scholarly journals BLACK HOLES, ENTROPY BOUND AND CAUSALITY VIOLATION

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3584-3591 ◽  
Author(s):  
I. P. NEUPANE
Keyword(s):  
Black Hole ◽  
Classical Limit ◽  
Gauge Theories ◽  
Black Hole Entropy ◽  
Einstein Gravity ◽  
Entropy Density ◽  
Causality Violation ◽  
High Energies ◽  
Gravity Duality ◽  
Black Hole Solutions

The gauge theory - gravity duality has provided us a way of studying QCD at high energies or short distances from straightforward calculations in classical general relativity. Among numerous results obtained so far, one of the most striking is the universality of the ratio of the shear viscosity to the entropy density. For all gauge theories with Einstein gravity dual this ratio has been found to be η/s = 1/4π. In this note, we consider higher curvature-corrected black hole solutions for which η/s can be smaller than 1/4π, thus violating the conjecture bound. Here we shall argue that the Gauss-Bonnet gravity and (Riemann)2 gravity theories, in particular, provide concrete examples in which inconsistency of a theory, such as a violation of microcausality at short distances, and a classical limit on black hole entropy are correlated.

scholarly journals Causality of black holes in 4-dimensional Einstein–Gauss–Bonnet–Maxwell theory

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Xian-Hui Ge ◽  
Sang-Jin Sin
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Shear Viscosity ◽  
Upper Bound ◽  
Causal Structure ◽  
Density Ratio ◽  
Entropy Density ◽  
Coupling Constant ◽  
Maxwell Theory ◽  
Black Hole Solutions

Abstract We study charged black hole solutions in 4-dimensional (4D) Einstein–Gauss–Bonnet–Maxwell theory to the linearized perturbation level. We first compute the shear viscosity to entropy density ratio. We then demonstrate how bulk causal structure analysis imposes an upper bound on the Gauss–Bonnet coupling constant in the AdS space. Causality constrains the value of Gauss–Bonnet coupling constant $$\alpha _{GB}$$αGB to be bounded by $$\alpha _{GB}\le 0$$αGB≤0 as $$D\rightarrow 4$$D→4.

scholarly journals Discussion of a Possible Corrected Black Hole Entropy

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Miao He ◽  
Ziliang Wang ◽  
Chao Fang ◽  
Daoquan Sun ◽  
Jianbo Deng
Keyword(s):  
Black Hole ◽  
Electromagnetic Field ◽  
Black Hole Entropy ◽  
Einstein Gravity ◽  
Matter Field ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Corrected Entropy ◽  
Entropy Of Black Hole ◽  
Spherically Symmetric Solution

Einstein’s equation could be interpreted as the first law of thermodynamics near the spherically symmetric horizon. Through recalling the Einstein gravity with a more general static spherical symmetric metric, we find that the entropy would have a correction in Einstein gravity. By using this method, we investigate the Eddington-inspired Born-Infeld (EiBI) gravity. Without matter field, we can also derive the first law in EiBI gravity. With an electromagnetic field, as the field equations have a more general spherically symmetric solution in EiBI gravity, we find that correction of the entropy could be generalized to EiBI gravity. Furthermore, we point out that the Einstein gravity and EiBI gravity might be equivalent on the event horizon. At last, under EiBI gravity with the electromagnetic field, a specific corrected entropy of black hole is given.

scholarly journals Non-hermitian holography

2020 ◽  
Vol 9 (3) ◽  
Author(s):  
Daniel Arean ◽  
Karl Landsteiner ◽  
Ignacio Salazar Landea
Keyword(s):  
Phase Transition ◽  
Black Hole ◽  
Quantum Theory ◽  
Finite Temperature ◽  
Similarity Transformation ◽  
Zero Temperature ◽  
Gauge Gravity ◽  
Gravity Duality ◽  
Linear Involution ◽  
Black Hole Solutions

Quantum theory can be formulated with certain non-Hermitian Hamiltonians. An anti-linear involution, denoted by PT, is a symmetry of such Hamiltonians. In the PT-symmetric regime the non-Hermitian Hamiltonian is related to a Hermitian one by a Hermitian similarity transformation. We extend the concept of non-Hermitian quantum theory to gauge-gravity duality. Non-Hermiticity is introduced via boundary conditions in asymptotically AdS spacetimes. At zero temperature the PT phase transition is identified as the point at which the solutions cease to be real. Surprisingly at finite temperature real black hole solutions can be found well outside the quasi-Hermitian regime. These backgrounds are however unstable to fluctuations which establishes the persistence of the holographic dual of the PT phase transition at finite temperature.

