scholarly journals Exact black hole solutions with a conformally coupled scalar field and dynamic Ricci curvature in f(R) gravity theories

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Thanasis Karakasis ◽  
Eleftherios Papantonopoulos ◽  
Zi-Yu Tang ◽  
Bin Wang
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Modified Gravity ◽  
Black Hole Solution ◽  
Gordon Equation ◽  
The Self ◽  
Asymptotically Flat ◽  
Dimensional Spacetime ◽  
Klein Gordon ◽  
Black Hole Solutions

AbstractWe report exact black hole solutions in asymptotically flat or (A)dS four-dimensional spacetime with a conformally coupled self-interacting scalar field in f(R) gravity. We first consider the asymptotically flat model $$f(R) = R -2\alpha \sqrt{R}$$ f ( R ) = R - 2 α R and derive an exact black hole solution. Then, we consider the asymptotically (A)dS model $$f(R) =R -2 \Lambda -2 \alpha \sqrt{R-4 \Lambda }$$ f ( R ) = R - 2 Λ - 2 α R - 4 Λ and derive an exact black hole solution. In both cases the modified gravity parameter $$\alpha $$ α , which has the dimension of the inverse mass, cannot be set to zero and the self-interacting potential is determined from the Klein–Gordon equation, preserving the conformal invariance. The thermodynamics of the solutions is also studied.

scholarly journals New five-dimensional Bianchi type magnetically charged hairy topological black hole solutions in string theory

2019 ◽  
Vol 79 (12) ◽  
Author(s):  
F. Naderi ◽  
A. Rezaei-Aghdam
Keyword(s):  
Black Hole ◽  
Black Hole Solution ◽  
Bianchi Type ◽  
Magnetic Charge ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Five Dimensions ◽  
Asymptotically Flat ◽  
Black Hole Solutions ◽  
Three Dimensional Space

AbstractWe construct black hole solutions to the leading order of string effective action in five dimensions with the source given by dilaton and magnetically charged antisymmetric gauge B-field. Presence of the considered B-field leads to the unusual asymptotic behavior of the solutions which are neither asymptotically flat nor asymptotically (A)dS. We consider the three-dimensional space part to correspond to the Bianchi classes and so the horizons of these topological black hole solutions are modeled by seven homogeneous Thurston’s geometries of $$E^3$$E3, $$S^3$$S3, $$H^3$$H3, $$ H^2 \times E^1$$H2×E1, $$\widetilde{{SL_2R}}$$SL2R~, nilgeometry, and solvegeometry. Calculating the quasi-local mass, temperature, entropy, dilaton charge, and magnetic potential, we show that the first law of black hole thermodynamics is satisfied by these quantities and the dilaton charge is not independent of mass and magnetic charge. Furthermore, for Bianchi type V, the T-dual black hole solution is obtained which carries no charge associated with B-field and the entropy turns to be invariant under the T-duality.

scholarly journals The Klein–Gordon equation of a rotating charged hairy black hole in (2 + 1) dimensions

2016 ◽  
Vol 31 (09) ◽  
pp. 1650057 ◽  
Author(s):  
B. Pourhassan
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Gordon Equation ◽  
Black Hole Horizon ◽  
Massive Scalar Field ◽  
Black Hole Background ◽  
Special Cases ◽  
Klein Gordon ◽  
Hairy Black Hole ◽  
Klein Gordon Equation

In this paper, we consider the Klein–Gordon equation in a 3D charged rotating hairy black hole background to study behavior of a massive scalar field. In the general case, we find periodic-like behavior for the scalar field which may vanish at the black hole horizon or far from the black hole horizon. For the special cases of non-rotating or near horizon approximation, we find radial solution of Klein–Gordon equation in terms of hypergeometric and Kummer functions. Also for the case of uncharged black hole, we find numerical solution of the Klein–Gordon equation as periodic function which may enhance out of the black hole or vanish at horizon. We find allowed boundary conditions which may yield to the identical bosons described by scalar field.

scholarly journals Black hole solutions in modified gravity induced by quantum metric fluctuations

