horizon surface and the hypersurface with the same inherent radiation temperature measured by an observer at an infinite distance. In our results there are not cutoffs and little mass approximation introduced in the conventional brick-wall method. The series expansion of the black hole entropy is obtained. And this series is convergent. It provides a way for studying the quantum statistical entropy of a black hole in a non-spherical symmetric spacetime.     

Black Hole Entropies of the Thin Film Model and the Membrane Model Without Cutoffs

Taking into account the effect of the generalized uncertainty principle on the generalized black hole entropy and tacking the thin film brick-wall model, we calculate the entropy of the quantum scalar field in generalized static black hole. The Bekenstein–Hawking entropies of all well-known static black holes are obtained. The entropy of 2-D membrane just at the event horizon of static black hole is also calculated, and the result of the black hole entropy proportional to the event horizon area can be obtained more easily and generally. This discussion shows that black hole entropy is just identified with the entropy of the quantum field on the event horizon. The difference from the original brick-wall model is that the present result is convergent without any cutoff and the little mass approximation is removed. With residue theorem, the integral difficulty in the calculation of black hole entropy is overcome.     

广义不确定关系与整体单极黑洞Dirac场的熵

将广义不确定关系引入新的态密度方程，采用WKB近似方法，对含整体单极黑洞Dirac场的熵进行了直接计算，所得黑洞熵与它的视界面积成正比，以此揭示了黑洞熵是其视界面处量子态的熵.与brick-wall模型方法不同，该结果不需要取任何截断.同时表明，用此方法不仅可以计算黑洞标量场的熵，而且可以计算Dirac场的熵.     

Stationary electromagnetic fields around black holes

In the framework of the Newman-Penrose formalism the electromagnetic field of a general stationary source occurring in the vicinity of a Schwarzschild black hole is obtained in the test-field approximation. The field is expressed in terms of hypergeometric functions (radial parts) and spin-s spherical harmonics (angular parts) both outside and inside the radius at which the source is, located. As examples, the fields of point charges, charged rings, current loops and magnetic dipoles (generally located in non-axisymmetric positions) are calculated.     

Quasinormal Modes of Electromagnetic Perturbation around a Stringy Black Hole

We investigate the electromagnetic perturbation around a stringy black hole. A second-order differential equation is obtained for the perturbation. The variation of the effective potential with r is presented. The complex frequencies of the quasinormal modes of electromagnetic perturbation around a stringy black hole are computed by the third Wentzel-Kramers-Brillouin （WKB） approximation. The results show that the parameters resulted from the compactification of higher dimensions can influence the quasinormal complex frequencies, and the Maxwell field around a stringy black hole damps more slowly than that around a Schwarzschild black hole.     

Black hole in an asymmetric electromagnetic field: New ponderomotive effects — Spin precession and drift

Two new ponderomotive effects in black hole physics are indicated: (i) the precession of the rotation axis of a charged black hole in an external magnetic field, (ii) the drift of a non-charged rotating hole in an asymmetric homogeneous electromagnetic field posessing a non-zero Poynting vector. The precession time for a black hole of solar mass with Q = 10^?5M in a magnetic field B ～ 10¹²G is about a year.     

Gravitational energy of a magnetized Schwarzschild black hole: a teleparallel approach

We investigate the distribution of gravitational energy in the spacetime of a Schwarzschild black hole immersed in a cosmic magnetic field. This is done in the context of the teleparallel equivalent of general relativity, which is an alternative geometrical formulation of general relativity, where gravity is described by a spacetime endowed with torsion rather than curvature, whose fundamental field variables are tetrad fields. We calculate the energy enclosed by a two-surface of constant radius—in particular, the energy enclosed by the event horizon of the black hole. In this case we find that the magnetic field has the effect of increasing the gravitational energy as compared to the vacuum Schwarzschild case. We also compute the energy (i) in the weak magnetic field limit, (ii) in the limit of vanishing magnetic field, and (iii) in the absence of the black hole. In all cases our results are consistent with what should be expected on physical grounds.     

Black holes in massive gravity: quasi-normal modes of scalar perturbations

We have studied quasinormal modes of scalar perturbations of a black hole in massive gravity. The parameters of the theory, such as the mass of the black hole, the scalar charge of the black hole and the spherical harmonic index is varied to see how the corresponding quasinormal frequencies change. We have also studied the massive scalar field perturbations. Most of the work is done using WKB approach while sections are devoted to compute quasinormal modes via the unstable null geodesics approach and the Pöschl–Teller approximation. Comparisons are done with the Schwarzschild black hole.     

Hawking Radiation of Charged and Magnetized Particles from the Kerr-Newman-Kasuya Black Hole via Covariant Anomaly

Hawking radiation of a particle with electric and magnetic charges from the Kerr-Newman-Kasuya black hole is discussed in the dragging coordinate frame via the anomaly cancellation method, initiated by Robinson and Wilczek. We redefine an equivalent charge of the charged and magnetized black hole by reconstructing the electromagnetic field tensor. We adopt the refined covariant anomaly cancellation method to determining the compensating fluxes of charge flow and energy momentum tensor, which are proved to precisely match with those of the 2-dimensional blackbody radiation at the Hawking temperature with an appropriate chemical potential.     

Accretion of a conducting medium onto a spherically symmetric black hole imbedded in a magnetic field

The relativistic motion of a conducting continuous medium in the vicinity of a black hole imbedded in a magnetic field is discussed. Expressions are obtained which characterize the variation of the magnetic field as a result of the accretion of matter.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 69–71, November, 1981.     

Quasinormal modes and absorption of a massless scalar field for the magnetic Gauss–Bonnet black hole

We study the massless scalar quasinormal frequencies of an asymptotically flat static and spherically symmetric black hole with a nonzero magnetic charge in four-dimensional extended scalar-tensor-Gauss–Bonnet theory. The results show that the real part of the quasinormal frequency becomes larger and the imaginary part becomes smaller with increasing the magnetic charge or the angular harmonic index. The existence of magnetic charges will reduce the damping of scalar perturbation, but increase the frequency. We also study the absorption cross-section of the scalar field in this black hole. We find that its curve will become lower as the magnetic charge increases, i.e. the magnetic charge will weaken the absorption capacity of the black hole. Meanwhile, the high-frequency limit of the total absorption cross-section is just the area of black hole shadow.     

Gamma-ray bursts from evaporating primordial black holes

It is believed that the detection of gamma-ray bursts from evaporating primordial black holes is highly improbable in the near future since the expected photon flux, consisting mainly of photons with energies ? GeV, is too low. Contrary to this point of view, we show that a large fraction of the black hole power at the final stage of evaporation (the last 10³ s) can be liberated as a burst of soft γ-ray emission of duration 10^?1–10³ s and luminosity 10²⁸–10³¹ erg/s in the energy range 0.1–1 MeV. According to our calculations of the black hole evaporation rate (within the Standard Model of elementary particles), when the black hole temperature exceeds approximately 10 GeV, the charged particle outflow from a black hole forms a well-defined plasma and can be described in the hydrodynamic approximation. In this case more than half of the rest energy of a black hole can be converted into soft gamma-rays due to the presence of the magnetic field with energy density comparable to that of charged particles. We consider various mechanisms leading to such transformation and estimate their efficiency. It is shown that, at least, some of the gamma-ray bursts detected by BATSE can be associated with evaporating black holes.