Static spherically symmetric black holes are discussed in the framework of higher dimensional gra... more Static spherically symmetric black holes are discussed in the framework of higher dimensional gravity with quadratic in curvature terms. Such terms naturally arise as a result of quantum corrections induced by quantum fields propagating in the gravitational background. We focus our attention on the correction of the form C 2 ¼ C C. The Gauss-Bonnet equation in four-dimensional spacetime enables one to reduce this term in the action to the terms quadratic in the Ricci tensor and scalar curvature. As a result the Schwarzschild solution which is Ricci flat will be also a solution of the theory with the Weyl scalar C 2 correction. An important new feature of the spaces with dimension D > 4 is that in the presence of the Weyl curvature-squared term a necessary solution differs from the corresponding ''classical'' vacuum Tangherlini metric. This difference is related to the presence of secondary or induced hair. We explore how the Tangherlini solution is modified by ''quantum corrections,'' assuming that the gravitational radius r 0 is much larger than the scale of the quantum corrections. We also demonstrated that finding a general solution beyond the perturbation method can be reduced to solving a single third order ordinary differential equation (master equation).
We consider the action principle to derive the classical, nonrelativistic motion of a self-intera... more We consider the action principle to derive the classical, nonrelativistic motion of a self-interacting particle in a 4D Lorentzian spacetime containing a wormhole and which allows the existence of closed time-like curves. For the case of a “hard-sphere” self-interaction potential we show that the only possible trajectories (for a particle with fixed initial and final positions and which traverses the wormhole once) minimizing the classical action are those which are globally self-consistent, and that the “principle of self-consistency” (originally introduced by Novikov) is thus a natural consequence of the “principle of minimal action.”
Journal of Cosmology and Astroparticle Physics, 2014
We consider weakly magnetized non-rotating black holes. In the presence of a regular magnetic fie... more We consider weakly magnetized non-rotating black holes. In the presence of a regular magnetic field the motion of charged particles in the vicinity of a black hole is modified. As a result, the position of the innermost stable circular orbit (ISCO) becomes closer to the horizon. When the Lorentz force is repulsive (directed from the black hole) the ISCO radius can reach the gravitational radius. In the process of accretion charged particles (ions) of the accreting matter can be accumulated near their ISCO, while neutral particles fall down to the black hole after they reach 6M radius. The sharp spectral line Fe Kα, emitted by iron ions at such orbits, is broadened when the emission is registered by a distant observer. In this paper we study this broadening effect and discuss how one can extract information concerning the strength of the magnetic field from the observed spectrum.
One of the methods of study of black holes in astrophysics is based on broadening of the spectrum... more One of the methods of study of black holes in astrophysics is based on broadening of the spectrum of radiation of ionized Iron atoms. The line Kα associated with Iron emission at 6.4 keV is very narrow. If such an ion is revolving around a black hole, this line is effectively broadened as a result of the Doppler and gravitational redshift effects. The profile of the broaden spectrum contains information about the gravitational field of the black hole. In the presence of a regular magnetic field in the vicinity of a black holes the characteristics of the motion of charged ions are modified. In particular, their innermost stable circular orbits become closer to the horizon. The purpose of this work is to study how this effect modifies the spectrum broadening of lines emitted by such an ion. Our final goal is to analyze whether the change of the spectrum profiles can give us information about the magnetic field in the black hole vicinity.
Physical review D: Particles and fields, Jan 15, 1989
The first part of the paper formulates general conditions (independent of a particular gaugetheor... more The first part of the paper formulates general conditions (independent of a particular gaugetheoretic model) under which a cylindrical distribution of matter can be joined to a vacuum exterior with a conical geometry and exhibits the relation between angular deficit and internal structure. To bring out the relation to gravitational mass, the second part is devoted to a detailed study of solutions of the initial-value problem for circular loops of string at a moment of time symmetry.
The general problem of finding the density matrices of particles and antiparticles produced by an... more The general problem of finding the density matrices of particles and antiparticles produced by an external electromagnetic field fron an arbitrary initial state is solved. Expressions are obtained for the density matrices of particles and antiparticles produced from a state with given number of initial particles and from a state described by an initial grand canonical ensemble.
Different methods of calculation of quantum corrections to the thermodynamical characteristics of... more Different methods of calculation of quantum corrections to the thermodynamical characteristics of a black hole are discussed and compared. The relation between on-shell and off-shell approaches is established. The off-shell methods are used to explicitly demonstrate that the thermodynamical entropy S T D of a black hole, defined by the first thermodynamical law, differs from the statistical-mechanical entropy S SM , determined as S SM = −Tr(ρ H lnρ H ) for the density matrixρ H of a black hole. It is shown that the observable thermodynamical black hole entropy can be presented in the form S T D = πr 2 + + S SM − S SM Rindler . Herer + is the radius of the horizon shifted because of the quantum backreaction effect, and S SM Rindler is the statistical-mechanical entropy calculated in the Rindler space.
A solution describing the configuration of a uniformly accelerated string in a flat D-dimensional... more A solution describing the configuration of a uniformly accelerated string in a flat D-dimensional space-time is found. It is shown that for a given size of the string there exists a critical acceleration. An instability arises when the acceleration reaches the critical value. This instabil ity is studied in detail. It is argued that the existence of a universal limiting acceleration must be a general property of string theory.
