Influence of modification of gravity on spherical wormhole models

2017 ◽  
Vol 32 (30) ◽  
pp. 1750163 ◽  
Author(s):  
Z. Yousaf ◽  
M. Ilyas ◽  
M. Z. Bhatti
Keyword(s):  
Equation Of State ◽  
Gravity Model ◽  
Modified Gravity ◽  
Shape Function ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Barotropic Equation ◽  
The Stability

This paper explores some wormhole (WH) solutions in the background of additional matter contents of f(R, T) modified gravity. For this purpose, we have considered WH geometry filled with two physically different fluid configurations: one is anisotropic and another is anisotropic characterized by the barotropic equation of state. The energy conditions are examined with particular modified gravity model and found the existence of WH solutions even in the absence of exotic matter. Also, we have analyzed the behavior of shape function in this framework. The stability and physical existence of these solutions is studied with different fluid configurations. We conclude that in the absence of exotic matter, one can find WH solutions with particular model of modified gravity.

Stable Morris Thorne wormholes supported by non-exotic matter

2021 ◽  
pp. 2150170
Author(s):  
Nisha Godani
Keyword(s):  
General Relativity ◽  
Gravity Model ◽  
Stability Condition ◽  
Modified Gravity ◽  
Shape Function ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Traversable Wormholes ◽  
The Stability ◽  
Metric Function

The present work is focused on the study of traversable wormholes, proposed by Morris and Thorne [Wormholes in spacetime and their use for interstellar travel: A tool for teaching general relativity, Am. J. Phys. 56 (1988) 395], using the background of modified gravity. It is performed by using the models: I. [Formula: see text], II. [Formula: see text] and III. [Formula: see text], where [Formula: see text], [Formula: see text] and [Formula: see text] are constants. The Model I belongs to the theory of [Formula: see text] gravity, Model II belongs to the theory of [Formula: see text] gravity and Model III is a combination of Models I and II. These functions have been taken into account for the exploration of wormhole solutions. The shape function, a wormhole metric function, is newly defined which satisfies the flare out condition. Further, the stability condition and energy conditions, namely null, weak and dominant energy conditions, have been examined with respect to each model.

scholarly journals Traversable wormholes with exponential shape function in modified gravity and general relativity: A comparative study

2020 ◽  
Vol 29 (09) ◽  
pp. 2050068 ◽  
Author(s):  
Gauranga C. Samanta ◽  
Nisha Godani ◽  
Kazuharu Bamba
Keyword(s):  
General Relativity ◽  
Equation Of State ◽  
Comparative Study ◽  
Modified Gravity ◽  
Shape Function ◽  
Anisotropy Parameter ◽  
Energy Conditions ◽  
Traversable Wormholes

We have proposed a novel shape function on which the metric that models traversable wormholes is dependent. Using this shape function, the energy conditions, equation-of-state and anisotropy parameter are analyzed in [Formula: see text] gravity, [Formula: see text] gravity and general relativity. Furthermore, the consequences obtained with respect to these theories are compared. In addition, the existence of wormhole geometries is investigated.

scholarly journals Dynamic wormhole geometries in hybrid metric-Palatini gravity

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Mahdi Kord Zangeneh ◽  
Francisco S. N. Lobo
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Shape Function ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Time Dependent ◽  
Energy Conditions ◽  
Tensor Representation ◽  
Traversable Wormhole ◽  
Barotropic Equation

AbstractIn this work, we analyse the evolution of time-dependent traversable wormhole geometries in a Friedmann–Lemaître–Robertson–Walker background in the context of the scalar–tensor representation of hybrid metric-Palatini gravity. We deduce the energy–momentum profile of the matter threading the wormhole spacetime in terms of the background quantities, the scalar field, the scale factor and the shape function, and find specific wormhole solutions by considering a barotropic equation of state for the background matter. We find that particular cases satisfy the null and weak energy conditions for all times. In addition to the barotropic equation of state, we also explore a specific evolving wormhole spacetime, by imposing a traceless energy–momentum tensor for the matter threading the wormhole and find that this geometry also satisfies the null and weak energy conditions at all times.

