Stable wormhole models in general relativity under conformal symmetry

2021 ◽  
Vol 18 (03) ◽  
pp. 2150041
Author(s):  
Asifa Ashraf ◽  
Zhiyue Zhang
Keyword(s):  
General Relativity ◽  
Symmetric Space ◽  
Conformal Symmetry ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Anisotropic Fluid ◽  
Spherically Symmetric ◽  
Shape Functions ◽  
The Stability ◽  
Tov Equation

In this study, we shall explore conformal symmetry to examine the wormhole models by considering traceless fluid. In this regard, we shall take anisotropic fluid with spherically symmetric space-time. Further, we shall calculate the properties of shape-functions, which are necessary for the existence of wormhole geometry. The presence of exotic matter is confirmed in all the cases through the violation of the Null Energy Condition. Furthermore, we have discussed the stability of wormhole solutions through the Tolman–Oppenheimer–Volkoff (TOV) equation. It is observed that our acquired solutions are stable under the particular values of involved parameters in different cases in conformal symmetry.

scholarly journals Wormhole Models and Energy Conditions in f ℛ Gravity with the Hu–Sawicki Model

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Ouziala Ikram ◽  
G. Mustafa
Keyword(s):  
Equation Of State ◽  
Symmetric Space ◽  
Shape Function ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Space Time ◽  
Energy Conditions ◽  
Fluid Distribution ◽  
Anisotropic Fluid ◽  
Nature Of Matter

In this recent study, we shall investigate the wormhole models with a Hu–Sawicki model in the framework of f ℛ gravity. Spherically static symmetric space-time is considered to construct wormhole models with the anisotropic fluid distribution. The traceless matter is discussed by imposing a particular equation of state. To address the important conditions of the shape function of the wormhole geometry, we have used the particular values of the involved parameters. Furthermore, different energy conditions are discussed to check the nature of matter against two specific models. The null energy condition is observed to be violated for both of the models. It is mentioned that our inquired results are acceptable.

scholarly journals Stable Wormholes in the Background of an Exponential f(R) Gravity

Universe ◽  
2020 ◽  
Vol 6 (4) ◽  
pp. 48 ◽  
Author(s):  
Ghulam Mustafa ◽  
Ibrar Hussain ◽  
M. Farasat Shamir
Keyword(s):  
Stability Analysis ◽  
Equation Of State ◽  
Shape Function ◽  
Energy Condition ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Spherically Symmetric ◽  
Shape Functions ◽  
Spacetime Geometry ◽  
Specific Shape

The current paper is devoted to investigating wormhole solutions with an exponential gravity model in the background of f ( R ) theory. Spherically symmetric static spacetime geometry is chosen to explore wormhole solutions with anisotropic fluid source. The behavior of the traceless matter is studied by employing a particular equation of state to describe the important properties of the shape-function of the wormhole geometry. Furthermore, the energy conditions and stability analysis are done for two specific shape-functions. It is seen that the energy condition are to be violated for both of the shape-functions chosen here. It is concluded that our results are stable and realistic.

Wormhole models with exotic matter in Rastall gravity

2020 ◽  
Vol 17 (10) ◽  
pp. 2050146
Author(s):  
G. Mustafa ◽  
Tie-Cheng Xia
Keyword(s):  
Shape Function ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Shape Functions ◽  
Anisotropic Models ◽  
Specific Shape

In this paper, we examine the wormhole solutions by taking two different anisotropic models in Rastall gravity. For this purpose, we shall discuss anisotropic fluid to construct two different anisotropic models. Further, we shall employ two specific shape functions to calculate the behavior of energy conditions. The presence of exotic matter is confirmed in all the cases of this study due to the violation of the null energy condition. All the properties of shape function under both anisotropic models are fulfilled. It is noticed that wormhole solutions exist under the particular values of involved parameters in different cases in Rastall gravity.

scholarly journals Wormhole geometries in f(Q) gravity and the energy conditions

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
Ayan Banerjee ◽  
Anirudh Pradhan ◽  
Takol Tangphati ◽  
Farook Rahaman
Keyword(s):  
Energy Condition ◽  
Null Energy Condition ◽  
Specific Form ◽  
Energy Conditions ◽  
Recent Theory ◽  
Spherically Symmetric ◽  
Shape Functions ◽  
Field Equations ◽  
Form Function

AbstractFollowing the recent theory of f(Q) gravity, we continue to investigate the possible existence of wormhole geometries, where Q is the non-metricity scalar. Recently, the non-metricity scalar and the corresponding field equations have been studied for some spherically symmetric configurations in Mustafa (Phys Lett B 821:136612, 2021) and Lin and Zhai (Phys Rev D 103:124001, 2021). One can note that field equations are different in these two studies. Following Lin and Zhai (2021), we systematically study the field equations for wormhole solutions and found the violation of null energy conditions in the throat neighborhood. More specifically, considering specific choices for the f(Q) form and for constant redshift with different shape functions, we present a class of solutions for static and spherically symmetric wormholes. Our survey indicates that wormhole solutions could not exist for specific form function $$f(Q)= Q+ \alpha Q^2$$ f ( Q ) = Q + α Q 2 . To summarize, exact wormhole models can be constructed with violation of the null energy condition throughout the spacetime while being $$\rho \ge 0$$ ρ ≥ 0 and vice versa.

