Traversable Wormholes in a viable f(R)f(R)f(R) Gravity Model (original) (raw)
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New wormhole solutions in a viable f (R) gravity model
International Journal of Modern Physics D
Traversable wormhole solutions in General Relativity require exotic matter sources that violate the null energy condition (NEC), and such behavior may be avoided in modified gravity. In this study, we analyze the energy conditions for static, spherically symmetric traversable Morris–Thorne wormholes in a recently proposed viable [Formula: see text] gravity model. We numerically analyze solutions considering both constant and variable redshift functions, and present wormhole spacetimes respecting the NEC, supported by a phantom energy-like equation of state for the source. Moreover, we analyze the stability of the spacetimes using the generalized Tolman–Oppenheimer–Volkov equation. We demonstrate the effects of certain parameters in the [Formula: see text] model in determining energy condition violations, and establish that stable wormholes can be formulated only at the expense of violating the NEC.
Traversable Wormholes in a New f (R) Gravity Theory
2021
Traversable wormhole solutions in general relativity (GR) require exotic matter sources that violate the null energy condition. f(R) gravity has been studied extensively as a viable alternative to GR, and traversable wormhole solutions in f(R) gravity have been discussed extensively. In this study, we present a spherically symmetric traversable Morris-Thorne wormhole solution in a recently proposed f(R) gravity model with f(R) = R − α π Rc cot −1 ( R c R2 ) − β Rc [ 1 − exp ( − R Rc )] . We analyze the different energy conditions for our solution, and demonstrate that traversable wormholes can be realized in this theory.
Wormholes in viable f(R)$$ f ( R ) modified theories of gravity and weak energy condition
The European Physical Journal C, 2015
In this work wormholes in viable f (R) gravity models are analyzed. We are interested in exact solutions for stress-energy tensor components depending on different shape and redshift functions. Several solutions of gravitational equations for different f (R) models are examined. The solutions found imply no need for exotic material, while this need is implied in the standard general theory of relativity. A simple expression for weak energy condition (WEC) violation near the throat is derived and analyzed. High curvature regime is also discussed, as well as the question of the highest possible values of the Ricci scalar for which the WEC is not violated near the throat, and corresponding functions are calculated for several models. The approach here differs from the one that has been common since no additional assumptions to simplify the equations have been made, and the functions in f (R) models are not considered to be arbitrary functions, but rather a feature of the theory that has to be evaluated on the basis of consistency with observations for the Solar System and cosmological evolution. Therefore in this work we show that the existence of wormholes without exotic matter is not only possible in simple arbitrary f (R) models, but also in models that are in accordance with empirical data.
Quasi-cosmological traversable wormholes in f(R) gravity
The European Physical Journal C
In this paper, we study traversable wormholes in the context of f(R) gravity. Exact solutions of traversable wormholes are found by imposing the nonconstant Ricci scalar. These solutions asymptotically match spherical, flat and hyperbolic FRW metric. By choosing some static f(R) gravity models, we verify the standard energy conditions for the asymptotically spherical, flat and hyperbolic wormhole solutions. Unlike the Einstein gravity, we find that in the context of f(R) modified gravity, the asymptotically spherical, flat and hyperbolic wormhole solutions can respect the null energy condition (NEC) at the wormhole throat and near that. We find that in some static f(R) models, asymptotically flat and hyperbolic wormholes respect the weak energy condition (WEC) through the whole space.
Wormholes in viable f(R) modified theories of gravity and Weak Energy Condition
2014
In this work wormholes in viable f(R) gravity models are analysed. We are interested in exact solutions for stress-energy tensor components depending on different shape and redshift functions. Several solutions of gravitational equations for different f(R) models are examined. Found solutions imply no need for exotic material, while this need is implied in the standard general theory of relativity. A simple expression for WEC violation near the throat is derived and analysed. High curvature regime is also discussed, as well as the question of the highest possible values of the Ricci scalar for which the WEC is not violated near the throat, and corresponding functions are calculated for several models. The approach here differs from the one that has been common since no additional assumptions to simplify the equations have been made, and functions in f(R) models are not considered to be arbitrary functions, but rather a feature of the theory that has to be evaluated on the basis of c...
