scholarly journals Charged spherically symmetric Taub–NUT black hole solutions in $f(R)$ gravity

2020 ◽  
Vol 2020 (4) ◽  
Author(s):  
G G L Nashed ◽  
Kazuharu Bamba
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Free Energy ◽  
Black Hole Solution ◽  
Energy Conditions ◽  
Thermodynamic Quantities ◽  
Spherically Symmetric ◽  
Dimensional Parameter ◽  
Charged Black Holes ◽  
Black Hole Solutions

Abstract $f(R)$ theory is a modification of Einstein’s general relativity which has provided many interesting results in cosmology and astrophysics. To derive a black hole solution in this theory is difficult due to the fact that it contains fourth-order differential equations. In this study, we use the first reliable deviation from general relativity which is given by the quadratic form of $f(R)=R+\beta R^2$, where $\beta$ is a dimensional parameter. We calculate the energy conditions of charged black holes and show that they are all satisfied for the Taub–NUT spacetime. Finally, we study some thermodynamic quantities such as entropy, temperature, specific heat, and Gibbs free energy. The calculations of heat capacity and free energy show that the charged Taub–NUT black hole has positive values, which means that it has thermal stability.

scholarly journals Constructing black hole solutions in supergravity theories

2019 ◽  
Vol 34 (35) ◽  
pp. 1930017 ◽  
Author(s):  
Antonio Gallerati
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Supergravity Models ◽  
Detailed Analysis ◽  
Black Hole Solution ◽  
Explicit Construction ◽  
General Introduction ◽  
Supersymmetric Theories ◽  
Black Hole Solutions

We perform a detailed analysis of black hole solutions in supergravity models. After a general introduction on black holes in general relativity and supersymmetric theories, we provide a detailed description of ungauged extended supergravities and their dualities. Therefore, we analyze the general form of black hole configurations for these models, their near-horizon behavior and characteristic of the solution. An explicit construction of a black hole solution with its physical implications is given for the STU-model. The second part of this review is dedicated to gauged supergravity theories. We describe a step-by-step gauging procedure involving the embedding tensor formalism to be used to obtain a gauged model starting from an ungauged one. Finally, we analyze general black hole solutions in gauged models, providing an explicit example for the [Formula: see text], [Formula: see text] case. A brief review on special geometry is also provided, with explicit results and relations for supersymmetric black hole solutions.

scholarly journals On the Energy of a Non-Singular Black Hole Solution Satisfying the Weak Energy Condition

Universe ◽  
2020 ◽  
Vol 6 (10) ◽  
pp. 169
Author(s):  
Irina Radinschi ◽  
Theophanes Grammenos ◽  
Farook Rahaman ◽  
Marius-Mihai Cazacu ◽  
Andromahi Spanou ◽  
...  
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Energy Distribution ◽  
Black Hole Solution ◽  
Energy Condition ◽  
Weak Energy Condition ◽  
Radial Coordinate ◽  
Spherically Symmetric ◽  
Comparison Of The Results ◽  
Two Parameters

The energy-momentum localization for a new four-dimensional and spherically symmetric, charged black hole solution that through a coupling of general relativity with non-linear electrodynamics is everywhere non-singular while it satisfies the weak energy condition, is investigated. The Einstein and Møller energy-momentum complexes have been employed in order to calculate the energy distribution and the momenta for the aforesaid solution. It is found that the energy distribution depends explicitly on the mass and the charge of the black hole, on two parameters arising from the space-time geometry considered, and on the radial coordinate. Further, in both prescriptions all the momenta vanish. In addition, a comparison of the results obtained by the two energy-momentum complexes is made, whereby some limiting and particular cases are pointed out.

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.

Spherically symmetric black hole solution in mimetic gravity and anti-evaporation

2018 ◽  
Vol 15 (09) ◽  
pp. 1850154 ◽  
Author(s):  
G. G. L. Nashed
Keyword(s):  
Black Hole ◽  
Black Hole Solution ◽  
Spherically Symmetric ◽  
Mimetic Theory ◽  
Event Horizons ◽  
Flat Spacetime ◽  
Symmetric Black Hole ◽  
The Stability ◽  
Mimetic Gravity ◽  
Black Hole Solutions

In this paper, we study the mimetic theory and derive a new spherically symmetric black hole solution. The asymptotic behavior of this solution behaves as a flat spacetime. This black hole is characterized by the fact that it has different components of [Formula: see text] and [Formula: see text]. Nevertheless, both of these components have a coinciding Killing and event horizons. Furthermore, this black hole has curvature singularities which are stronger than those of the known black hole solutions in general relativity. This feature can be shown by calculating some invariants of curvature. We study the stability of the perturbation and the related anti-evaporation of the Nariai spacetime.

scholarly journals Regular charged black holes, quasilocal energy and energy conditions

2016 ◽  
Vol 25 (06) ◽  
pp. 1650072 ◽  
Author(s):  
Leonardo Balart ◽  
Francisco Peña
Keyword(s):  
Black Hole ◽  
Energy Condition ◽  
Nonlinear Electrodynamics ◽  
Energy Conditions ◽  
Field Energy ◽  
Regular Black Hole ◽  
Charged Black Holes ◽  
Relationship Of ◽  
The Relationship ◽  
Black Hole Solutions

We revisit the relationship of inequality between the gravitational field energy and the Komar charge, both quantities evaluated at the event horizon, for static and spherically symmetric regular black hole solutions obtained with nonlinear electrodynamics. We found a way to characterize these regular black hole solutions by the energy conditions that they satisfy. In particular, we show the relation between the direction of the inequality and the energy condition that satisfies the regular black hole solutions.

scholarly journals Higher Dimensional Rotating Black Hole Solutions in Quadratic f(R) Gravitational Theory and the Conserved Quantities

