199 citations
- Sofia University "St. Kliment Ohridski"BG36 papers
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- University of Chemical Technology and MetallurgyBG5 papers
- University of TübingenDE4 papers
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11 papers · 1 filter
Mass-spin relation of black holes obtained by twin high-frequency quasi-periodic oscillations
Ivan Zhivkov Stefanov
The paper studies the uniqueness and the monotonicity of the mass-spin relation of black holes the X-ray power density spectra of which contain twin high-frequency quasi-periodic o…
Gravitational Lensing by Phantom Black holes
Galin N. Gyulchev, Ivan Zh. Stefanov
In some models dark energy is described by phantom scalar fields (scalar fields with "wrong" sign of the kinetic term in the lagrangian). In the current paper we study the effect o…
Time Evolution of the Radial Perturbations and Linear Stability of Solitons and Black Holes in a Generalized Skyrme Model
Daniela D. Doneva, Kostas D. Kokkotas, Ivan Zh. Stefanov +1
We study the time evolution of the radial perturbation for self-gravitating soliton and black-hole solutions in a generalized Skyrme model in which a dilaton is present. The backgr…
Solitons and Black Holes in a Generalized Skyrme Model with Dilaton-Quarkonium field
Daniela D. Doneva, Ivan Zh. Stefanov, Stoytcho S. Yazadjiev
Skyrme theory is among the viable effective theories which emerge from low-energy limit of quantum chromodynamics. Many of its generalizations include also a dilaton. Here we find…
Quasi-normal modes, bifurcations and non-uniqueness of charged scalar-tensor black holes
Daniela D. Doneva, Stoytcho S. Yazadjiev, Kostas D. Kokkotas +1
In the present paper we study the scalar sector of the quasinormal modes of charged general relativistic, static and spherically symmetric black holes coupled to nonlinear electrod…
Connection between black-hole quasinormal modes and lensing in the strong deflection limit
Ivan Zh. Stefanov, Stoytcho S. Yazadjiev, Galin G. Gyulchev
The purpose of the current Letter is to give some relations between gravitational lensing in the strong-deflection limit and the frequencies of the quasinormal modes of spherically…