scholarly journals MULTI-BLACK HOLES AND INSTANTONS IN EFFECTIVE STRING THEORY

1998 ◽  
Vol 07 (01) ◽  
pp. 73-80
Author(s):  
S. DEMELIO ◽  
S. MIGNEMI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
String Theory ◽  
Higher Dimensions ◽  
Field Equations ◽  
Charged Black Holes ◽  
Effective String Theory ◽  
Black Hole Solutions

The effective four-dimensional action for string theory contains non-minimal couplings of the dilaton and the moduli arising from the compactification of higher dimensions. We show that the resulting field equations admit multi-black hole solutions. The Euclidean continuation of these solutions can be interpreted as an instanton mediating the splitting and recombination of the throat of extremal magnetically charged black holes.

scholarly journals ENTROPY OF EXTREMAL DYONIC BLACK HOLES

1996 ◽  
Vol 11 (37) ◽  
pp. 2933-2939 ◽  
Author(s):  
A. GHOSH ◽  
P. MITRA
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
String Theory ◽  
Extremal Black Hole ◽  
Classical Action ◽  
Charged Black Holes ◽  
Thermodynamic Entropy ◽  
Black Hole Solutions

For extremal charged black holes, the thermodynamic entropy is proportional to the mass or charges but not proportional to the area. This is demonstrated here for dyonic extremal black hole solutions of string theory. It is pointed out that these solutions have zero classical action although the area is nonzero. By combining the general form of the entropy allowed by thermodynamics with recent observations in the literature it is possible to fix the entropy almost completely.

scholarly journals NONEXTREME BLACK HOLES FROM INTERSECTING M-BRANES

1998 ◽  
Vol 13 (08) ◽  
pp. 1305-1328 ◽  
Author(s):  
NOBUYOSHI OHTA ◽  
TAKASHI SHIMIZU
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Higher Dimensions ◽  
Symmetric Case ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Deformation Parameters ◽  
Special Cases ◽  
Two Parameter ◽  
Black Hole Solutions

We investigate the possibility of extending nonextreme black hole solutions made of intersecting M-branes to those with two nonextreme deformation parameters, similar to Reissner–Nordstrøm solutions. General analysis of possible solutions is carried out to reduce the problem of solving field equations to a simple algebraic one for static spherically-symmetric case in D dimensions. The results are used to show that the extension to two-parameter solutions is possible for D= 4,5 dimensions but not for higher dimensions, and that the area of horizon always vanishes in the extreme limit for black hole solutions for D≥6 except for two very special cases which are identified. Various solutions are also summarized.

scholarly journals Thermodynamics and reentrant phase transition for logarithmic nonlinear charged black holes in massive gravity

2020 ◽  
Vol 29 (12) ◽  
pp. 2050081
Author(s):  
S. Rajaee Chaloshtary ◽  
M. Kord Zangeneh ◽  
S. Hajkhalili ◽  
A. Sheykhi ◽  
S. M. Zebarjad
Keyword(s):  
Phase Transition ◽  
Black Holes ◽  
Black Hole ◽  
Quantum Effect ◽  
Massive Gravity ◽  
Nonlinear Electrodynamics ◽  
Model Parameters ◽  
Thermodynamic Quantities ◽  
Field Equations ◽  
Black Hole Solutions

We investigate a new class of [Formula: see text]-dimensional topological black hole solutions in the context of massive gravity and in the presence of logarithmic nonlinear electrodynamics. Exploring higher-dimensional solutions in massive gravity coupled to nonlinear electrodynamics is motivated by holographic hypothesis as well as string theory. We first construct exact solutions of the field equations and then explore the behavior of the metric functions for different values of the model parameters. We observe that our black holes admit the multi-horizons caused by a quantum effect called anti-evaporation. Next, by calculating the conserved and thermodynamic quantities, we obtain a generalized Smarr formula. We find that the first law of black holes thermodynamics is satisfied on the black hole horizon. We study thermal stability of the obtained solutions in both canonical and grand canonical ensembles. We reveal that depending on the model parameters, our solutions exhibit a rich variety of phase structures. Finally, we explore, for the first time without extending thermodynamics phase space, the critical behavior and reentrant phase transition for black hole solutions in massive gravity theory. We realize that there is a zeroth-order phase transition for a specified range of charge value and the system experiences a large/small/large reentrant phase transition due to the presence of nonlinear electrodynamics.

