Stoytcho S. Yazadjiev

Uniqueness Theorem for 5-Dimensional Black Holes with Two Axial Killing Fields

We show that two stationary, asymptotically flat vacuum black holes in 5 dimensions with two commuting axial symmetries are identical if and only if their masses, angular momenta, and their “interval structures” coincide. We also show that the horizon must be topologically either a 3-sphere, a ring, or a Lens-space. Our argument is a generalization of constructions of Morisawa and Ida (based in turn on key work of Maison) who considered the spherical case, combined with basic arguments concerning the nature of the factor manifold of symmetry orbits.

Completely integrable sector in 5D Einstein-Maxwell gravity and derivation of the dipole black ring solutions

We consider 5D Einstein-Maxwell (EM) gravity in spacetimes with three commuting Killing vectors: one timelike and two spacelike Killing vectors one of them being hypersurface orthogonal. Assuming a special ansatz for the Maxwell field we show that the 2-dimensional reduced EM equations are completely integrable by deriving a Lax-pair presentation. We also develop a solution generating method for explicit construction of exact EM solutions with considered symmetries. We also derive explicitly a new rotating six parametric 5D EM solution which includes the dipole black ring solution as a particular case.

A Uniqueness Theorem for Stationary Kaluza-Klein Black Holes

We prove a uniqueness theorem for stationary D-dimensional Kaluza-Klein black holes with D − 2 Killing fields, generating the symmetry group

Kerr-Sen dilaton-axion black hole lensing in the strong deflection limit

{{\mathbb R}\times U(1)^{D-3}}

Shadow of a rotating traversable wormhole

. It is shown that the topology and metric of such black holes is uniquely determined by the angular momenta and certain other invariants consisting of a number of real moduli, as well as integer vectors subject to certain constraints.

Gravitational Lensing by Rotating Naked Singularities

Abstract In the presence of a complex scalar field scalar–tensor theory allows for scalarized rotating hairy black holes. We exhibit the domain of existence for these scalarized black holes, which is bounded by scalarized rotating boson stars and hairy black holes of General Relativity. We discuss the global properties of these solutions. Like their counterparts in general relativity, their angular momentum may exceed the Kerr bound, and their ergosurfaces may consist of a sphere and a ring, i.e., form an ergo-Saturn.

A uniqueness theorem for five-dimensional Einstein–Maxwell black holes

In the present work we study numerically quasiequatorial lensing by the charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the strong deflection limit. In this approximation we compute the magnification and the positions of the relativistic images. The most outstanding effect is that the Kerr-Sen black hole caustics drift away from the optical axis and shift in the clockwise direction with respect to the Kerr caustics. The intersections of the critical curves on the equatorial plane as a function of the black hole angular momentum are found, and it is shown that they decrease with the increase of the parameter Q{sup 2}/M. All of the lensing quantities are compared to particular cases as Schwarzschild, Kerr, and Gibbons-Maeda black holes.

Non-asymptotically flat, non-dS/AdS dyonic black holes in dilaton gravity

We derive exact magnetically charged, static, and spherically symmetric black hole solutions of the four-dimensional Einstein-Born-Infeld-dilaton gravity. These solutions are neither asymptotically flat nor (anti)-de Sitter. The properties of the solutions are discussed. It is shown that the black holes are stable against linear radial perturbations.