Andrey A. Shoom

Critical escape velocity for a charged particle moving around a weakly magnetized Schwarzschild black hole

We discuss charged particles motion in a spacetime of a weakly magnetized static non-rotating black hole. We study under which conditions a charged particle originally revolving around the black hole at a circular orbit after being kicked by another particle or photon can escape to infinity. We determine the escape velocity for particles at the innermost stable circular orbits and discuss the properties of particles moving with near-critical velocity. We show that in a general case such a motion is chaotic.

Local Invariants Vanishing on Stationary Horizons: A Diagnostic for Locating Black Holes

Inspired by the example of Abdelqader and Lake for the Kerr metric, we construct local scalar polynomial curvature invariants that vanish on the horizon of any stationary black hole: the squared norms of the wedge products of n linearly independent gradients of scalar polynomial curvature invariants, where n is the local cohomogeneity of the spacetime.

Interior of a Charged Distorted Black Hole

We study the interior of a charged, nonrotating distorted black hole. We consider static and axisymmetric black holes, and focus on a special case when an electrically charged distorted solution is obtained by the Harrison-Ernst transformation from an uncharged one. We demonstrate that the Cauchy horizon of such a black hole remains regular, provided the distortion is regular at the event horizon. The shape and the inner geometry of both the outer and inner (Cauchy) horizons are studied. We demonstrate that there exists a duality between the properties of the horizons. Proper time of a free fall of a test particle moving in the interior of the distorted black hole along the symmetry axis is calculated. We also study the property of the curvature in the inner domain between the horizons. Simple relations between the 4D curvature invariants and the Gaussian curvature of the outer and inner horizon surfaces are found.

Gregory-Laflamme instability of 5D electrically charged black strings

We study the Gregory-Laflamme instability of 5D compactified, electrically charged black strings. We consider static, linear perturbations of these solutions and derive a master equation for these perturbations. Using numerical analysis we search for the threshold unstable modes and derive the critical wavelength. The results are illustrated in the black string mass vs electric charge phase diagram. A similar diagram is constructed using the global thermodynamic equilibrium argument applied to the charged string and 5D electrically charged black hole. The results derived illustrate that an electric charge makes the black string less stable.

Distorted five-dimensional vacuum black hole

In this paper we study how the distortion generated by a static and neutral distribution of external matter affects a five-dimensional Schwarzschild-Tangherlini black hole. A solution representing a particular class of such distorted black holes admits an ℝ 1 × U(1) × U(1) isometry group. We show that there exists a certain duality transformation between the black hole horizon surface and the stretched singularity surface. The space-time near the distorted black hole singularity has the same topology and Kasner exponents as those of a five-dimensional Schwarzschild-Tangherlini black hole. We calculate the maximal proper time of free fall of a test particle from the distorted black hole horizon to its singularity and find that, depending on the distortion, it can be less, equal to, or greater than that of a Schwarzschild-Tangherlini black hole of the same horizon area. This implies that due to the distortion, the singularity of a Schwarzschild-Tangherlini black hole can come close to its horizon. A relation between the Kretschmann scalar calculated on the horizon of a five-dimensional static, asymmetric, distorted black hole and the trace of the square of the Ricci tensor of the horizon surface is derived.

Scattering of circularly polarized light by a rotating black hole

We study scattering of polarized light by a rotating (Kerr) black hole of the mass M and the angular momentum J. In order to keep trace of the polarization dependence of photon trajectories one can use the following dimensionless parameter:

PARTICLE DYNAMICS IN WEAKLY CHARGED EXTREME KERR THROAT

\varepsilon=\pm (\omega M)^{-1}

Radiation from an emitter revolving around a magnetized nonrotating black hole

, where

Distorted stationary rotating black holes

\omega

Geometric properties of static Einstein-Maxwell dilaton horizons with a Liouville potential

is the photon frequency and the sign + (-) corresponds to the right (left) circular polarization. We assume that