Traversable wormholes in f(R,T)f(R,T)f(R,T) gravity satisfying the null energy condition with isotropic pressure (original) (raw)
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Wormholes in f(R,T)f(R,T)f(R,T) gravity satisfying the null energy condition with isotropic pressure
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.
Conformally symmetric traversable wormholes in f(R,T)f(R,T)f(R,T) gravity
arXiv (Cornell University), 2019
To find more deliberate f (R, T) astrophysical solutions, we proceed by studying wormhole geometries under the assumption of spherical symmetry and the existence of a conformal Killing symmetry to attain the more acceptable astrophysical results. To do this, we consider a more plausible and simple model f (R, T) = R + 2χT , where R is the Ricci scalar and T = −ρ + pr + 2pt denotes the trace of the energy-momentum tensor of the matter content. We explore and analyze two cases separately. In the first part, wormhole solutions are constructed for the matter sources with isotropic pressure. However, the obtained solution does not satisfy the required wormhole conditions. In the second part, we introduce an EoS relating to pressure (radial and lateral) and density. We constrain the models with phantom energy EoS i.e. ω = pr/ρ < −1, consequently violating the null energy condition. Next, we analyze the model via pt = npr. Several physical properties and characteristics of these solutions are investigated which are consistent with previous references about wormholes. We mainly focus on energy conditions (NEC, WEC and SEC) and consequently for supporting the respective wormhole geometries in details. In both cases it is found that the energy density is positive as seen by any static observer. To support the theoretical results, we also plotted several figures for different parameter values of the model that helps us to confirm the predictions. Finally, the volume integral quantifier, which provides useful information about the total amount of exotic matter required to maintain a traversable wormhole is discussed briefly.
Traversable wormholes in the traceless f(R,T) gravity
International Journal of Modern Physics D
Wormholes are tunnels connecting different regions in spacetime. They were obtained originally as a solution for Einstein’s General Theory of Relativity and according to this theory they need to be filled by an exotic kind of anisotropic matter. In the present sense, by “exotic matter” we mean matter that does not satisfy the energy conditions. In this paper, we propose the modeling of traversable wormholes (i.e. wormholes that can be safely crossed) within an alternative gravity theory that proposes an extra material (rather than geometrical) term in its gravitational action, namely the traceless [Formula: see text] theory of gravitation, with [Formula: see text] and [Formula: see text] being, respectively, the Ricci scalar and trace of the energy–momentum tensor. Our solutions are obtained from well-known particular cases of the wormhole metric potentials, namely redshift and shape functions. In possession of the solutions for the wormhole material content, we also apply the energ...
Traversable wormholes in f(R,T)$f(R,T)$ gravity
Astrophysics and Space Science
In the present article, models of traversable wormholes within the f (R, T) modified gravity theory are investigated. We have presented some wormhole models, developed from various hypothesis for the substance of their matter, i.e. various relationships with their components of pressure (lateral and radial). The solutions found for the shape functions of the wormholes produced complies with the required metric conditions. The suitability of solution is examined by exploring null, strong and dominant energy conditions. It is surmised that the normal matter in the throat may pursue the energy conditions yet the gravitational field exuding from the adjusted gravity hypothesis support the appearance of the non-standard geometries of wormholes.
Static Traversable Wormholes in f(R,T)=R+2αlnT Gravity
Chinese Journal of Physics
Traversable wormholes, studied by Morris and Thorne in general relativity, are investigated in this research paper in f (R, T ) gravity by introducing a new form of nonlinear f (R, T ) function. By using this novel function, the Einstein's field equations in f (R, T ) gravity are derived. To obtain the exact wormhole solutions, the relations p t = ωρ and p r = sinh(r)p t , where ρ is the energy density, p r is the radial pressure and p t is the tangential pressure, are used. Other than these relations, two forms of shape function defined in literature are used, and their suitability is examined by exploring the regions of validity of null, weak, strong and dominant energy conditions . Consequently, the radius of the throat or the spherical region, with satisfied energy conditions, is determined and the presence of exotic matter is minimized.
Wormholes in a viable f (T) gravity
2013
In this paper, we derive some new exact solutions of static wormholes in f (T ) gravity. We discuss independent cases of the pressure components including isotropic and anisotropic pressure. Lastly we consider radial pressure satisfying a barotropic equation of state. We also check the behavior of null energy condition (NEC) for each case and observe that it is violated for anisotropic while it is satisfied for isotropic and barotropic cases.
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.
Advances in Astronomy, 2021
In Einstein’s relativity theory, the existence of traversable wormholes requires the involvement of exotic matter which violates the null energy condition (NEC). Our aim, in this article, is to construct wormhole solutions with the nonexotic matter. To achieve this, we choose an interesting gravitational framework of f ℛ , T theory which contains a quadratic term of energy-momentum tensor T i j trace and a well-known Starobinsky f ℛ model in its extended form. We analyze the behavior of energy constraints in the framework of f ℛ , T = ℛ + α ℛ 2 + γ ℛ n + λ T 2 (where α , γ , and λ are some random constants) model for the well-proposed shape function S r = r 0 r 0 / r ε (where ε is a constant and r 0 is the wormhole throat). A detailed analysis of validity regions is presented for some choices of coupling parameters along with the free parameter of EoS β , m . It is shown that, under this model, the existence of viable wormhole geometry is possible without requiring any exotic matter.
Study of static wormhole solutions in F(T,TG) gravity
Annals of Physics
In this paper, we investigate static spherically symmetric wormhole solutions in the background of F (T, T G) gravity (T is the torsion scalar and T G represents teleparallel equivalent of the Gauss-Bonnet term). We study the wormhole solutions by assuming four different matter contents, a specific redshift function and a particular F (T, T G) model. The behavior of null/weak energy conditions for these fluids is analyzed graphically. It turns out that wormhole solutions can be obtained in the absence of exotic matter for some particular regions of spacetime. We also explore stability of wormhole solutions through equilibrium condition. It is concluded that there exist physically acceptable wormhole solutions for anisotropic, isotropic and traceless fluids.
Traversable Wormholes in a viable f(R)f(R)f(R) Gravity Model
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 analyze the energy conditions for spherically symmetric traversable Morris-Thorne wormholes in a recently proposed viable f(R) gravity model. We analyze wormhole space-times considering both constant and variable redshift functions, and demonstrate that traversable wormholes can be realized in this theory with minimal or no violations of the null energy condition with suitable choices of model and metric parameters.