Traversable wormhole modelling with exponential and hyperbolic shape functions in F(R,T) framework

2020 ◽  
Vol 35 (25) ◽  
pp. 2050149
Author(s):  
Shweta ◽  
Ambuj Kumar Mishra ◽  
Umesh Kumar Sharma
Keyword(s):  
Shape Function ◽  
Energy Condition ◽  
Gravitational Theory ◽  
Null Energy Condition ◽  
Relativity Theory ◽  
Shape Functions ◽  
Traversable Wormhole ◽  
Hydrostatic Force ◽  
State Formula ◽  
The Stability

The concept of traversable wormhole, a hypothetical tunnel-like structure is initially proposed by Morris and Thorne (Am. J. Phys. 56, 395 (1988)) by using Einstein’s general relativity theory. Harko et al. (Phys. Rev. D 84, 024020 (2011)) defined [Formula: see text] gravity as an extended gravitational theory having terms [Formula: see text] and [Formula: see text] as Ricci scalar and trace of energy momentum respectively. In this article, we explore wormhole models for the framework of [Formula: see text] gravity by using two different shape functions. The first shape function is [Formula: see text], [Formula: see text] (proposed by Mishra and Sharma, arXiv:2003.00298v1 , 2020) and second is a hyperbolic shape function which is of the form [Formula: see text]. Geometrical behavior of wormholes are discussed in anisotropic scenario by using equation of state [Formula: see text]. The stability of models are analyzed by using equilibrium condition and determining gravitational force, anisotropic force, hydrostatic force and force due to modified gravity. For the validation of null energy condition and weak energy condition, significant role of shape function is illustrated for the presence of nonexotic matter.

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.

Stability of charged neutron star in Palatini f(R) gravity

2019 ◽  
Vol 34 (31) ◽  
pp. 1950252 ◽  
Author(s):  
M. Z. Bhatti ◽  
Z. Yousaf ◽  
Zarnoor
Keyword(s):  
Chemical Composition ◽  
Neutron Star ◽  
Modified Gravity ◽  
Equilibrium Equation ◽  
Hydrostatic Equilibrium ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Symmetric Geometry ◽  
The Stability ◽  
Tov Equation

In this work, we discuss the stability of charged neutron star in the background of [Formula: see text] gravity and construct the generalized Tolman–Oppenheimer–Volkoff (TOV) equations. For this, we consider static spherically symmetric geometry to construct the hydrostatic equilibrium equation and deduce TOV equations from modified field equations with electromagnetic effects. We conclude that the generalized TOV equation depicts the stable stars configuration independent of the generic function of the modified gravity if the condition of uniform entropy and chemical composition is assumed.

Wormhole structures and energy conditions in f(ℛ) gravity with hybrid shape functions

2021 ◽  
pp. 2150065
Author(s):  
Ouziala Ikram ◽  
Mushtaq Ahmad ◽  
G. Mustafa
Keyword(s):  
Energy Condition ◽  
Null Energy Condition ◽  
Graphical Analysis ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Collective Effects ◽  
Shape Functions ◽  
Energy Constraints ◽  
Modified Formula ◽  
Two Hybrid

This paper discusses the possible wormhole solutions in modified [Formula: see text] gravity by employing the two hybrid shape functions i.e. [Formula: see text] and [Formula: see text], where [Formula: see text] is constant. The solutions are accomplished by implementing the modified-gravity functions [Formula: see text] and [Formula: see text], where [Formula: see text]. It is presented by investigating the energy constraints through the graphical analysis that the null energy conditions for the energy–momentum tensor are largely violated for our both models. Energy constraints connected to the matter source threading the possible wormhole structures are in general worked out, supporting the null energy constraints in the neighborhood of the wormhole neck. This concludes that threaded by the matter, the existence of the non-exotic wormhole geometries have been found in this gravity. Subsequently, it is shown that violation of the null energy condition may be accredited to the collective effects of the [Formula: see text] gravity and owing to the non-commutative geometry.

Anisotropic fluid spheres satisfying the Karmarkar condition

2019 ◽  
Vol 34 (15) ◽  
pp. 1950113 ◽  
Author(s):  
Nayan Sarkar ◽  
Susmita Sarkar ◽  
Farook Rahaman ◽  
Ksh. Newton Singh ◽  
Hasrat Hussain Shah
Keyword(s):  
Compact Stars ◽  
Anisotropic Fluid ◽  
Stability Factor ◽  
Spherically Symmetric ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Suitable Form ◽  
Fluid Spheres ◽  
Interior Solutions ◽  
Tov Equation

In this paper, we present new physically viable interior solutions of the Einstein field equations for static and spherically symmetric anisotropic compact stars satisfying the Karmarkar condition. For presenting the exact solutions, we provide a new suitable form of one of the metric potential functions. Obtained solutions satisfy all the physically acceptable properties of realistic fluid spheres and hence solutions are well-behaved and representing matter distributions are in equilibrium state and potentially stable by satisfying the TOV equation and the condition on stability factor, adiabatic indices. We analyze the solutions for two well-known compact stars Vela X-1 (Mass = 1.77 M[Formula: see text], R = 9.56 km) and Cen X-3 (Mass = 1.49 M[Formula: see text], R = 9.17 km).

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