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.     

Energy,momentum and angular momentum of gravitational radiation from a particle plunging into a non-rotating black hole

We have computed the energy ΔE, the momentum ΔP and the angular momentum ΔJ of gravitational radiation induced by a particle of mass μ and angular momentum μL_z plunging into a Schwarzschild black hole of mass M (?μ). It is found that the maximum value of ΔP is 4.5 × 10^?2 (μ/M) μc, ΔE/ΔJ ≈ 0.15c/(GM/c²), and a rotating ring plunging into a black hole emits less energy than a non-rotating one.     

Gravitational radiation induced by a particle falling along the Z-axis into a Kerr black hole

We have computed the spectrum and the energy of gravitational radiation induced by a test particle of mass μ falling along the z-axis into a Kerr black hole of mass M(? μ) and angular momentum Ma(a < M). It is found that the total energy radiated is 0.0170 0.0170 μc²μM when α = 0.99M, which is 1.65 times larger than that when α = 0, i.e., the Schwarzschild black hole case.     

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.     

Effective Lagrangian for quantum black holes

We discuss the most general effective Lagrangian obtained from the assumption that the degrees of freedom to be quantized, in a black hole, are on the horizon. The effective Lagrangian depends only on the induced metric and the extrinsic curvature of the (fluctuating) horizon, and the possible operators can be arranged in an expansion in powers of M_P1/M, where M_P1 is the Planck mass and M the black hole mass. We perform a semiclassical expansion of the action with a formalism which preserves general covariance explicitly. Quantum fluctuations over the classical solutions are described by a single scalar field living in the (2 + 1)-dimensional world-volume swept by the horizon, with a given coupling to the background geometry. We discuss the resulting field theory and we compute the black hole entropy with our formalism.     

Scattering of Hawking photons as a barrier to particle absorption by black holes

Electromagnetic scattering interactions between photons emanating from a Schwarzschild black hole and an incident charged particle should generate a repulsive force between the particle and black hole. The net scattering cross-section is calculated here as a function of the mass M of the black hole and the mass m of the particle for scenarios in which the particle is point-like and initially stationary, with proper energy ε=m, at some location far from the black hole. It follows from comparing the repulsive scattering force to the corresponding gravitational force that, in order for the particle to be drawn to the black hole, ε/Tbh must be greater than a certain lower bound that is of the order ¹⁰−3 for spin-1/2 or spin-0 particles with unit-charge. Although the scattering restriction is weaker than the requirement ε/Tbh?1 obtained independently from field-theoretic and thermodynamic treatments, the recurrence of a lower bound on the Boltzmann factor ε/Tbh in limitations on particle absorption suggests a physical unity whose nature is fundamentally thermodynamic.     

Gravitational radiation from a particle with zero orbital angular momentum plunging into a Kerr black hole

We have computed the energy ΔE, the momentum ΔP and the angular momentum ΔJ of gravitational radiation induced by a particle of mass μ and of zero orbital angular momentum plunging in the θ = π/2 plane into a Kerr black hole of mass M(?μ) and angular momentum Ma. It is found that ΔE for a = 0.99M is 4.45 × 10^-2 (μ²/M)c², which is 4.27 times larger than that for the a = 0 case.     

Corrected Entropy of BTZ Black Holes

In this paper, corrected entropy of a class of BTZ black holes, include charge and rotation, studied. We obtain corrected Bekenstein-Hawking entropy and find that effect of charge viewed at order A ^?2, and effect of rotation viewed at order A ^?6, therefore Q and J don’t have contribution in corrected entropy lower than the second order. We also write the first law of black hole thermodynamics for the case of charged rotating BTZ black hole.     

Klein paradox in a kerr geometry

The crossing of the classical positive and negative energy states E⁺ and E^? introduced by Christodoulou-Ruffini and interpreted within the framework of a relativistic quantum field theory by Deruelle and Ruffini, leads to a Klein paradox. It has been shown by Euler and Heisenberg that when the transmission coefficient T² through the barrier between the E⁺ and E^? states is small it is proportional to the probability of pair creation. Numerical computations show that, in the case of a small Kerr black hole (GM/c² ??/muc), the probability of pair creation of particles of mass μ is maximum when $\text{E ～ ?Ω}$, where E is the energy of the created particles and Ω and M the angular velocity and the mass of the back hole.     

Dark viscous fluid coupled with dark matter and future singularity

Motivated by Kerner and Man’s fermions tunneling method of dimension 4 black holes, in this paper, we further improve the analysis to investigate Hawking radiation of charged Dirac particles with spin 1/2 from general non-extremal rotating charged black holes with two parameters and a non-zero cosmological constant in minimal five-dimensional gauged supergravity. For space-times with different horizon topology and different dimensions, constructing a set of appropriate γ ^μ matrices for general covariant Dirac equation is an important technique for the fermion tunneling method. By introducing a set of appropriate matrices γ ^μ and employing the ansatz for the spin-up spinor field, we successfully recovered the tunneling probability of charged Dirac particles and the expected Hawking temperature of the black hole, which is exactly consistent with that obtained by other methods. Moreover, the fermion tunneling method can be directly applied to the other five-dimensional charged black holes, which strengthens the validity and power of the fermion tunneling method.     