Entropy ◽  
2021 ◽  
Vol 23 (3) ◽  
pp. 358
Author(s):  
Gamal G. L. Nashed ◽  
Kazuharu Bamba
Keyword(s):  
Black Hole ◽  
Gravitational Theory ◽  
Thermodynamic Quantities ◽  
Conserved Quantities ◽  
Dimensional Parameter ◽  
Dimensional Spacetime ◽  
Higher Dimensional ◽  
Physics Of Black Holes ◽  
The Stability ◽  
Black Hole Solutions

We explore the quadratic form of the f(R)=R+bR2 gravitational theory to derive rotating N-dimensions black hole solutions with ai,i≥1 rotation parameters. Here, R is the Ricci scalar and b is the dimensional parameter. We assumed that the N-dimensional spacetime is static and it has flat horizons with a zero curvature boundary. We investigated the physics of black holes by calculating the relations of physical quantities such as the horizon radius and mass. We also demonstrate that, in the four-dimensional case, the higher-order curvature does not contribute to the black hole, i.e., black hole does not depend on the dimensional parameter b, whereas, in the case of N>4, it depends on parameter b, owing to the contribution of the correction R2 term. We analyze the conserved quantities, energy, and angular-momentum, of black hole solutions by applying the relocalization method. Additionally, we calculate the thermodynamic quantities, such as temperature and entropy, and examine the stability of black hole solutions locally and show that they have thermodynamic stability. Moreover, the calculations of entropy put a constraint on the parameter b to be b<116Λ to obtain a positive entropy.

scholarly journals Black hole solution in the framework of arctan-electrodynamics

2017 ◽  
Vol 26 (08) ◽  
pp. 1750075 ◽  
Author(s):  
S. I. Kruglov
Keyword(s):  
Black Hole ◽  
Black Hole Solution ◽  
De Sitter ◽  
Dimensional Parameter ◽  
Regular Black Hole ◽  
Charged Black Holes ◽  
Classical Stability ◽  
Electric And Magnetic Fields ◽  
Magnetic Mass ◽  
Metric Function

An arctan-electrodynamics coupled with the gravitational field is investigated. We obtain the regular black hole solution that at [Formula: see text] gives corrections to the Reissner–Nordström solution. The corrections to Coulomb’s law at [Formula: see text] are found. We evaluate the mass of the black hole that is a function of the dimensional parameter [Formula: see text] introduced in the model. The magnetically charged black hole was investigated and we have obtained the magnetic mass of the black hole and the metric function at [Formula: see text]. The regular black hole solution is obtained at [Formula: see text] with the de Sitter core. We show that there is no singularity of the Ricci scalar for electrically and magnetically charged black holes. Restrictions on the electric and magnetic fields are found that follow from the requirement of the absence of superluminal sound speed and the requirement of a classical stability.

scholarly journals A Smarr formula for charged black holes in nonlinear electrodynamics

2017 ◽  
Vol 32 (39) ◽  
pp. 1750219 ◽  
Author(s):  
Leonardo Balart ◽  
Sharmanthie Fernando
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
General Formula ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Nonlinear Electrodynamics ◽  
Spherically Symmetric ◽  
Charged Black Holes ◽  
Electrically Charged ◽  
Black Hole Solutions

It is well known that the Smarr formula does not hold for black holes in nonlinear electrodynamics. The main reason for this is the fact that the trace of the energy–momentum tensor for nonlinear electrodynamics does not vanish as it is for Maxwell’s electrodynamics. Starting from the Komar integral, we derived a new Smarr-type formula for spherically symmetric static electrically charged black hole solutions in nonlinear electrodynamics. We show that this general formula is in agreement with some that are obtained for black hole solutions with nonlinear electrodynamics.

scholarly journals New supersymmetric black holes in four-dimensional N = 2 supergravity

2016 ◽  
Vol 31 (16) ◽  
pp. 1650100
Author(s):  
Taniya Mandal ◽  
Prasanta K. Tripathy
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Harmonic Functions ◽  
Black Hole Solution ◽  
Spherically Symmetric ◽  
Algebraic Equations ◽  
Supergravity Theory ◽  
Flow Equations ◽  
Holomorphic Sections ◽  
Black Hole Solutions

In this paper, we consider the four-dimensional N = 2 supergravity theory arising from the compactification of type IIA string theory on a Calabi–Yau manifold. We analyze the supersymmetric flow equations for static, spherically symmetric, single-centered black holes. These flow equations are solved by a set of algebraic equations involving the holomorphic sections and harmonic functions. We examine black hole configurations with D0–D4–D6 charge for which the most general solution of these algebraic equations are considered. Though the black hole solution is unique for a given value of the charges, we find new phases of the black hole solutions upon varying them.

Solar System Tests in Einstein- Æther gravity

2021 ◽  
Author(s):  
Tuhina Manna ◽  
Bidisha Samanta ◽  
Amna Ali ◽  
Farook Rahaman
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Time Delay ◽  
Solar System ◽  
Coupling Constants ◽  
Spherically Symmetric ◽  
Tests Of General Relativity ◽  
Range Of Values ◽  
Vast Range ◽  
Black Hole Solutions

In the current paper we analyze the three classical tests of general relativity, viz. the precession of perihelion, deflection of light and time delay in Einstein Æther gravity. Einstein Æther gravity has two static, spherically symmetric, charged solutions of black hole solutions corresponding to different constraints on its coupling constants c<sub>14</sub>, and c<sub>123</sub>. We investigate the aforementioned tests for both these solutions, graphically and analytically. We also tabulate our results and discuss the outcome which is promising. We evaluate the results, when the coupling constants are varied over a vast range of values, both within the constraints set by the recent observational data, and also beyond, for a comparative study.

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