scholarly journals Gravitational Decoupling in Higher Order Theories

Symmetry ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1598
Author(s):  
Joseph Sultana
Keyword(s):  
Black Hole ◽  
Black Hole Solution ◽  
Scalar Fields ◽  
Higher Order ◽  
Vacuum Field ◽  
Field Equations ◽  
Simple Method ◽  
Seed Solution ◽  
Homotopy Analysis ◽  
Weyl Scalar

Gravitational decoupling via the Minimal Geometric Deformation (MGD) approach has been used extensively in General Relativity (GR), mainly as a simple method for generating exact anisotropic solutions from perfect fluid seed solutions. Recently this method has also been used to generate exact spherically symmetric solutions of the Einstein-scalar system from the Schwarzschild vacuum metric. This was then used to investigate the effect of scalar fields on the Schwarzschild black hole solution. We show that this method can be extended to higher order theories. In particular, we consider fourth order Einstein–Weyl gravity, and in this case by using the Schwarzschild metric as a seed solution to the associated vacuum field equations, we apply the MGD method to generate a solution to the Einstein–Weyl scalar theory representing a hairy black hole solution. This solution is expressed in terms of a series using the Homotopy Analysis Method (HAM).

scholarly journals Black hole solutions in Rastall theory

2017 ◽  
Vol 95 (12) ◽  
pp. 1253-1256 ◽  
Author(s):  
Y. Heydarzade ◽  
H. Moradpour ◽  
F. Darabi
Keyword(s):  
Black Hole ◽  
General Solution ◽  
Symmetric Space ◽  
Cosmological Constant ◽  
Black Hole Solution ◽  
Ad Hoc ◽  
Vacuum Field ◽  
De Sitter ◽  
Field Equations ◽  
Black Hole Solutions

The Reissner–Nordström black hole solution in a generic cosmological constant background in the context of Rastall gravity is obtained. It is shown that the cosmological constant arises naturally from the consistency of the non-vacuum field equations of the Rastall theory for a spherical symmetric space–time, rather than its ad hoc introduction in the usual Einstein and Einstein–Maxwell field equations. The usual Reissner–Nordström, Schwarzschild, and Schwarzschild – (anti-)de Sitter black hole solutions in the framework of this theory are also addressed as the special independent subclasses of the obtained general solution.

General form of the analytic function f(T) in diverse dimension for a static planar spacetime

2019 ◽  
Vol 28 (12) ◽  
pp. 1950158 ◽  
Author(s):  
Gamal Nashed
Keyword(s):  
Black Hole ◽  
Analytic Function ◽  
Black Hole Solution ◽  
Static Solution ◽  
Gravitational Theory ◽  
Interesting Property ◽  
Constant Function ◽  
Field Equations ◽  
Adm Mass ◽  
Laws Of Thermodynamics

We derive an exact static solution in diverse dimension, without any constraints, to the field equations of [Formula: see text] gravitational theory using a planar spacetime with two unknown functions, i.e. [Formula: see text] and [Formula: see text]. The black hole solution is characterized by two constants, [Formula: see text] and [Formula: see text], one is related to the mass of the black hole, [Formula: see text], and the other is responsible to make the solution deviate from the teleparallel equivalent of general relativity (TEGR). We show that the analytic function [Formula: see text] depends on the constant [Formula: see text] and becomes constant function when [Formula: see text] which corresponds to the TEGR case. The interesting property of this solution is the fact that it makes the singularity of the Kretschmann invariant much softer than the TEGR case. We calculate the energy of this black hole and show that it is equivalent to ADM mass. Applying a coordinate transformation, we derive a rotating black hole with nontrivial values of the torsion scalar and [Formula: see text]. Finally, we examine the physical properties of this black hole solution using the laws of thermodynamics and show that it has thermodynamical stability.

scholarly journals Cosmological isotropic matter–energy generalizations of Schwarzschild and Kerr metrics

2016 ◽  
Vol 25 (10) ◽  
pp. 1650088
Author(s):  
Metin Arik ◽  
Yorgo Senikoglu
Keyword(s):  
Black Hole ◽  
Dark Energy ◽  
Black Hole Solution ◽  
State Parameter ◽  
Time Dependent ◽  
Schwarzschild Black Hole ◽  
Field Equations ◽  
Rotating Black Hole ◽  
Special Solutions ◽  
Matter Energy