We study light curves and the spectral broadening of the radiation emitted during the finite inte... more We study light curves and the spectral broadening of the radiation emitted during the finite interval of time by a surface of a collapsing object. We study a simplified model of monochromatic radiations from a spherical surface which is assumed to be falling freely. We discuss the possible way how to infer the physical parameters, such as the mass and
Static spherically symmetric black holes are discussed in the framework of higher dimensional gra... more Static spherically symmetric black holes are discussed in the framework of higher dimensional gravity with quadratic in curvature terms. Such terms naturally arise as a result of quantum corrections induced by quantum fields propagating in the gravitational background. We focus our attention on the correction of the form C 2 ¼ C C. The Gauss-Bonnet equation in four-dimensional spacetime enables one to reduce this term in the action to the terms quadratic in the Ricci tensor and scalar curvature. As a result the Schwarzschild solution which is Ricci flat will be also a solution of the theory with the Weyl scalar C 2 correction. An important new feature of the spaces with dimension D > 4 is that in the presence of the Weyl curvature-squared term a necessary solution differs from the corresponding ''classical'' vacuum Tangherlini metric. This difference is related to the presence of secondary or induced hair. We explore how the Tangherlini solution is modified by ''quantum corrections,'' assuming that the gravitational radius r 0 is much larger than the scale of the quantum corrections. We also demonstrated that finding a general solution beyond the perturbation method can be reduced to solving a single third order ordinary differential equation (master equation).
We consider the action principle to derive the classical, nonrelativistic motion of a self-intera... more We consider the action principle to derive the classical, nonrelativistic motion of a self-interacting particle in a 4D Lorentzian spacetime containing a wormhole and which allows the existence of closed time-like curves. For the case of a “hard-sphere” self-interaction potential we show that the only possible trajectories (for a particle with fixed initial and final positions and which traverses the wormhole once) minimizing the classical action are those which are globally self-consistent, and that the “principle of self-consistency” (originally introduced by Novikov) is thus a natural consequence of the “principle of minimal action.”
Journal of Cosmology and Astroparticle Physics, 2014
We consider weakly magnetized non-rotating black holes. In the presence of a regular magnetic fie... more We consider weakly magnetized non-rotating black holes. In the presence of a regular magnetic field the motion of charged particles in the vicinity of a black hole is modified. As a result, the position of the innermost stable circular orbit (ISCO) becomes closer to the horizon. When the Lorentz force is repulsive (directed from the black hole) the ISCO radius can reach the gravitational radius. In the process of accretion charged particles (ions) of the accreting matter can be accumulated near their ISCO, while neutral particles fall down to the black hole after they reach 6M radius. The sharp spectral line Fe Kα, emitted by iron ions at such orbits, is broadened when the emission is registered by a distant observer. In this paper we study this broadening effect and discuss how one can extract information concerning the strength of the magnetic field from the observed spectrum.
One of the methods of study of black holes in astrophysics is based on broadening of the spectrum... more One of the methods of study of black holes in astrophysics is based on broadening of the spectrum of radiation of ionized Iron atoms. The line Kα associated with Iron emission at 6.4 keV is very narrow. If such an ion is revolving around a black hole, this line is effectively broadened as a result of the Doppler and gravitational redshift effects. The profile of the broaden spectrum contains information about the gravitational field of the black hole. In the presence of a regular magnetic field in the vicinity of a black holes the characteristics of the motion of charged ions are modified. In particular, their innermost stable circular orbits become closer to the horizon. The purpose of this work is to study how this effect modifies the spectrum broadening of lines emitted by such an ion. Our final goal is to analyze whether the change of the spectrum profiles can give us information about the magnetic field in the black hole vicinity.
Physical review D: Particles and fields, Jan 15, 1989
The first part of the paper formulates general conditions (independent of a particular gaugetheor... more The first part of the paper formulates general conditions (independent of a particular gaugetheoretic model) under which a cylindrical distribution of matter can be joined to a vacuum exterior with a conical geometry and exhibits the relation between angular deficit and internal structure. To bring out the relation to gravitational mass, the second part is devoted to a detailed study of solutions of the initial-value problem for circular loops of string at a moment of time symmetry.
The general problem of finding the density matrices of particles and antiparticles produced by an... more The general problem of finding the density matrices of particles and antiparticles produced by an external electromagnetic field fron an arbitrary initial state is solved. Expressions are obtained for the density matrices of particles and antiparticles produced from a state with given number of initial particles and from a state described by an initial grand canonical ensemble.
Different methods of calculation of quantum corrections to the thermodynamical characteristics of... more Different methods of calculation of quantum corrections to the thermodynamical characteristics of a black hole are discussed and compared. The relation between on-shell and off-shell approaches is established. The off-shell methods are used to explicitly demonstrate that the thermodynamical entropy S T D of a black hole, defined by the first thermodynamical law, differs from the statistical-mechanical entropy S SM , determined as S SM = −Tr(ρ H lnρ H ) for the density matrixρ H of a black hole. It is shown that the observable thermodynamical black hole entropy can be presented in the form S T D = πr 2 + + S SM − S SM Rindler . Herer + is the radius of the horizon shifted because of the quantum backreaction effect, and S SM Rindler is the statistical-mechanical entropy calculated in the Rindler space.
A solution describing the configuration of a uniformly accelerated string in a flat D-dimensional... more A solution describing the configuration of a uniformly accelerated string in a flat D-dimensional space-time is found. It is shown that for a given size of the string there exists a critical acceleration. An instability arises when the acceleration reaches the critical value. This instabil ity is studied in detail. It is argued that the existence of a universal limiting acceleration must be a general property of string theory.
We study light curves and the spectral broadening of the radiation emitted during the finite inte... more We study light curves and the spectral broadening of the radiation emitted during the finite interval of time by a surface of a collapsing object. We study a simplified model of monochromatic radiations from a spherical surface which is assumed to be falling freely. We discuss the possible way how to infer the physical parameters, such as the mass and
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Papers by Valeri Frolov