Stability of charged Kiselev thin-shell wormholes

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040015
Author(s):  
Muhammad Sharif ◽  
Faisal Javed
Keyword(s):  
Black Holes ◽  
Equation Of State ◽  
Thin Shell ◽  
Unstable Behavior ◽  
Wormhole Throat ◽  
Barotropic Equation ◽  
Thin Shell Wormholes ◽  
The Stability

This work is devoted to exploring the stability of thin-shell wormholes developed from two equivalent copies of charged quintessence (charged Kiselev) black holes by using Visser cut and paste approach. The characteristics of the surface matter of the shell are determined by using Israel formalism. We examine the stability of thin-shell by assuming a barotropic equation of state for the surface matter of the wormhole throat. We conclude that wormhole becomes stable in the presence of both charge and Kiselev parameter otherwise, it shows an unstable behavior.

Exact wormholes solutions without exotic matter in f(R,T) gravity

2019 ◽  
Vol 16 (03) ◽  
pp. 1950046 ◽  
Author(s):  
M. Zubair ◽  
Rabia Saleem ◽  
Yasir Ahmad ◽  
G. Abbas
Keyword(s):  
Momentum Tensor ◽  
Exotic Matter ◽  
Gravity Models ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Energy Tensor ◽  
Field Equations ◽  
Stress Energy ◽  
Symmetric Geometry ◽  
The Stability

This paper is aimed to evaluate the existence of wormholes in viable [Formula: see text] gravity models (where [Formula: see text] is the scalar curvature and [Formula: see text] is the trace of stress–energy tensor of matter). The exact solutions for energy–momentum tensor components depending on different shapes and redshift functions are calculated without some additional constraints. To investigate this, we consider static spherically symmetric geometry with matter contents as anisotropic fluid and formulate the Einstein field equations for three different [Formula: see text] models. For each model, we derive expression for weak and null energy conditions and graphically analyzed its violation near the throat. It is really interesting that wormhole solutions do not require the presence of exotic matter — like that in general relativity. Finally, the stability of the solutions for each model is presented using equilibrium condition.

scholarly journals Wormhole modeling in R2 gravity with linear trace term

2020 ◽  
Vol 35 (08) ◽  
pp. 2050045
Author(s):  
Nisha Godani ◽  
Gauranga C. Samanta
Keyword(s):  
General Relativity ◽  
General Theory ◽  
Significant Contribution ◽  
Shape Function ◽  
Exotic Matter ◽  
Geometric Configuration ◽  
Energy Conditions ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Traversable Wormholes

Morris and Thorne1 proposed traversable wormholes, hypothetical connecting tools, using the concept of Einstein’s general theory of relativity. In this paper, the modification of general relativity (in particular [Formula: see text] theory of gravity defined by Harko et al.2) is considered, to study the traversable wormhole solutions. The function [Formula: see text] is considered as [Formula: see text], where [Formula: see text] and [Formula: see text] are controlling parameters. The shape and redshift functions appearing in the metric of wormhole structure have significant contribution in the development of wormhole solutions. We have considered both variable and constant redshift functions with a logarithmic shape function. The energy conditions are examined, geometric configuration is analyzed and the radius of the throat is determined in order to have wormhole solutions in absence of exotic matter.

scholarly journals Lorentz Distributed Noncommutative F(T,TG) Wormhole Solutions

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
M. Sharif ◽  
Kanwal Nazir
Keyword(s):  
Equilibrium Condition ◽  
Shape Function ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Torsion Scalar ◽  
Lorentzian Distribution ◽  
The Stability ◽  
Bonnet Term

The aim of this paper is to study static spherically symmetric noncommutative F(T,TG) wormhole solutions along with Lorentzian distribution. Here, T and TG are torsion scalar and teleparallel equivalent Gauss-Bonnet term, respectively. We take a particular redshift function and two F(T,TG) models. We analyze the behavior of shape function and also examine null as well as weak energy conditions graphically. It is concluded that there exist realistic wormhole solutions for both models. We also studied the stability of these wormhole solutions through equilibrium condition and found them stable.

