Spherically symmetric traversable wormholes in f(R2,T) gravity

2019 ◽  
Vol 16 (10) ◽  
pp. 1950147 ◽  
Author(s):  
M. Zubair ◽  
Quratulien Muneer ◽  
Saira Waheed
Keyword(s):  
Modified Gravity ◽  
Arbitrary Constant ◽  
Energy Momentum Tensor ◽  
Energy Condition ◽  
Momentum Tensor ◽  
Anisotropic Fluid ◽  
Spherically Symmetric ◽  
Matter Distribution ◽  
Field Equations ◽  
Traversable Wormholes

In this paper, we explore the possibility of wormhole solutions existence exhibiting spherical symmetry in an interesting modified gravity based on Ricci scalar term and trace of energy–momentum tensor. For this reason, we assume the matter distribution as anisotropic fluid and a specific viable form of the generic function given by [Formula: see text] involving [Formula: see text] and [Formula: see text], two arbitrary constant parameters. For having a simplified form of the resulting field equations, we assume three different forms of EoS of the assumed matter contents. In each case, we find the numerical wormhole solutions and analyze their properties for the wormhole existence graphically. The graphical behavior of the energy condition bounds is also investigated in each case. It is found that a realistic wormhole solutions satisfying all the properties can be obtained in each case.

Spherically symmetric spacetime with radiating fluids in f(𝒢, T) gravity

2019 ◽  
Vol 34 (27) ◽  
pp. 1950215 ◽  
Author(s):  
M. Farasat Shamir ◽  
Nabeeha Uzair
Keyword(s):  
Weyl Tensor ◽  
Energy Momentum Tensor ◽  
Stellar System ◽  
Momentum Tensor ◽  
Anisotropic Fluid ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Radiating Fluids ◽  
Inhomogeneity Factor ◽  
Symmetric Spacetime

The aim of this paper is to examine the irregularity factors of a self-gravitating stellar system in the existence of anisotropic fluid. We investigate the dynamics of field equations within [Formula: see text] background, where [Formula: see text] is the Gauss–Bonnet invariant and [Formula: see text] is the trace of the energy–momentum tensor. Moreover, we have investigated two differential equations using the conservation law and the Weyl tensor. We have determined the irregularity factors of spherical stellar system for some specific conditions of anisotropic and isotropic fluids, dust, radiating and non-radiating systems in [Formula: see text] gravity. It has been noted that the dissipative matter results in anisotropic stresses and makes the system more complex. The inhomogeneity factor is correlated to one of the scalar functions.

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.

Study of gravitational decoupled anisotropic solution

2019 ◽  
Vol 28 (16) ◽  
pp. 2040004
Author(s):  
M. Sharif ◽  
Sobia Sadiq
Keyword(s):  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Anisotropic Model ◽  
Field Equations ◽  
Anisotropic Solution ◽  
Spherically Symmetric Solution ◽  
Gravitational Source ◽  
The Stability

This paper formulates the exact static anisotropic spherically symmetric solution of the field equations through gravitational decoupling. To accomplish this work, we add a new gravitational source in the energy–momentum tensor of a perfect fluid. The corresponding field equations, hydrostatic equilibrium equation as well as matching conditions are evaluated. We obtain the anisotropic model by extending the known Durgapal and Gehlot isotropic solution and examined the physical viability as well as the stability of the developed model. It is found that the system exhibits viable behavior for all fluid variables as well as energy conditions and the stability criterion is fulfilled.

scholarly journals ON THE NATURAL GAUGE FIELDS OF MANIFOLDS

2000 ◽  
Vol 15 (32) ◽  
pp. 1991-2005 ◽  
Author(s):  
A. B. PESTOV ◽  
BIJAN SAHA
Keyword(s):  
Displacement Field ◽  
Energy Momentum Tensor ◽  
Linear Connection ◽  
Momentum Tensor ◽  
Gauge Fields ◽  
Spherically Symmetric ◽  
Time Inversion ◽  
Field Equations ◽  
Gauge Invariant ◽  
Minkowski Space Time

The gauge symmetry inherent in the concept of manifold has been discussed. Within the scope of this symmetry the linear connection or displacement field can be considered as a natural gauge field on the manifold. The gauge-invariant equations for the displacement field have been derived. It has been shown that the energy–momentum tensor of this field conserves and hence the displacement field can be treated as one that transports energy and gravitates. To show the existence of the solutions of the field equations, we have derived the general form of the displacement field in Minkowski space–time which is invariant under rotation and space and time inversion. With this ansatz we found spherically-symmetric solutions of the equations in question.

Energy conditions and modified gravity in anisotropic universe

2018 ◽  
Vol 96 (2) ◽  
pp. 225-232 ◽  
Author(s):  
H. Hossienkhani ◽  
V. Fayaz ◽  
A. Jafari
Keyword(s):  
Modified Gravity ◽  
General Scheme ◽  
Energy Condition ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Anisotropic Universe ◽  
Type I ◽  
De Sitter ◽  
Field Equations ◽  
New Formula

In this paper, energy conditions in a new [Formula: see text] modified gravity ([Formula: see text] and T represent the Gauss–Bonnet invariant and trace of the energy–momentum tensor, respectively) for anisotropic universe with perfect fluid are analyzed. In this model, we develop the general scheme for new [Formula: see text] modified gravity reconstruction from realistic anisotropic Bianchi type-I cosmology. Using de Sitter solution, the exact solutions of the field equations have been obtained. It is found that null and weak energy conditions are satisfied for the parameter range considered. As a result, the analyses show that the increase of anisotropy is attributed to the increase of weak energy condition.

