arXiv subjects

Mikhail Z. Iofa

Publications and source records attributed to Mikhail Z. Iofa.

24 records · Page 2Linked to original sources

arXiv2002

String-Loop Corrected Magnetic Black Holes

We discuss the form of the string-loop-corrected effective action obtained by compactification of the heterotic string theory on the manifold $K3\times T^2$ or on its orbifold limit and the loop-corrected magnetic black hole solutions of the equations of motion. Effective 4D theory has N=2 local supersymmetry. Using the string-loop-corrected prepotential of the N=2 supersymmetric theory, which receives corrections only from the string world sheets of torus topology, we calculate the loop corrections to the tree-level gauge couplings and solve the loop-corrected equations of motion. At the string-tree level, the effective gauge couplings decrease at small distances from the origin, and in this region string-loop corrections to the gauge couplings become important. A possibility of smearing the singularity of the tree-level supersymmetric solution with partially broken supersymmetry by quantum corrections is discussed.

hep-th↗

arXiv2002

N=2 Supersymmetry and String-Loop Corrected Magnetic Black Holes

We study string-loop corrections to magnetic black hole. Four-dimensional theory is obtained by compactification of the heterotic string theory on the manifold $K3\times T^2$ or on a suitable orbifold yielding N=1 supersymmetry in 6D. The resulting 4D theory has N=2 local supersymmetry. Prepotential of this theory receives only one-string-loop correction. The tree-level gauge couplings are proportional to the inverse effective string coupling and decrease at small distances from the center of magnetic black hole, so that loop corrections to the gauge couplings are important in this region. We solve the system of spinor Killing equations (conditions for the supersymmetry variations of the fermions to vanish) and Maxwell equations. At the string-tree level, we reproduce the magnetic black hole solution which can be also obtained by solving the system of the Einstein-Maxwell equations and the equations of motion for the moduli. String-loop corrections to the tree-level solution are calculated in the first order in string coupling. The resulting corrections to the metric and dilaton are large at small distances from the center of the black hole. Possible smearing of the singularity at the origin by quantum corrections is discussed.

hep-th↗

arXiv1999

String-Loop Corrections Versus Non-Extremality

We discuss a magnetic black-hole solution to the equations of motion of the string-loop-corrected effective action. At the string-tree level, this solution is the extremal magnetic black hole described by the "chiral null model." In the extremal case, the string-loop correction is constant, and this fact is used to analytically solve the loop-corrected equations of motion. In distinction to the tree-level solution, the resulting loop-corrected solution has the horizon at a finite distance from the origin; its location is a function of the loop correction. The loop-corrected configuration is compared with a string-tree-level non-extremal magnetic black hole solution which also has the horizon at a finite distance from the origin. We find that for an appropriate choice of the free parameters of solutions, the loop-corrected magnetic black hole can be approximated by a tree-level non-extremal solution. We compare the thermodynamic properties of the loop-corrrected and non-extremal solutions.

hep-th↗

arXiv1998

Statistical Entropy of Magnetic Black Holes from Near--Horizon Geometry

Four-dimensional magnetic black holes including dilaton and abelian gauge fields which are solutions of supergravity can also be obtained by dimensional reduction of the Einstein-Maxwell gravity in five dimensions. In the extremal case the five-dimensional solutions have horizon and their near-horizon geometry is $AdS_3\times S^2 $. In the non-extremal case the near-horizon geometry is shown to be the product of the three-dimensional Bañados-Teitelboim-Zanelli black hole and $S^2$. This allows to perform microscopic counting of statistical entropy of magnetic black holes. Exact agreement with the geometric entropy is found. The microstates responsible for statistical entropy are located in the near-horizon region.

hep-th↗

arXiv1998

Statistical Entropy of Calabi-Yau Black Holes

We computed the statistical entropy of nonextremal 4D and extremal 5D Calabi-Yau black holes and found exact agreement with the Bekenstein-Hawking entropy. The computation is based on the fact that the near-horizon geometry of equivalent representations contains as a factor the Bañados-Teitelboim-Zanelli black hole and on subsequent use of Strominger's proposal generalizing the statistical count of microstates of the BTZ black hole due to Carlip.

hep-th↗

arXiv1997

On Genus-One-Corrected Extremal Black Holes and the Correspondence Principle

We discuss charged black-hole solutions to the equations of motion of the string-loop-corrected effective action. At the string-tree level, these solutions provide backgrounds for the "chiral null model". The effective action contains gravity, dilaton and moduli fields. Analytic solutions of the one-loop-corrected equations of motion are presented for the extremal magnetic and dyonic black holes. Using the fact that in magnetic solution the loop-corrected dilaton is non-singular at the origin, we apply the correspondence principle to show that the entropy of the loop-corrected magnetic black hole can be interpreted as the microscopic entropy of the D-brane system.

hep-th↗