2021 ◽  
Vol 31 ◽  
pp. 100756
Author(s):  
Jin-Zhao Yang ◽  
Shahab Shahidi ◽  
Tiberiu Harko ◽  
Shi-Dong Liang
Keyword(s):  
Black Hole ◽  
Modified Gravity ◽  
Black Hole Solutions ◽  
Metric Fluctuations

scholarly journals Spinning boson stars and hairy black holes with nonminimal coupling

2018 ◽  
Vol 27 (11) ◽  
pp. 1843009 ◽  
Author(s):  
Carlos A. R. Herdeiro ◽  
Eugen Radu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Field ◽  
Coupling Parameter ◽  
Nonminimal Coupling ◽  
Boson Stars ◽  
Hairy Black Holes ◽  
Black Hole Solutions ◽  
Hairy Black Hole ◽  
Coupled Theory

We obtain spinning boson star solutions and hairy black holes with synchronized hair in the Einstein–Klein–Gordon model, wherein the scalar field is massive, complex and with a nonminimal coupling to the Ricci scalar. The existence of these hairy black holes in this model provides yet another manifestation of the universality of the synchronization mechanism to endow spinning black holes with hair. We study the variation of the physical properties of the boson stars and hairy black holes with the coupling parameter between the scalar field and the curvature, showing that they are, qualitatively, identical to those in the minimally coupled case. By discussing the conformal transformation to the Einstein frame, we argue that the solutions herein provide new rotating boson star and hairy black hole solutions in the minimally coupled theory, with a particular potential, and that no spherically symmetric hairy black hole solutions exist in the nonminimally coupled theory, under a condition of conformal regularity.

ENTROPY OF SCHWARZSCHILD–de SITTER BLACK HOLE IN NON-THERMAL-EQUILIBRIUM

2001 ◽  
Vol 16 (11) ◽  
pp. 719-723 ◽  
Author(s):  
REN ZHAO ◽  
JUNFANG ZHANG ◽  
LICHUN ZHANG
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Thermal Equilibrium ◽  
Gordon Equation ◽  
Brick Wall ◽  
De Sitter ◽  
Logarithmic Term ◽  
Klein Gordon ◽  
Klein Gordon Equation ◽  
Wall Method

Starting from the Klein–Gordon equation, we calculate the entropy of Schwarzschild–de Sitter black hole in non-thermal-equilibrium by using the improved brick-wall method-membrane model. When taking the proper cutoff in the obtained result, we obtain that both black hole's entropy and cosmic entropy are proportional to the areas of event horizon. We avoid the logarithmic term and stripped term in the original brick-wall method. It offers a new way of studying the entropy of the black hole in non-thermal-equilibrium.

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 Absorption Cross Section and Decay Rate of Dilatonic Black Strings

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Huriye Gürsel ◽  
İzzet Sakallı
Keyword(s):  
Scalar Field ◽  
Decay Rate ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Gordon Equation ◽  
Absorption Cross ◽  
Black String ◽  
Yang Mills ◽  
Klein Gordon ◽  
Analytical Expressions

We studied in detail the propagation of a massive tachyonic scalar field in the background of a five-dimensional (5D) Einstein–Yang–Mills–Born–Infeld–dilaton black string: the massive Klein–Gordon equation was solved, exactly. Next we obtained complete analytical expressions for the greybody factor, absorption cross section, and decay rate for the tachyonic scalar field in the geometry under consideration. The behaviors of the obtained results are graphically represented for different values of the theory’s free parameters. We also discuss why tachyons should be used instead of ordinary particles for the analytical derivation of the greybody factor of the dilatonic 5D black string.

scholarly journals General black hole solutions in ( 2+1 )-dimensions with a scalar field nonminimally coupled to gravity

2019 ◽  
Vol 100 (2) ◽  
Author(s):  
Zi-Yu Tang ◽  
Yen Chin Ong ◽  
Bin Wang ◽  
Eleftherios Papantonopoulos
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Black Hole Solutions
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