scholarly journals DUALITIES, COMPOSITENESS AND SPACE–TIME STRUCTURE OF 4D EXTREME STRINGY BLACK HOLES

1999 ◽  
Vol 14 (07) ◽  
pp. 1015-1034 ◽  
Author(s):  
MARIANO CADONI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
String Theory ◽  
Bound States ◽  
Bound State ◽  
Space Time ◽  
Naked Singularities ◽  
Heterotic String Theory ◽  
Space Time Structure ◽  
Black Hole Solutions

We study the BPS black hole solutions of the (truncated) action for heterotic string theory compactified on a six-torus. The O (3,Z) duality symmetry of the theory, together with the bound state interpretation of extreme black holes, is used to generate the whole spectrum of the solutions. The corresponding space–time structures, written in terms of the string metric, are analyzed in detail. In particular, we show that only the elementary solutions present naked singularities. The bound states have either null singularities (electric solutions) or are regular (magnetic or dyonic solutions) with near-horizon geometries given by the product of two 2d spaces of constant curvature. The behavior of some of these solutions as supersymmetric attractors is discussed. We also show that our approach is very useful to understand some of the puzzling features of charged black hole solutions in string theory.

scholarly journals S-DUALITY AND THE ENTROPY OF BLACK HOLES IN HETEROTIC STRING THEORY

1996 ◽  
Vol 11 (39n40) ◽  
pp. 3103-3111 ◽  
Author(s):  
AMIT GHOSH ◽  
JNANADEVA MAHARANA
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Partition Function ◽  
Heterotic String ◽  
Heterotic String Theory ◽  
Charged Black Holes ◽  
Duality Transformations ◽  
Extremal Limit ◽  
Electrically Charged ◽  
Black Hole Solutions

Four-dimensional heterotic string effective action is known to admit non-rotating electrically and magnetically charged black hole solutions. The partition function and entropy is computed for electrically charged black holes and is vanishing in some extremal limit. For the magnetically charged black holes the entropy is also argued to be vanishing in the same extremal limit when these black hole solutions are related by S-duality transformations.

scholarly journals Dirac quasinormal modes of power-Maxwell charged black holes in Rastall gravity

2020 ◽  
Vol 35 (23) ◽  
pp. 2050193
Author(s):  
Cai-Ying Shao ◽  
Yu Hu ◽  
Yu-Jie Tan ◽  
Cheng-Gang Shao ◽  
Kai Lin ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Matrix Method ◽  
Quasinormal Modes ◽  
Einstein Gravity ◽  
Late Time ◽  
Charged Black Holes ◽  
The Matrix ◽  
Black Hole Solutions ◽  
Extremal Black Holes

In this paper, we study the quasinormal modes of the massless Dirac field for charged black holes in Rastall gravity. The spherically symmetric black hole solutions in question are characterized by the presence of a power-Maxwell field, surrounded by the quintessence fluid. The calculations are carried out by employing the WKB approximations up to the 13th-order, as well as the matrix method. The temporal evolution of the quasinormal modes is investigated by using the finite difference method. Through numerical simulations, the properties of the quasinormal frequencies are analyzed, including those for the extremal black holes. Among others, we explore the case of a second type of extremal black holes regarding the Nariai solution, where the cosmical and event horizon coincide. The results obtained by the WKB approaches are found to be mostly consistent with those by the matrix method. It is observed that the magnitudes of both real and imaginary parts of the quasinormal frequencies increase with increasing [Formula: see text], the spin–orbit quantum number. Also, the roles of the parameters [Formula: see text] and [Formula: see text], associated with the electric charge and the equation of state of the quintessence field, respectively, are investigated regarding their effects on the quasinormal frequencies. The magnitude of the electric charge is found to sensitively affect the time scale of the first stage of quasinormal oscillations, after which the temporal oscillations become stabilized. It is demonstrated that the black hole solutions for Rastall gravity in asymptotically flat spacetimes are equivalent to those in Einstein gravity, featured by different asymptotical spacetime properties. As one of its possible consequences, we also investigate the behavior of the late-time tails of quasinormal models in the present model. It is found that the asymptotical behavior of the late-time tails of quasinormal modes in Rastall theory is governed by the asymptotical properties of the spacetimes of their counterparts in Einstein gravity.