scholarly journals An exploration of the black hole entropy in Gauss–Bonnet gravity via the Weyl tensor

2021 ◽  
pp. 2150193
Author(s):  
Taha A. Malik ◽  
Rafael Lopez-Mobilia
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Weyl Tensor ◽  
Black Hole Entropy ◽  
Entropy Density ◽  
Modified Theories Of Gravity ◽  
Bonnet Gravity ◽  
Gravitational Entropy ◽  
Theories Of Gravity ◽  
Almost All

Various proposals for gravitational entropy densities have been constructed from the Weyl tensor. In almost all cases, though, these studies have been restricted to general relativity, and little has been done in modified theories of gravity. However, in this paper, we investigate the simplest proposal for an entropy density constructed from the Weyl tensor in five-dimensional Gauss–Bonnet gravity and find that it fails to reproduce the expected entropy of a black hole.

scholarly journals Exact charged black hole solutions in D-dimensions in f(R) gravity

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Zi-Yu Tang ◽  
Bin Wang ◽  
Eleftherios Papantonopoulos
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
General Solution ◽  
Constant Curvature ◽  
Black Hole Solution ◽  
Einstein Gravity ◽  
Charged Black Hole ◽  
Spherically Symmetric ◽  
Spherically Symmetric Metric ◽  
Black Hole Solutions

AbstractWe consider Maxwell-f(R) gravity and obtain an exact charged black hole solution with dynamic curvature in D-dimensions. Considering a spherically symmetric metric ansatz and without specifying the form of f(R) we find a general black hole solution in D-dimensions. This general black hole solution can reduce to the Reissner–Nordström (RN) black hole in D-dimensions in Einstein gravity and to the known charged black hole solutions with constant curvature in f(R) gravity. Restricting the parameters of the general solution we get polynomial solutions which reveal novel properties when compared to RN black holes. Specifically we study the solution in $$(3+1)$$ ( 3 + 1 ) -dimensions in which the form of f(R) can be solved explicitly giving a dynamic curvature and compare it with the RN black hole. We also carry out a detailed study of its thermodynamics.

Slowly rotating black holes with nonlinear electrodynamics in five dimensions

2014 ◽  
Vol 23 (11) ◽  
pp. 1450095 ◽  
Author(s):  
S. H. Hendi ◽  
M. Sepehri Rad
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Einstein Gravity ◽  
Rotation Parameter ◽  
Nonlinear Electrodynamics ◽  
Five Dimensions ◽  
Angular Momenta ◽  
Static Black Hole ◽  
Rotating Black Holes ◽  
Black Hole Solutions

Employing linear order perturbation theory with the rotation parameter as the perturbative parameter, we obtain asymptotically AdS slowly rotating black hole solutions in the Einstein gravity with Born–Infeld (BI) type nonlinear electrodynamics (NED). We start from asymptotically AdS static black hole solutions coupled to BI type NED in five dimensions. Then, we consider the effect of adding a small amount of angular momenta to the seed solutions. Finally, we investigate the geometry and thermodynamic properties of the solutions.

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.

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 Review of lattice supersymmetry and gauge-gravity duality

2015 ◽  
Vol 30 (27) ◽  
pp. 1530054 ◽  
Author(s):  
Anosh Joseph
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Mechanics ◽  
Gauge Theory ◽  
Gauge Theories ◽  
Strongly Coupled ◽  
The Status ◽  
Gauge Gravity ◽  
Gravity Duality ◽  
Insight Into

We review the status of recent investigations on validating the gauge-gravity duality conjecture through numerical simulations of strongly coupled maximally supersymmetric thermal gauge theories. In the simplest setting, the gauge-gravity duality connects systems of D0-branes and black hole geometries at finite temperature to maximally supersymmetric gauged quantum mechanics at the same temperature. Recent simulations show that nonperturbative gauge theory results give excellent agreement with the quantum gravity predictions, thus proving strong evidence for the validity of the duality conjecture and more insight into quantum black holes and gravity.

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