scholarly journals New traversable wormhole solutions in f(T) gravity

2019 ◽  
Vol 28 (04) ◽  
pp. 1950065 ◽  
Author(s):  
R. C. Tefo ◽  
P. H. Logbo ◽  
M. J. S. Houndjo ◽  
J. Tossa
Keyword(s):  
Time Dependence ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Traversable Wormhole ◽  
Torsion Scalar ◽  
Teleparallel Theory ◽  
Text Model ◽  
Spacetime Metric ◽  
Theory Of Gravity ◽  
Modified Formula

In this paper, we search for dynamical traversable wormhole solutions in the modified [Formula: see text] theory of gravity, [Formula: see text] being the torsion scalar. For such a wormhole, the time dependence is inserted in the static traversable wormhole metric of Morris and Thorne. Two set of tetrads are adopted: the diagonal and the nondiagonal tetrads. The diagonal set of tetrads constrains and reduces [Formula: see text] model to teleparallel theory where usual solutions have been found. With diagonal set of tetrads, free from the teleparallel theory constraint, our results show that the existence of traversable wormhole is possible only for nondynamical spacetime metric, i.e. static traversable wormhole solutions. Moreover we take into account energy condition analysis and the results show that the violation of null energy condition is not determinant for existence of static traversable wormhole solutions.

scholarly journals Traversable wormhole in logarithmic f(R) gravity by various shape and redshift functions

2022 ◽  
Author(s):  
Jafar Sadeghi ◽  
Mehdi Shokri ◽  
Saeed Noori Gashti ◽  
Behnam Pourhassan ◽  
Prabir Rudra
Keyword(s):  
Energy Condition ◽  
Radial Pressure ◽  
Null Energy Condition ◽  
Energy Conditions ◽  
Dominant Energy Condition ◽  
Tangential Pressure ◽  
Strong Energy Condition ◽  
Traversable Wormhole ◽  
Strong Energy ◽  
Text Model

In this paper, we study the traversable wormhole solutions for a logarithmic corrected [Formula: see text] model by considering two different statements of shape [Formula: see text] and redshift [Formula: see text] functions. We calculate the parameters of the model including energy density [Formula: see text], tangential pressure [Formula: see text] and radial pressure [Formula: see text] for the corresponding forms of the functions. Then, we investigate different energy conditions such as null energy condition, weak energy condition, dominant energy condition and strong energy condition for our considered cases. Finally, we explain the satisfactory conditions of energy of the models by related plots.

TIME MACHINE AT THE LHC

2008 ◽  
Vol 05 (04) ◽  
pp. 641-651 ◽  
Author(s):  
I. YA. AREF'EVA ◽  
I. V. VOLOVICH
Keyword(s):  
Black Hole ◽  
Cross Section ◽  
Production Cross ◽  
Hadron Collider ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Time Machine ◽  
Proton Proton ◽  
Traversable Wormhole ◽  
Time Machines

Recently, black hole and brane production at CERN's Large Hadron Collider (LHC) has been widely discussed. We suggest that there is a possibility to test causality at the LHC. We argue that if the scale of quantum gravity is of the order of few TeVs, proton-proton collisions at the LHC could lead to the formation of time machines (spacetime regions with closed timelike curves) which violate causality. One model for the time machine is a traversable wormhole. We argue that the traversable wormhole production cross section at the LHC is of the same order as the cross section for the black hole production. Traversable wormholes assume violation of the null energy condition (NEC) and an exotic matter similar to the dark energy is required. Decay of the wormholes/time machines and signatures of time machine events at the LHC are discussed.

Wormhole solutions via embedding approach in ℛ + βℛ2 gravity with matter coupling

2021 ◽  
Author(s):  
Dan Wang ◽  
G. Mustafa
Keyword(s):  
Shape Function ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Specific Model ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Modified Theories Of Gravity ◽  
Class 1 ◽  
Theory Of Gravity ◽  
Feasible Solutions

In this paper, we examine the embedded wormhole solutions in the modified [Formula: see text] theory of gravity, where [Formula: see text] denotes the trace of the energy–momentum tensor and [Formula: see text] is the Ricci scalar. We derive the embedded class-1 solutions by considering spherically symmetric static spacetime. The shape function is calculated in the framework of embedded class-1 spacetime. It is necessary to mention here that the calculated shape function can be used in other modified theories of gravity. We explore the feasible solutions for the specific model of [Formula: see text] theory of gravity. Energy conditions have been explored using the approach mentioned above. Conclusively, we find that obtained wormhole solutions are acceptable, as the null energy condition is violated in the specific region.

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.

Mesonic tilted cosmological model with wet dark fluid in F(T) theory of gravity

2020 ◽  
Vol 98 (7) ◽  
pp. 636-642 ◽  
Author(s):  
V.J. Dagwal
Keyword(s):  
Heat Conduction ◽  
Cosmological Model ◽  
Tilt Angle ◽  
Cosmological Models ◽  
Wet Dark Fluid ◽  
Torsion Scalar ◽  
Dark Fluid ◽  
Tilted Cosmological Model ◽  
Teleparallel Theory ◽  
Theory Of Gravity

This study presents mesonic tilted cosmological models with wet dark fluid in the F(T) theory of gravity, which is an extension of the Teleparallel theory of gravity, where T is the torsion scalar. In this paper, a new idea is introduced about the F(T) theory of gravity with the help of tilt angle, heat conduction, and mesonic wet dark fluid. The cosmological evolution in F(T) models is investigated. The physical and geometrical aspects of the models are also discussed.

scholarly journals On the existence and stability of traversable wormhole solutions in modified theories of gravity