Rotating dirty black hole and its shadow

In this paper, we examine the effect of dark matter to a Kerr black hole of mass m. The metric is derived using the Newman-Janis algorithm, where the seed metric originates from the Schwarzschild black hole surrounded by a spherical shell of dark matter with mass M and thickness Δr_s. The seed metric is also described in terms of a piecewise mass function with three different conditions. Specializing in the non-trivial case where the observer resides inside the dark matter shell, we analyzed how the effective mass of the black hole environment affects the basic black hole properties. A high concentration of dark matter near the rotating black hole is needed to have considerable deviations on the horizons, ergosphere, and photonsphere radius. The time-like geodesic, however, shows more sensitivity to deviation even at very low dark matter density. Further, the location of energy extraction via the Penrose process is also shown to remain unchanged. With how the dark matter distribution is described in the mass function, and the complexity of how the shadow radius is defined for a Kerr black hole, deriving an analytic expression for Δr_s as a condition for notable dark matter effects to occur remains inconvenient.     

Stochastic evolution of Schwarzschild black hole in a radiation heat bath

The mass of a Schwarzschild black hole in equilibrium with black-body radiation is shown to undergo a random drift with a diffusion coefficient D ～ M^-3. This follows from the master equation for the radiation in a stochastically bistable system of a black hole in an isolating cavity.     

Properties of a thin accretion disk around a rotating non-Kerr black hole

We study the accretion process in the thin disk around a rotating non-Kerr black hole with a deformed parameter and an unbound rotation parameter. Our results show that the presence of the deformed parameter ? modifies the standard properties of the disk. For the case in which the black hole is more oblate than a Kerr black hole, the larger deviation leads to the smaller energy flux, the lower radiation temperature and the fainter spectra luminosity in the disk. For the black hole with positive deformed parameter, we find that the effect of the deformed parameter on the disk becomes more complicated. It depends not only on the rotation direction of the black hole and the orbit particles, but also on the sign of the difference between the deformed parameter ?   and a certain critical value _?c${?}_c$. These significant features in the mass accretion process may provide a possibility to test the no-hair theorem in the strong-field regime in future astronomical observations.     

The electromagnetic energy with the truncation method for a five-dimensional rotating black hole in a uniform magnetic field

We consider a charged five-dimensional Myers–Perry black hole in a uniform magnetic (test) field. Using the Komar mass formula, we calculate the total energy of the electromagnetic field within the truncation three-sphere for a five-dimensional rotating black hole with two equal-rotation parameters and two equal-magnetic field strengths. We show that the total electromagnetic energy takes the minimum value when the five-dimensional rotating black hole acquires a non-zero net electric charge Q.     

Magnetic charge,black holes,and cosmic censorship

The possibility of converting a Reissner-Nordström black hole into a naked singularity by means of test particle accretion is considered. The dually charged Reissner-Nordström metric describes a black hole only when M² > Q³ + P². The test particle equations of motion are shown to allow test particles with arbitrarily large magnetic charge/mass ratios to fall radially into electrically charged black holes. To determine the nature of the final state (black hole or naked singularity) an exact solution of Einstein's equations representing a spherical shell of magnetically charged dust falling into an electrically charged black hole is studied. Naked singularities are never formed so long as the weak energy condition is obeyed by the infalling matter. The differences between the spherical shell model and an infalling point test particle are examined and discussed.     

Superradiant instability for black holes immersed in a magnetic field

We consider the bound states of the massive scalar field around a rotating black hole immersed in the asymptotically uniform magnetic field. In the regime of slow black hole rotation, the Klein–Gordon equation allows separation of variables. We show that the growth rate of the instability can be amplified a few times by the magnetic field. The effect occurs because the magnetic field adds the “effective mass” term B|m|$B|m|$ to the scalar field potential for a Kerr black hole. In addition, and as a by-product, we discuss the behavior of the quasinormal modes for the magnetized rotating black holes.     

Exotic decays of the muon and heavy leptons in gauge theories

We have studied the decay ?₁ → ?₂ + γ for arbitrary like charged spin $\text{1}\text{2}$ leptons in a manner which is applicable to a large class of models. Our computations assume that this process is induced by one loop diagrams. When the leading effect is cancelled by a leptonic G.I.M. mechanism, we find an extremely large enhancement of O(M_W⁴/M_L⁴) in Λ(μ^?→e^?+e⁺e^?)/Λ(μ^?→e^?+γ) if the intermediate lepton is charged.     

The gravitational searchlight effect from synchrotron radiation in the Schwarzschild geometry

Gravitational synchrotron radiation is studied using the techniques of geometrical optics. It is found that the geometry of the Schwarzschild black hole creates a rotating searchlight effect, even for a source particle which radiates only during an infinitesimally brief interval of coordinate time. The period of rotation of the searchlight is shown to provide a measurement of the mass of the blackhole, since the period T is related to the mass M by T = 2π27^1/2 M for the Schwarzschild geometry and by T = 4πM for the extreme (a = M) Kerr geometry.     

How to mine energy from a black hole

We describe a process by which energy literally can be mined from a black hole. We argue that the only limit placed by fundamental considerations on the rate at which energy can be extracted from a black hole by this process isdE/dt ～ 1 in Planck unitsG = c = ? = 1. This is far greater than the ratedE/dt ～ 1/M² at which the black hole spontaneously loses energy by Hawking radiation.