scholarly journals Phantom fluid supporting traversable wormholes in alternative gravity with extra material terms

2018 ◽  
Vol 27 (16) ◽  
pp. 1950004 ◽  
Author(s):  
P. K. Sahoo ◽  
P. H. R. S. Moraes ◽  
Parbati Sahoo ◽  
G. Ribeiro
Keyword(s):  
State Parameter ◽  
Relativity Theory ◽  
Energy Conditions ◽  
Shape Functions ◽  
General Relativity Theory ◽  
Anisotropic Matter ◽  
Traversable Wormholes ◽  
Geometrical Term ◽  
Alternative Gravity Theory ◽  
Alternative Gravity

Wormholes are tunnels connecting different regions in spacetime. They were obtained originally as a solution for Einstein’s General Relativity theory 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 wormholes within an alternative gravity theory that proposes an extra material (rather than geometrical) term in its gravitational action. Our solutions are obtained from well-known particular cases of the wormhole metric potentials, named redshift and shape functions, and yield the wormholes to be filled by a phantom fluid, that is, a fluid with equation of state parameter [Formula: see text]. In possession of the solutions for the wormhole material content, we also apply the energy conditions to them. The features of those are carefully discussed.

scholarly journals Traversable wormholes in the traceless f(R,T) gravity

2021 ◽  
pp. 2150100
Author(s):  
Parbati Sahoo ◽  
P. H. R. S. Moraes ◽  
Marcelo M. Lapola ◽  
P. K. Sahoo
Keyword(s):  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Shape Functions ◽  
Anisotropic Matter ◽  
Traversable Wormholes ◽  
Theory Of Gravitation ◽  
Geometrical Term

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 energy conditions to them. The features of those are carefully discussed.

scholarly journals Traversable wormholes and energy conditions with two different shape functions in f(R) gravity

2019 ◽  
Vol 28 (02) ◽  
pp. 1950039 ◽  
Author(s):  
Nisha Godani ◽  
Gauranga C. Samanta
Keyword(s):  
Energy Density ◽  
Shape Function ◽  
Energy Condition ◽  
State Parameter ◽  
Null Energy Condition ◽  
Energy Conditions ◽  
Radial Coordinate ◽  
Shape Functions ◽  
Anisotropic Parameter ◽  
Traversable Wormholes

Traversable wormholes, tunnel-like structures introduced by Morris and Thorne [Am. J. Phys. 56 (1988) 395], have a significant role in connection of two different spacetimes or two different parts of the same spacetime. The characteristics of these wormholes depend upon the redshift and shape functions which are defined in terms of radial coordinate. In literature, several shape functions are defined and wormholes are studied in [Formula: see text] gravity with respect to these shape functions [F. S. N. Lobo and M. A. Oliveira, Phys. Rev. D 80 (2009) 104012; H. Saiedi and B. N. Esfahani, Mod. Phys. Lett. A 26 (2011) 1211; S. Bahamonde, M. Jamil, P. Pavlovic and M. Sossich, Phys. Rev. D 94 (2016) 044041]. In this paper, two shape functions (i) [Formula: see text] and (ii) [Formula: see text], [Formula: see text], are considered. The first shape function is newly defined, however, the second one is collected from the literature [M. Cataldo, L. Liempi and P. Rodríguez, Eur. Phys. J. C 77 (2017) 748]. The wormholes are investigated for each type of shape function in [Formula: see text] gravity with [Formula: see text], where [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] are real constants. Varying the parameter [Formula: see text] or [Formula: see text], [Formula: see text] model is studied in five subcases for each type of shape function. In each case, the energy density, radial and tangential pressures, energy conditions that include null energy condition, weak energy condition, strong energy condition and dominated energy condition and anisotropic parameter are computed. The energy density is found to be positive and all energy conditions are obtained to be violated which support the existence of wormholes. Also, the equation-of-state parameter is obtained to possess values less than [Formula: see text], that shows the presence of the phantom fluid and leads toward the expansion of the universe.

scholarly journals Non violation of energy conditions in wormholes modeling

2019 ◽  
Vol 34 (28) ◽  
pp. 1950226 ◽  
Author(s):  
Nisha Godani ◽  
Gauranga C. Samanta
Keyword(s):  
Equation Of State ◽  
Shape Function ◽  
State Parameter ◽  
Energy Conditions ◽  
Shape Functions ◽  
Anisotropic Parameter ◽  
Geometrical Properties ◽  
Traversable Wormholes ◽  
Equation Of State Parameter ◽  
Different Types