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
Oleksii Sokoliuk ◽  
Alexander Baransky
Keyword(s):  
Shape Function ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Modified Theories Of Gravity ◽  
Energy Tensor ◽  
Field Equations ◽  
Traversable Wormhole ◽  
Existence And Stability ◽  
Theories Of Gravity ◽  
The Stability

AbstractWe study Morris–Thorne static traversable wormhole solutions in different modified theories of gravity. We focus our study on the quadratic gravity $$f({\mathscr {R}}) = {\mathscr {R}}+a{\mathscr {R}}^2$$ f ( R ) = R + a R 2 , power-law $$f({\mathscr {R}}) = f_0{\mathscr {R}}^n$$ f ( R ) = f 0 R n , log-corrected $$f({\mathscr {R}})={\mathscr {R}}+\alpha {\mathscr {R}}^2+\beta {\mathscr {R}}^2\ln \beta {\mathscr {R}}$$ f ( R ) = R + α R 2 + β R 2 ln β R theories, and finally on the exponential hybrid metric-Palatini gravity $$f(\mathscr {\hat{R}})=\zeta \bigg (1+e^{-\frac{\hat{{\mathscr {R}}}}{\varPhi }}\bigg )$$ f ( R ^ ) = ζ ( 1 + e - R ^ Φ ) . Wormhole fluid near the throat is adopted to be anisotropic, and redshift factor to have a constant value. We solve numerically the Einstein field equations and we derive the suitable shape function for each MOG of our consideration by applying the equation of state $$p_t=\omega \rho $$ p t = ω ρ . Furthermore, we investigate the null energy condition, the weak energy condition, and the strong energy condition with the suitable shape function b(r). The stability of Morris–Thorne traversable wormholes in different modified gravity theories is also analyzed in our paper with a modified Tolman–Oppenheimer–Voklov equation. Besides, we have derived general formulas for the extra force that is present in MTOV due to the non-conserved stress-energy tensor.

scholarly journals Phantom fluid wormhole in f(R, T) gravity

2019 ◽  
Vol 34 (37) ◽  
pp. 1950303 ◽  
Author(s):  
Parbati Sahoo ◽  
Annika Kirschner ◽  
P. K. Sahoo
Keyword(s):  
Modified Gravity ◽  
Energy Condition ◽  
Phantom Energy ◽  
Null Energy Condition ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Phantom Dark Energy ◽  
Modified Gravity Theories ◽  
De Formula ◽  
Modified Formula

Wormholes (WHs) are considered as hypothetical shortcuts or tunnels in spacetime. In general relativity (GR), the fundamental ingredient of WH geometry is the presence of exotic matter at the throat, which is responsible for the violation of null energy condition (NEC). However, the modified gravity theories have shown to be able to provide WH solutions satisfying energy conditions (ECs). In this paper, we study the static spherically symmetric WH solutions in modified [Formula: see text] gravity for a phantom fluid case. The exact solutions of this model are obtained through the equation of state (EoS), [Formula: see text], associated with phantom dark energy (DE) [Formula: see text]. We find the existence of spherically symmetric WH solution supported by phantom energy distribution. The shape function of the WH obtained in this model obeys all the WH metric conditions. In modified gravity scenario, the phantom fluid WH violates the NEC in radial case, unlike in the tangential case. Furthermore, using the “volume integral quantifier” (VIQ) method, the total amount of EC violating matter in spacetime is discussed briefly.

scholarly journals Existence of static wormholes in f(𝒢,T) gravity

2017 ◽  
Vol 27 (01) ◽  
pp. 1750182 ◽  
Author(s):  
M. Sharif ◽  
Ayesha Ikram
Keyword(s):  
Energy Momentum Tensor ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Graphical Analysis ◽  
Momentum Tensor ◽  
Specific Form ◽  
Spherically Symmetric ◽  
Matter Distribution ◽  
Ordinary Matter ◽  
Text Model

This paper investigates static spherically symmetric traversable wormhole (WH) solutions in [Formula: see text] gravity ([Formula: see text] and [Formula: see text] represent the Gauss–Bonnet invariant and trace of the energy–momentum tensor, respectively). We construct explicit expressions for ordinary matter by taking specific form of redshift function and [Formula: see text] model. To analyze the possible existence of wormholes, we consider anisotropic, isotropic, as well as barotropic matter distributions. The graphical analysis shows the violation of null energy condition for the effective energy–momentum tensor throughout the evolution while ordinary matter meets energy constraints in certain regions for each case of matter distribution. It is concluded that traversable WH solutions are physically acceptable in this theory.

Two-fluid sources in F (T ) theory of gravity

2019 ◽  
Vol 35 (04) ◽  
pp. 1950357 ◽  
Author(s):  
V. J. Dagwal ◽  
D. D. Pawar
Keyword(s):  
Matter Field ◽  
Microwave Background ◽  
Two Fluids ◽  
Field Modeling ◽  
Modeling Material ◽  
Teleparallel Theory ◽  
Text Model ◽  
Theory Of Gravity ◽  
The Universe ◽  
Two Fluid

We have investigated two-fluid cosmological models in [Formula: see text] theory of gravity. [Formula: see text] theory is an extension of teleparallel theory of gravity, where [Formula: see text] is the torsion scalar. In this paper, we formulated new idea about [Formula: see text] theory of gravity with the help of two fluids: one fluid is matter field modeling material content of the Universe and another fluid is radiation field modeling the cosmic microwave background. Some geometric aspects of the [Formula: see text] model are discussed with the help of MATLAB.

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.

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