Morris–Thorne wormholes in modified f(R, T) gravity
General Relativity and Gravitation
Wormhole solutions obtained by Morris and Thorne (MT) in general relativity (GR) is investigated in a modified theory of gravity. In the gravitational action, we consider f (R, T) which is a function of the Ricci scalar (R) and the trace of the energy momentum tensor (T). In the framework of a modified gravity described by f (R, T) = R + αR 2 + λT , where α and λ are constants, MT wormhole solutions (WH) with normal matter are obtained for a relevant shape function. The energy conditions are probed at the throat and away from the throat of the WH. It is found that the coupling parameters, α and λ in the gravitational action play an important role to decide the matter composition needed. It is found that for a given λ, WH exists in the presence of exotic matter at the throat when α < 0. However, it is demonstrated that the WH exists without exotic matter when α > 0 in the modified gravity. Two different shape functions are analyzed for the WH solutions that admits with or without exotic matter. It is noted that in a modified gravity MT WH permits even with normal matter which is not possible in GR. It is shown that a class of WH solutions exist with anisotropic fluid for λ = −8π. However, for flat asymptotic regions with anisotropic fluids WH solutions cannot be realized for λ = −8π. All the energy conditions are found consistent with the hybrid shape function indicating existence of WH even with normal matter for λ → 0.
Wormholes satisfying the Energy Conditions in f(R) Gravity and Non-commutative Geometry
2022
Traversable wormhole solutions in general relativity (GR) require exotic matter sources that violate the null energy condition, and such exotic behavior may be avoided in f (R) modified gravity. Moreover, the concept of non-commutative geometry as a gravitational source can be leveraged both in GR and modified gravity to realize nontrivial space-time configurations. In this study, we investigate a viable f (R) gravity model and non-commutative geometry to analyze spherically symmetric traversable Morris-Thorne wormhole solutions. We analyze the different energy conditions, and demonstrate that wormholes satisfying the energy conditions can be realized in both frameworks.
Traversable wormholes in f(R) massive gravity
Physical Review D
In this work, the study of traversable wormholes in fðRÞ massive gravity with the function fðRÞ ¼ R þ α 1 R n , where α 1 and n are arbitrary constants, is considered. We choose the shape function of the form bðrÞ ¼ r expð−αðr − r 0 ÞÞ with α and r 0 being an arbitrary constant and a radius of the wormhole throat, respectively. Here α affects the radius of curvature of the wormhole. We consider a spherically symmetric and static wormhole metric and derive field equations. Moreover, we visualize the wormhole geometry using embedding diagrams. Furthermore, we check the null, weak, dominant, and strong energy conditions at the wormhole throat with a radius r 0 invoking three types of redshift functions, Φ ¼ constant, γ 1 =r, logð1 þ γ 2 =rÞ with γ 1 and γ 2 are arbitrary real constants. We also compute the volume integral quantifier to calculate the amount of the exotic matter near the constructed wormhole throat.
TIME-DEPENDENT WORMHOLE SOLUTIONS OF f(R) THEORY OF GRAVITY AND ENERGY CONDITIONS
Modern Physics Letters A, 2011
In this work, we construct time-dependent wormhole solutions in the context of f(R) theory of gravity. The background matter is considered to be traceless. By considering specific shape function and power-law expansion, exact solutions for f(R) are found. The null and the weak energy conditions (NEC and WEC) are checked for wormhole solutions. It is shown that the matter threading the wormhole spacetimes with either accelerated expansion or decelerated expansion satisfies the NEC and WEC. Read More: http://www.worldscientific.com/doi/abs/10.1142/S0217732311035547?queryID=34%2F1199469
arXiv (Cornell University), 2020
We consider the f (R, T) theory of gravity, in which the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor, to study static spherically symmetric wormhole geometries sustained by matter sources with isotropic pressure. According to restrictions on the wormhole geometries, we carefully adopt different strategies to construct solutions with the properties and characteristics of wormholes. Using an utterly general procedure, we provide several examples of wormholes in which the matter threading the wormhole throat satisfies all of the energy conditions and discuss general mechanisms for finding them. Finally, we postulate a smooth transformation for simplifying the nonlinear field equations and have more consistent results than the other ones to conclude that the results can be viewed as specific exact wormhole solutions without exotic matter.