We present a time-dependent isotropic fluid solution around a Schwarzschild black hole. We offer the solutions and discuss the effects on the field equations and the horizon. We derive the energy density, pressure and the equation of state parameter. In the second part, we generalize the rotating black hole solution to an expanding universe. We derive from the proposed metric the special solutions of the field equations for the dust approximation and the dark energy solution. We show that the presence of a rotating black hole does not modify the scale factor [Formula: see text] law for dust, nor [Formula: see text] and [Formula: see text] for dark energy.

scholarly journals BLACK-HOLE SOLUTION WITHOUT CURVATURE SINGULARITY

2013 ◽  
Vol 28 (30) ◽  
pp. 1350136 ◽  
Author(s):  
F. R. KLINKHAMER
Keyword(s):  
Black Hole ◽  
Black Hole Solution ◽  
Spherically Symmetric ◽  
Curvature Singularity ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Schwarzschild Solution ◽  
Connected Manifold ◽  
Gravity Effects ◽  
Simply Connected

An exact solution of the vacuum Einstein field equations over a nonsimply-connected manifold is presented. This solution is spherically symmetric and has no curvature singularity. It can be considered as a regularization of the Schwarzschild solution over a simply-connected manifold, which has a curvature singularity at the center. Spherically symmetric collapse of matter in ℝ4 may result in this nonsingular black-hole solution, if quantum-gravity effects allow for topology change near the center.

scholarly journals AdS Black Hole with Phantom Scalar Field

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Limei Zhang ◽  
Xiaoxiong Zeng ◽  
Zhonghua Li
Keyword(s):  
Black Hole ◽  
Black Hole Solution ◽  
Entanglement Entropy ◽  
Scalar Fields ◽  
Schwarzschild Black Hole ◽  
Ricci Flat ◽  
Large Black Hole ◽  
Phantom Scalar ◽  
Strip Geometry ◽  
Phantom Scalar Field

We present an AdS black hole solution with Ricci flat horizon in Einstein-phantom scalar theory. The phantom scalar fields just depend on the transverse coordinates x and y, which are parameterized by the parameter α. We study the thermodynamics of the AdS phantom black hole. Although its horizon is a Ricci flat Euclidean space, we find that the thermodynamical properties of the black hole solution are qualitatively the same as those of AdS Schwarzschild black hole. Namely, there exists a minimal temperature and the large black hole is thermodynamically stable, while the smaller one is unstable, so there is a so-called Hawking-Page phase transition between the large black hole and the thermal gas solution in the AdS space-time in Poincare coordinates. We also calculate the entanglement entropy for a strip geometry dual to the AdS phantom black holes and find that the behavior of the entanglement entropy is qualitatively the same as that of the black hole thermodynamical entropy.

scholarly journals Kerr–Schild–Kundt metrics in generic gravity theories with modified Horndeski couplings

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Metin Gürses ◽  
Yaghoub Heydarzade ◽  
Çetin Şentürk
Keyword(s):  
General Relativity ◽  
Plane Waves ◽  
Scalar Fields ◽  
Vacuum Field ◽  
Field Equations ◽  
Complete Proof ◽  
Universality Theorem ◽  
Covariant Derivatives ◽  
Matter Fields ◽  
Insight Into

AbstractThe Kerr–Schild–Kundt (KSK) metrics are known to be one of the universal metrics in general relativity, which means that they solve the vacuum field equations of any gravity theory constructed from the curvature tensor and its higher-order covariant derivatives. There is yet no complete proof that these metrics are universal in the presence of matter fields such as electromagnetic and/or scalar fields. In order to get some insight into what happens when we extend the “universality theorem” to the case in which the electromagnetic field is present, as a first step, we study the KSK class of metrics in the context of modified Horndeski theories with Maxwell’s field. We obtain exact solutions of these theories representing the pp-waves and AdS-plane waves in arbitrary D dimensions.

scholarly journals Quasinormal modes in the field of a dyon-like dilatonic black hole

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
A. N. Malybayev ◽  
K. A. Boshkayev ◽  
V. D. Ivashchuk
Keyword(s):  
Black Hole ◽  
Black Hole Solution ◽  
Dimensionless Parameter ◽  
Quasinormal Modes ◽  
Eikonal Approximation ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Test Field ◽  
Damping Rate ◽  
Dilatonic Black Hole