Dynamics of thin-shell wormholes with different cosmological models

2017 ◽  
Vol 26 (05) ◽  
pp. 1741007 ◽  
Author(s):  
Muhammad Sharif ◽  
Saadia Mumtaz
Keyword(s):  
Equation Of State ◽  
Electric Charge ◽  
General Equation ◽  
Thin Shell ◽  
Cosmological Models ◽  
Exotic Matter ◽  
Linear Perturbation ◽  
Stability Regions ◽  
Thin Shell Wormholes ◽  
The Stability

This work is devoted to investigate the stability of thin-shell wormholes in Einstein–Hoffmann–Born–Infeld electrodynamics. We also study the attractive and repulsive characteristics of these configurations. A general equation-of-state is considered in the form of linear perturbation which explores the stability of the respective wormhole solutions. We assume Chaplygin, linear and logarithmic gas models to study exotic matter at thin-shell and evaluate stability regions for different values of the involved parameters. It is concluded that the Hoffmann–Born–Infeld parameter and electric charge enhance the stability regions.

Stability of ABG thin-shell around a traversable wormhole

2021 ◽  
pp. 2150044
Author(s):  
M. Sharif ◽  
Komal Ashraf
Keyword(s):  
Thin Shell ◽  
Shape Function ◽  
Energy Conditions ◽  
Energy Tensor ◽  
De Sitter ◽  
Stress Energy Tensor ◽  
Regular Black Hole ◽  
Traversable Wormhole ◽  
Stress Energy ◽  
Barotropic Equation

This paper investigates stability of thin-shell developed from the matching of interior traversable wormhole with exterior Ayon–Beato–Garcia–de Sitter regular black hole through cut and paste approach. We employ Israel formalism and Lanczos equations to obtain the components of surface stress-energy tensor at thin-shell. These surface stresses violate null and weak energy conditions that suggest the presence of exotic matter at thin-shell. The surface pressure explains collapse as well as expanding behavior of the developed geometry. We explore stability of the constructed thin-shell through both perturbations along shell radius as well as barotropic equation of state for three appropriate values of the shape function [Formula: see text]. It is concluded that stability of thin-shell depends on the shape function, charge and cosmological constant.

scholarly journals Charged compact star in f(R, T) gravity in Tolman–Kuchowicz spacetime

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Pramit Rej ◽  
Piyali Bhar ◽  
Megan Govender
Keyword(s):  
Modified Gravity ◽  
Line Element ◽  
Compact Star ◽  
Stellar System ◽  
Radial Pressure ◽  
Energy Conditions ◽  
Field Equations ◽  
Compactness Factor ◽  
Physical Validity ◽  
The Stability

AbstractIn this current study, our main focus is on modeling the specific charged compact star SAX J 1808.4-3658 (M = 0.88 $$M_{\odot }$$ M ⊙ ,  R = 8.9 km) within the framework of $$f(R,\,T)$$ f ( R , T ) modified gravity theory using the metric potentials proposed by Tolman–Kuchowicz (Tolman in Phys Rev 55:364, 1939; Kuchowicz in Acta Phys Pol 33:541, 1968) and the interior spacetime is matched to the exterior Reissner–Nordström line element at the surface of the star. Tolman–Kuchowicz metric potentials provide a singularity-free solution which satisfies the stability criteria. Here we have used the simplified phenomenological MIT bag model equation of state (EoS) to solve the Einstein–Maxwell field equations where the density profile ($$\rho $$ ρ ) is related to the radial pressure ($$p_{\mathrm{r}}$$ p r ) as $$p_{\mathrm{r}}(r) = (\rho - 4B_{\mathrm{g}})/3$$ p r ( r ) = ( ρ - 4 B g ) / 3 . Furthermore, to derive the values of the unknown constants $$a,\, b,\, B,\, C$$ a , b , B , C and the bag constant $$B_{\mathrm{g}}$$ B g , we match our interior spacetime to the exterior Reissner–Nordström line element at the surface of stellar system. In addition, to check the physical validity and stability of our suggested model we evaluate some important properties, such as effective energy density, effective pressures, radial and transverse sound velocities, relativistic adiabatic index, all energy conditions, compactness factor and surface redshift. It is depicted from our current study that all our derived results lie within the physically accepted regime which shows the viability of our present model in the context of $$f(R,\,T)$$ f ( R , T ) modified gravity.

Sign in / Sign up

Export Citation Format

Share Document