8 results
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2. Thin-shell wormholes with AdS black holes surrounded by Chaplygin dark fluid.
- Author
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Javed, Faisal, Waseem, Arfa, Mustafa, Ghulam, and Güdekli, Ertan
- Subjects
- *
EQUATIONS of state , *FLUIDS , *ENERGY density , *DARK energy - Abstract
In this paper, we inspect the stable geometry of thin-shell wormholes in the background of static spherically-symmetric AdS black holes solution bounded by dark fluid and Chaplygin-like equation of state p = − ℬ / ρ , where p and ρ denote the pressure and energy density that are related through positive constant ℬ. For this purpose, we consider the two equivalent copies of black holes and connected them at the hypersurface through cut and paste approach. Then, we employ the linearized radial perturbation to discuss the stability of the developed wormhole geometry by assuming variable equations of state. We obtain the maximum stable configuration for massive black holes for both barotropic and Chaplygin variable equations of state while for higher values of n , stable regions decrease. It is found that for every selection of physical parameters of black hole geometry with low intensity of Chaplygin dark fluid, we get the stable configuration of thin-shell wormholes. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. Impact of f(ℜ,2) theory on stable Finch–Skea gravastar model.
- Author
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Sharif, M. and Naz, Saba
- Subjects
- *
BLACK holes , *GRAVITY , *SPACETIME , *ENTROPY , *DARK energy , *REDSHIFT - Abstract
This paper examines the structure of a gravitational vacuum star (also known as gravastar) in the background of f (ℜ , 2) theory. This hypothetical object can be treated as a substitute of a black hole, with three regions: (i) the internal region, (ii) the intrinsic shell and (iii) the outer region. We examine these geometries using Finch–Skea metric for the radial metric component along with the particular f (ℜ , 2) model. We determine singularity-free solutions for both the inner as well as thin-shell domains. The smooth matching of the interior region with external Schwarzschild spacetime is obtained through Israel matching constraints. Finally, we study various characteristics of gravastar domains including the equation-of-state parameter, proper length, entropy, energy as well as surface redshift. It is found that the compact gravastar structure is a viable alternate to the black hole in the perspective of this gravity. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
4. Effects of variable equations of state on the stability of nonlinear electrodynamics thin-shell wormholes.
- Author
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Javed, Faisal, Fatima, G., Mustafa, G., and Övgün, Ali
- Subjects
- *
ELECTRODYNAMICS , *SCHWARZSCHILD black holes , *COUPLING constants , *BLACK holes - Abstract
This paper explores the role of nonlinear electrodynamics on the stable configuration of thin-shell wormholes formulated from two equivalent geometries of Reissner–Nordström black hole with nonlinear electrodynamics. For this purpose, we use cut and paste approach to eliminate the central singularity and event horizons of the black hole geometry. Then, we explore the stability of the developed model by considering different types of matter distribution located at thin-shell, i.e. barotropic model and variable equations of state (phantomlike variable and Chaplygin variable models). We use linearized radial perturbation to explore the stable characteristics of thin-shell wormholes. It is interesting to mention that Schwarzschild and Reissner–Nordström black holes show the unstable configuration for such type of matter distribution while Reissner–Nordström black hole with nonlinear electrodynamics expresses stable regions. It is found that the presence of nonlinear electrodynamics gives the possibility of a stable structure for barotropic as well as variable models. It is concluded that stable region increases for these models by considering higher negative values of coupling constant α and the real constant n. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
5. Analysis of charged self-gravitational complex structures evolving quasi-homologously.
- Author
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Yousaf, Z., Bhatti, M. Z., and Khan, Suraj
- Subjects
- *
ORTHOGONAL decompositions , *ELECTRIC charge , *EINSTEIN field equations - Abstract
This paper studies the complex mechanism of evolving charged self-gravitational (dissipating or non-dissipating) systems using a structure scalar Y T F , resulting from the basic procedure of orthogonal decomposition of the Riemann–Christoffel curvature tensor. The influence of electrical charge on the complexity of the considered system is analyzed in detail. We find several analytical Einstein–Maxwell models fulfilling the quasi-homologous ( Q H ) evolution plus the vanishing complexity factor ( C F ′ ) condition. Few of the presented models fulfill the Darmois constraints and exhibit shells, however, others satisfy the Israel constraints on both the boundary surfaces. Finally, some possible applications of the presented solutions are mentioned, which are important from astrophysical stand points. It is expected that some of the provided evolving Einstein–Maxwell fluid configurations may be utilized as a toy model of general frameworks like supernova explosions. It is found that the Q H implies the vanishing of the C F and gives rise to a unique and simplest configuration (Friedmann–Lemaître–Robertson–Walker model) fulfilling the condition Y T F = 0 and evolving in the Q H regime. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
6. Gravastars with Karmarkar condition in f(ℜ,2) gravity.
- Author
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Sharif, M. and Naz, Saba
- Subjects
- *
GRAVITY , *EQUATIONS of state , *BLACK holes , *SURFACE pressure , *ENTROPY - Abstract
This paper examines the structure of gravastar (gravitationally vacuum star) in the background of f (ℜ , 2) theory. The gravastar can be regarded as a substitute for a black hole comprising of three regions (i) the interior domain, (ii) the intrinsic shell and (iii) the exterior domain. We investigate these domains by employing Karmarkar's condition by assuming a specific f (ℜ , 2) model. The field equations are solved to evaluate nonsingular solutions of both the interior and intermediate regions. Inner as well as outer spacetimes are matched together using Israel formalism to obtain density and pressure at the joining surface. Different attributes of gravastar like the equation of state parameter, proper length, entropy and energy are analyzed through graphical behavior. It is found that the gravastar model is a viable alternative to the black hole in the context of this gravity. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
7. Gravastars in energy–momentum squared gravity.
- Author
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Sharif, M. and Naz, Saba
- Subjects
- *
GRAVITY , *EQUATIONS of state , *SURFACE pressure , *BLACK holes , *ENTROPY , *MOMENTUM transfer - Abstract
This paper is devoted to studying the structure of gravitationally vacuum condensate stars under the influence of matter and geometry coupled gravity. This alternative to black hole comprises three domains, i.e. interior, exterior and thin-shell. We investigate such regions by considering particular equations of state for a specific model of energy–momentum squared gravity. The nonsingular solutions of field equations are obtained to describe the interior region of gravastar and the Schwarzschild spacetime represents the exterior region. The junction conditions are used to match interior and exterior domains while Lanczos equations provide the surface density and pressure at thin-shell. We investigate various attributes of gravastar such as the equation of state parameter, entropy, proper length as well as energy. The physical features of a gravitationally vacuum star indicate a linear relationship with the thickness of the shell and provide a viable structure similar to general relativity. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
8. Formation of cylindrical gravastars in modified gravity.
- Author
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Yousaf, Z., Bhatti, M. Z., and Bamba, Kazuharu
- Subjects
- *
BLACK holes , *ENTROPY - Abstract
In this paper, we analyze a few physical characteristics of gravastar with cylindrical geometry in f (R , T) theory, where R is the Ricci scalar and T is the trace of energy-momentum tensor. The gravastar is generally considered to be a substitute of a black hole with three different regions. In this work, we examine the formulation of gravastar-like cylindrical structures in f (R , T) theory. By using Darmois and Israel matching conditions, we formulate a mass function of a thin shell. We calculate the different physical characteristics of gravastar, in particular, entropy within the thin shell, proper length of the intermediate thin shell as well as energy of the shell. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
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