Morris and Thorne [M. S. Morris and K. S. Thorne, Am. J. Phys. 56, 395 (1988)] proposed geometrical objects called traversable wormholes that act as bridges in connecting two spacetimes or two different points of the same spacetime. The geometrical properties of these wormholes depend upon the choice of the shape function. In the literature, these are studied in modified gravities for different types of shape functions. In this paper, the traversable wormholes having shape function [Formula: see text] are explored in [Formula: see text] gravity with [Formula: see text], where [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] are real constants. For different values of constants in function [Formula: see text], the analysis is done in various cases. In each case, the energy conditions, equation of state parameter and anisotropic parameter are determined.

Wormhole solutions in modified f(R,φ,X) gravity

2021 ◽  
Vol 36 (04) ◽  
pp. 2150021
Author(s):  
M. Farasat Shamir ◽  
Adnan Malik ◽  
G. Mustafa
Keyword(s):  
Shape Function ◽  
Scalar Potential ◽  
Three Dimensional ◽  
State Parameter ◽  
Energy Conditions ◽  
Kinetic Term ◽  
Anisotropic Fluid ◽  
Shape Functions ◽  
Current Analysis ◽  
Static Space

This work aims to investigate the wormhole solutions in the background of [Formula: see text] theory of gravity, where [Formula: see text] is Ricci scalar, [Formula: see text] is scalar potential, and [Formula: see text] is the kinetic term. We consider spherically symmetric static space–time for exploring the wormhole geometry with anisotropic fluid. For our current analysis, we consider a particular equation of state parameter to study the behavior of traceless fluid and examine the physical behavior of energy density and pressure components. Furthermore, we also choose a particular shape function and explore the energy conditions. It can be noticed that energy conditions are violated for both shape functions. The violation of energy conditions indicates the existence of exotic matter and wormhole. Therefore, it can be concluded that our results are stable and realistic. The interesting feature of this work is to show two- and three-dimensional plotting for the analysis of wormhole geometry.

Two different shape functions for wormholes in f(R) theory with non-commutative geometry and Lorentzian distribution

2020 ◽  
Vol 17 (11) ◽  
pp. 2050155
Author(s):  
Ambuj Kumar Mishra ◽  
Vipin Chandra Dubey ◽  
Umesh Kumar Sharma
Keyword(s):  
General Relativity ◽  
Shape Function ◽  
Anisotropy Parameter ◽  
Point Of View ◽  
Energy Conditions ◽  
Shape Functions ◽  
Throat Radius ◽  
Eos Parameter ◽  
Traversable Wormholes ◽  
Modified Formula

In this work, the solutions of traversable wormholes are investigated inside modified [Formula: see text] gravity under non-commutative geometry since matter possesses Lorentzian density distribution of a particle-like gravitation source. To find the exact wormhole solutions, two different shape functions [Formula: see text], [Formula: see text], and [Formula: see text], [Formula: see text], are considered. The first shape function was proposed by Mishra and Sharma [A new shape function for wormholes in [Formula: see text] gravity and General Relativity, preprint (2020), arXiv:2003.00298v1 [physics.gen-ph]], however the second is newly defined in this paper. The behaviors of both shape functions are analyzed with the throat radius [Formula: see text]. The equation-of-state (EoS) parameter energy conditions, and anisotropy parameter are discussed with graphical point of view.

Static spherically symmetric solutions in f(G) gravity

2016 ◽  
Vol 25 (07) ◽  
pp. 1650083 ◽  
Author(s):  
M. Sharif ◽  
H. Ismat Fatima
Keyword(s):  
Equation Of State ◽  
State Parameter ◽  
Energy Conditions ◽  
Conformal Killing ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Anisotropic Matter ◽  
Physical Validity ◽  
Spherically Symmetric Metric ◽  
Anisotropic Case

We investigate interior solutions for static spherically symmetric metric in the background of [Formula: see text] gravity. We use the technique of conformal Killing motions to solve the field equations with both isotropic and anisotropic matter distributions. These solutions are then used to obtain density, radial and tangential pressures for power-law [Formula: see text] model. For anisotropic case, we assume a linear equation-of-state and investigate solutions for the equation-of-state parameter [Formula: see text]. We check physical validity of the solutions through energy conditions and also examine its stability. Finally, we study equilibrium configuration using Tolman–Oppenheimer–Volkoff equation.

