New wormhole solutions in a viable 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.

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.

Universe, 2020

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.

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.

Journal of Cosmology and Astroparticle Physics, 2014

We consider novel wormhole solutions supported by a matter content that minimally violates the null energy condition. More specifically, we consider an equation of state in which the sum of the energy density and radial pressure is proportional to a constant with a value smaller than that of the inverse area characterising the system, i.e., the area of the wormhole mouth. This approach is motivated by a recently proposed cosmological event, denoted "the little sibling of the big rip", where the Hubble rate and the scale factor blow up but the cosmic derivative of the Hubble rate does not [1]. By using the cut-andpaste approach, we match interior spherically symmetric wormhole solutions to an exterior Schwarzschild geometry, and analyse the stability of the thin-shell to linearized spherically symmetric perturbations around static solutions, by choosing suitable properties for the exotic material residing on the junction interface radius. Furthermore, we also consider an inhomogeneous generalization of the equation of state considered above and analyse the respective stability regions. In particular, we obtain a specific wormhole solution with an asymptotic behaviour corresponding to a global monopole.

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.

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

Physical Review D, 2005

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.

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...