scholarly journals Exploring cylindrical solutions in modified f(G) gravity

2014 ◽  
Vol 92 (12) ◽  
pp. 1528-1540 ◽  
Author(s):  
M.J.S. Houndjo ◽  
M.E. Rodrigues ◽  
D. Momeni ◽  
R. Myrzakulov
Keyword(s):  
Exact Solutions ◽  
Energy Momentum Tensor ◽  
Unit Length ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Momentum Tensor ◽  
Field Equations ◽  
Full System ◽  
Bonnet Gravity ◽  
Cylindrically Symmetric

We present detailed cylindrically symmetric solutions for a type of Gauss–Bonnet gravity. We derive the full system of field equations and show that there exist seven families of exact solutions for three forms of viable models. By applying the method based on the effective fluid energy momentum tensor components, we evaluate the mass per unit length for the solutions. From a dynamical point of the view, by evaluating the null energy condition for these configurations, we show that in some cases the azimuthal pressure breaks the energy condition. This violation of the null energy condition predicts the existence of a cylindrical wormhole.

Cosmic evolution in the background of R (1 + αQ) gravity

2019 ◽  
Vol 34 (31) ◽  
pp. 1950253 ◽  
Author(s):  
M. Zubair ◽  
M. Zeeshan ◽  
Saira Waheed
Keyword(s):  
Energy Momentum Tensor ◽  
Energy Condition ◽  
Momentum Tensor ◽  
Model Parameters ◽  
Field Equations ◽  
Cosmic Evolution ◽  
Test Particles ◽  
Free Model ◽  
Free Parameters ◽  
Modified Theory

In this paper, we discuss the cosmic evolution in a modified theory involving non-minimal interaction of geometry and matter, labeled as [Formula: see text] gravity, where [Formula: see text] is the non-minimal interaction term. First, we develop the dynamical [Formula: see text] field equations for Friedmann–Lemaitre–Robertson–Walker (FLRW) spacetime and then by using divergence of these equations, we explore its interesting outcome of non-conserved energy–momentum tensor (EMT). The presence of geometry matter coupling in such theories results in non-geodesic test particles motion and hence causes an additional force orthogonal to four-velocity of these particles. By taking these interesting features into account along with a particular choice of Lagrangian [Formula: see text], we explore the resulting expression of energy density. Further, the free model parameters are constrained using energy condition bounds where it is concluded that these values of free parameters are compatible with the recent data.

Galactic halo traversable wormhole solutions in f(𝒢,T) gravity

2018 ◽  
Vol 27 (16) ◽  
pp. 1950009 ◽  
Author(s):  
M. Sharif ◽  
Ayesha Ikram
Keyword(s):  
Galactic Halo ◽  
Shape Function ◽  
Energy Momentum Tensor ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Momentum Tensor ◽  
Specific Form ◽  
Spherically Symmetric ◽  
Effective Energy ◽  
Text Model

This paper explores static spherically symmetric wormhole solutions in the galatic halo region for [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 formulate the explicit expressions for matter variables and evaluate wormhole solutions either specifying [Formula: see text] model to construct shape function or taking specific form of the shape function to determine [Formula: see text] model. It is found that null energy condition for the effective energy–momentum tensor is violated throughout the evolution in both cases while physically acceptable wormhole solutions exist only for a considered [Formula: see text] model.

scholarly journals Galactic Halo Wormhole Solutions inf(T)Gravity

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
M. Sharif ◽  
Shamaila Rani
Keyword(s):  
Galactic Halo ◽  
Energy Momentum Tensor ◽  
Energy Condition ◽  
Teleparallel Gravity ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Stable Configuration ◽  
Spherically Symmetric ◽  
Effective Energy ◽  
Normal Matter

The proposal of galactic halo region is based on the idea that dark halos contain some characteristics needed to support traversable wormhole solutions. We explore wormhole solutions in this region in the framework of generalized teleparallel gravity. We consider static spherically symmetric wormhole spacetime with flat galactic rotational curves and obtain expressions of matter components for nondiagonal tetrad. The effective energy-momentum tensor leads to the violation of energy conditions which may impose condition on the normal matter to satisfy these conditions. We take two well-knownf(T)models in exponential and logarithmic forms to discuss wormhole solutions as well as the equilibrium condition. It is concluded that wormhole solutions violating weak energy condition are obtained for both models with stable configuration.

scholarly journals PECULIAR ANISOTROPIC STATIONARY SPHERICALLY SYMMETRIC SOLUTION OF EINSTEIN EQUATIONS

2012 ◽  
Vol 27 (09) ◽  
pp. 1250044 ◽  
Author(s):  
EMANUEL GALLO ◽  
OSVALDO M. MORESCHI
Keyword(s):  
Dark Matter ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Einstein Equations ◽  
Spherically Symmetric ◽  
Gravitational Lenses ◽  
Field Equations ◽  
Spherically Symmetric Solution ◽  
Stress Energy ◽  
Stress Energy Momentum Tensor

Motivated by studies on gravitational lenses, we present an exact solution of the field equations of general relativity, which is static and spherically symmetric, has no mass but has a nonvanishing spacelike components of the stress–energy–momentum tensor. In spite of its strange nature, this solution has nontrivial descriptions of gravitational effects. We show that the main aspects found in the dark matter phenomena can be satisfactorily described by this geometry. We comment on the relevance it could have to consider nonvanishing spacelike components of the stress–energy–momentum tensor ascribed to dark matter.

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