Existence of dynamical wormholes in f(R) gravity

2020 ◽  
Vol 98 (5) ◽  
pp. 474-483
Author(s):  
Z. Yousaf ◽  
A. Ikram ◽  
M. Ilyas ◽  
M.Z. Bhatti
Keyword(s):  
Graphical Analysis ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Shape Functions ◽  
Field Equations ◽  
Ordinary Matter ◽  
Traversable Wormhole ◽  
Traversable Wormholes ◽  
Fluid Configuration

This paper explores spherically symmetrical dynamical traversable wormhole solutions for an anisotropic fluid configuration in the context of f(R) gravity. We construct the corresponding field equations and investigate the wormhole solutions by specifying the redshift and shape functions for three models of f(R) gravity. Graphical analysis shows that ordinary matter satisfies the null as well as weak energy conditions against the time and radial coordinates for each model. It is concluded that dynamical traversable wormholes are supported by this theory.

scholarly journals Some specific wormhole solutions in f(R)-modified gravity theory

2021 ◽  
pp. 2150024
Author(s):  
Bikram Ghosh ◽  
Saugata Mitra ◽  
Subenoy Chakraborty
Keyword(s):  
Modified Gravity ◽  
Shape Function ◽  
Matter Field ◽  
Gravity Theory ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Shape Functions ◽  
Matter Distribution ◽  
Anisotropic Matter ◽  
Modified Gravity Theory

The paper deals with the static spherically symmetric wormhole solutions in [Formula: see text]-modified gravity theory with anisotropic matter field and for some particular choices for the shape functions. This work may be considered as an extension of the general formalism in [S. Halder, S. Bhattacharya and S. Chakraborty, Phys. Lett. B 791, 270 (2019)] for finding wormhole solutions. For isotropic matter distribution it has been shown that wormhole solutions are possible for zero tidal force and it modifies the claim in [M. Cataldo, L. Leimpi and P. Rodriguez, Phys. Lett. B 757, 130 (2016)]. Finally, energy conditions are examined and it is found that all energy conditions are satisfied in a particular domain with a particular choice of the shape function.

Spherically symmetric static wormhole models in the Einsteinian cubic gravity

2020 ◽  
Vol 17 (14) ◽  
pp. 2050214
Author(s):  
G. Mustafa ◽  
Tie-Cheng Xia ◽  
Ibrar Hussain ◽  
M. Farasat Shamir
Keyword(s):  
Shape Function ◽  
Necessary Conditions ◽  
General Relation ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Shape Functions ◽  
Anisotropic Matter ◽  
Lorentzian Signature ◽  
Fields Equations

Our aim is to discuss spherically symmetric static wormholes with the Lorentzian signature in the Einsteinian cubic gravity for two different models of pressure sources. First, we calculate the modified fields equations for the Einsteinian cubic gravity for the wormhole geometry under the anisotropic matter. Then we investigate the shape-function for two different models, which can be taken as a part of the general relation, namely, [Formula: see text]. We further study the energy conditions for both the models in the background of the Einsteinian cubic gravity. We show that our obtained shape-functions satisfy all the necessary conditions for the existence of wormhole solutions in the Einsteinian cubic gravity for some particular values of the different involved parameters. We also discuss the behavior of the energy conditions especially the null and the weak energy conditions for the wormhole models in the Einsteinian cubic gravity.

scholarly journals BIANCHI I SOLUTIONS OF EFFECTIVE QUADRATIC GRAVITY

2012 ◽  
Vol 21 (04) ◽  
pp. 1250037 ◽  
Author(s):  
DANIEL MÜLLER ◽  
JULIANO A. DE DEUS
Keyword(s):  
Numerical Solutions ◽  
Relativity Theory ◽  
De Sitter ◽  
General Relativity Theory ◽  
Spatial Metrics ◽  
Effective Gravity ◽  
Bianchi I ◽  
Quadratic Theory ◽  
Quadratic Gravity ◽  
Planck Time

It is believed that soon after the Planck time, Einstein's general relativity theory should be corrected to an effective quadratic theory. Numerical solutions for the anisotropic generalization of the Friedmann "flat" model E3 for this effective gravity are given. It must be emphasized that although numeric, these solutions are exact in the sense that they depend only on the precision of the machine. The solutions are identified asymptotically in a certain sense. It is found solutions which asymptote de Sitter space, Minkowski space and a singularity. This work is a generalization for nondiagonal spatial metrics of a previous result obtained by one of us and a collaborator for Bianchi I spaces.

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