scholarly journals THE CARDY–VERLINDE FORMULA AND ASYMPTOTICALLY FLAT CHARGED BLACK HOLES

2001 ◽  
Vol 16 (19) ◽  
pp. 1263-1268 ◽  
Author(s):  
DONAM YOUM
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Casimir Effect ◽  
Higher Dimensions ◽  
Thermodynamic Quantities ◽  
Two Dimensional ◽  
Temperature Relation ◽  
Asymptotically Flat ◽  
Charged Black Holes ◽  
Verlinde Formula

We show that the modified Cardy–Verlinde formula without the Casimir effect term is satisfied by asymptotically flat charged black holes in arbitrary dimensions. Thermodynamic quantities of the charged black holes are shown to satisfy the energy-temperature relation of a two-dimensional CFT, which supports the claim in our previous work (Phys. Rev.D61, 044013, hep-th/9910244) that thermodynamics of charged black holes in higher dimensions can be effectively described by two-dimensional theories. We also check the Cardy formula for the two-dimensional black hole compactified from a dilatonic charged black hole in higher dimensions.

scholarly journals ON ATTRACTOR FLOW AND SMALL BLACK HOLES

2011 ◽  
Vol 26 (13) ◽  
pp. 967-974 ◽  
Author(s):  
SANJAY SIWACH ◽  
BHUPENDRA NATH TIWARI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
String Theory ◽  
Fixed Points ◽  
Entropy Function ◽  
Stability Conditions ◽  
Heterotic String Theory ◽  
The Stability ◽  
Horizon Geometry ◽  
Black Hole Solutions

We study the attractor flow and near horizon geometry of two-charge small black holes in heterotic string theory. The Hessian of Sen's entropy function with respect to the moduli fields has standard attractor properties and shows the interesting factorization at the attractor fixed points. We notice that the stability conditions are preserved under arbitrary α′-corrections to the black hole solutions.

Charged black holes in the infinite derivative theory of gravity

2021 ◽  
Author(s):  
Yong Xiao ◽  
Longting Zhang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Electromagnetic Field ◽  
Electrostatic Potential ◽  
Einstein Gravity ◽  
First Law Of Thermodynamics ◽  
Charged Black Holes ◽  
Theory Of Gravity ◽  
Infinite Derivative ◽  
Black Hole Solutions

Abstract The infinite derivative theory of gravity is a generalization of Einstein gravity with many interesting properties, but the black hole solutions in this theory are still not fully understood. In the paper, we concentrate on studying the charged black holes in such a theory. Adding the electromagnetic field part to the effective action, we show how the black hole solutions around the Reissner-Nordstr{\"o}m metric can be solved perturbatively and iteratively. We further calculate the corresponding temperature, entropy and electrostatic potential of the black holes and verify the first law of thermodynamics.

scholarly journals Charged black holes in effective string theory

1993 ◽  
Vol 47 (12) ◽  
pp. 5259-5269 ◽  
Author(s):  
S. Mignemi ◽  
N. R. Stewart
Keyword(s):  
Black Holes ◽  
String Theory ◽  
Charged Black Holes ◽  
Effective String Theory
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