AbstractQuasinormal modes of massless test scalar field in the background of gravitational field for a non-extremal dilatonic dyonic black hole are explored. The dyon-like black hole solution is considered in the gravitational 4d model involving two scalar fields and two 2-forms. It is governed by two 2-dimensional dilatonic coupling vectors $${\lambda }_i$$ λ i obeying $${\lambda }_i ({\lambda }_1 + {\lambda }_2) > 0$$ λ i ( λ 1 + λ 2 ) > 0 , $$i =1,2$$ i = 1 , 2 . The first law of black hole thermodynamics is given and the Smarr relation is verified. Quasinormal modes for a massless scalar (test) field in the eikonal approximation are obtained and analysed. These modes depend upon a dimensionless parameter a ($$0 < a \le 2$$ 0 < a ≤ 2 ) which is a function of $${\lambda }_i$$ λ i . For limiting strong ($$a = +0$$ a = + 0 ) and weak ($$a = 2$$ a = 2 ) coupling cases, they coincide with the well-known results for the Schwarzschild and Reissner–Nordström solutions. It is shown that the Hod conjecture, connecting the damping rate and the Hawking temperature, is satisfied for $$0 < a \le 1$$ 0 < a ≤ 1 and all allowed values of parameters.

Thermodynamics of new black hole solutions in the Einstein–Maxwell-dilaton gravity

2018 ◽  
Vol 27 (07) ◽  
pp. 1850073 ◽  
Author(s):  
M. Dehghani
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Fields ◽  
Dilaton Gravity ◽  
Field Equations ◽  
Two Phase ◽  
Transition Analysis ◽  
Coupled Equations ◽  
Scalar Field Equations ◽  
Black Hole Solutions

In the present work, thermodynamics of the new black hole solutions to the four-dimensional Einstein–Maxwell-dilaton gravity theory have been studied. The dilaton potential, as the solution to the scalar field equations, has been constructed out by a linear combination of three Liouville-type potentials. Three new classes of charged dilatonic black hole solutions, as the exact solutions to the coupled equations of gravitational, electromagnetic and scalar fields, have been introduced. The conserved charge and mass of the new black holes have been calculated by utilizing Gauss's electric law and Abbott–Deser mass proposal, respectively. Also, the temperature, entropy and the electric potential of these new classes of charged dilatonic black holes have been calculated, making use of the geometrical approaches. Through a Smarr-type mass formula, the intensive parameters of the black holes have been calculated and validity of the first law of black hole thermodynamics has been confirmed. A thermal stability or phase transition analysis has been performed, making use of the canonical ensemble method. The heat capacity of the new black holes has been calculated and the points of type one- and type two-phase transitions as well as the ranges at which the new charged dilatonic black holes are locally stable have been determined, precisely.

scholarly journals ROTATING BLACK HOLES IN METRIC-AFFINE GRAVITY

2006 ◽  
Vol 15 (05) ◽  
pp. 635-668 ◽  
Author(s):  
PETER BAEKLER ◽  
FRIEDRICH W. HEHL
Keyword(s):  
Black Hole Solution ◽  
Lorentz Invariance ◽  
Linear Connection ◽  
Vacuum Field ◽  
Axially Symmetric ◽  
De Sitter ◽  
Field Equations ◽  
Rotating Black Holes ◽  
Affine Gravity ◽  
De Sitter Metric

Within the framework of metric-affine gravity (MAG, metric and an independent linear connection constitute space–time), we find, for a specific gravitational Lagrangian and by using prolongation techniques, a stationary axially symmetric exact solution of the vacuum field equations. This black hole solution embodies a Kerr–de Sitter metric and the post-Riemannian structures of torsion and nonmetricity. The solution is characterized by mass, angular momentum, and shear charge, the latter of which is a measure for violating Lorentz invariance.

scholarly journals Special dyon-like black hole solution in the model with two Abelian gauge fields and two scalar fields

2020 ◽  
Vol 1690 ◽  
pp. 012143
Author(s):  
F B Belissarova ◽  
K A Boshkayev ◽  
V D Ivashchuk ◽  
A N Malybayev
Keyword(s):  
Black Hole ◽  
Black Hole Solution ◽  
Scalar Fields ◽  
Gauge Fields ◽  
Abelian Gauge
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