Power law f(đť’˘,T) gravity models supporting wormhole solutions

2018 ◽  
Vol 15 (05) ◽  
pp. 1850070 ◽  
Author(s):  
M. Farasat Shamir ◽  
Mushtaq Ahmad
Keyword(s):  
Power Law ◽  
Momentum Tensor ◽  
Matter Content ◽  
Gravity Models ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Ordinary Matter ◽  
Specific Formula ◽  
The Stability ◽  
Modified Formula

This work provides some feasible regions for the existence of traversable wormhole geometries in modified [Formula: see text] gravity. For this purpose, three different matter contents have been studied with special emphasis on anisotropic fluid by considering a specific [Formula: see text] gravity power law model. It has been shown that the null energy conditions for the effective energy–momentum tensor are widely violated for the ordinary matter content. However, some small feasible regions to support the wormhole solutions have been noted. Furthermore, the stability of the anisotropic feasible regions for the wormhole solutions has been discussed. It is concluded that the wormhole geometries threaded by the ordinary matter actually exist and are well stable in [Formula: see text] gravity.

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.

Wormhole models in f(R,T) gravity

2019 ◽  
Vol 28 (15) ◽  
pp. 1950172 ◽  
Author(s):  
Emilio Elizalde ◽  
Martiros Khurshudyan
Keyword(s):  
Energy Momentum Tensor ◽  
Equations Of State ◽  
Energy Condition ◽  
Physical Nature ◽  
Radial Pressure ◽  
Momentum Tensor ◽  
Matter Content ◽  
Energy Conditions ◽  
Dominant Energy Condition ◽  
The Stability

Models of static wormholes within the [Formula: see text] extended theory of gravity are investigated, in particular the family [Formula: see text], with [Formula: see text] being the trace of the energy–momentum tensor. Models corresponding to different relations for the pressure components (radial and lateral), and several equations-of-state (EoS), reflecting different matter content, are worked out explicitly. The solutions obtained for the shape functions of the generated wormholes obey the necessary metric conditions, as manifested in other studies in the literature. The respective energy conditions reveal the physical nature of the wormhole models thus constructed. It is found, in particular, that for each of those considered, the parameter space can be divided into different regions, in which the exact wormhole solutions fulfill the null energy conditions (NEC) and the weak energy conditions (WEC), respectively, in terms of the lateral pressure. Moreover, the dominant energy condition (DEC) in terms of both pressures is also valid, while [Formula: see text]. A similar solution for the theory [Formula: see text] is found numerically, where [Formula: see text] and [Formula: see text] are either constant or functions of [Formula: see text], leading to the result that the NEC in terms of the radial pressure is also valid. For nonconstant [Formula: see text] models, attention is focused on the behavior [Formula: see text]. To finish, the question is addressed, how [Formula: see text] will affect the wormhole solutions corresponding to fluids of the form [Formula: see text], in the three cases such as NEC, WEC and DEC. Issues concerning the nonconservation of the matter energy–momentum tensor, the stability of the solutions obtained, and the observational possibilities for testing these models are discussed in Sec. 6.

scholarly journals Energy conditions in higher derivative f(R,â–ˇR,T) gravity

2018 ◽  
Vol 15 (09) ◽  
pp. 1850146 ◽  
Author(s):  
Z. Yousaf ◽  
M. Sharif ◽  
M. Ilyas ◽  
M. Zaeem-ul-Haq Bhatti
Keyword(s):  
Energy Momentum Tensor ◽  
Energy Condition ◽  
Momentum Tensor ◽  
Matter Content ◽  
Energy Conditions ◽  
Higher Derivative ◽  
Derivative Formula ◽  
Cosmological Solutions ◽  
The Stability ◽  
Cosmic Parameters

In this paper, we examined the viability bounds of a higher derivative [Formula: see text] theory through analyzing energy conditions (where [Formula: see text] and [Formula: see text] are the Ricci scalar, d’Alemberts operator and trace of energy–momentum tensor, respectively). We take flat Friedmann–Lemaître–Robertson–Walker spacetime coupled with ideal configurations of matter content. We consider three different realistic models of this gravity, that could be utilized to understand the stability of cosmological solutions. After constructing certain bounds mediated by energy conditions, more specifically the weak energy condition, we discuss viable zones of the under considered modified models in an environment of recent estimated numerical choices of the cosmic parameters.

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 Some exact solutions in f(đť’˘,T) gravity via Noether symmetries

2017 ◽  
Vol 32 (16) ◽  
pp. 1750086 ◽  
Author(s):  
M. Farasat Shamir ◽  
Mushtaq Ahmad
Keyword(s):  
Exact Solutions ◽  
Momentum Tensor ◽  
Gravity Models ◽  
Noether Symmetry ◽  
Type I ◽  
Conserved Quantities ◽  
Rotationally Symmetric ◽  
Bianchi Type I Universe ◽  
Modified Formula ◽  
Bonnet Term

This paper is devoted to investigate the recently proposed modified Gauss–Bonnet [Formula: see text] gravity, with [Formula: see text], the Gauss–Bonnet term, coupled with [Formula: see text], the trace of energy–momentum tensor. We have used the Noether symmetry methodology to discuss some cosmologically important [Formula: see text] gravity models with anisotropic background. In particular, the Noether symmetry equations for modified [Formula: see text] gravity are reported for locally rotationally symmetric Bianchi type I universe. Explicitly, two models have been proposed to explore the exact solutions and the conserved quantities. It is concluded that the specific models of modified Gauss–Bonnet gravity may be used to reconstruct [Formula: see text]CDM cosmology without involving any cosmological constant.

Wormhole structures and energy conditions in f(â„›) 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.

Wormholes supported by f(đť’˘) gravity

2014 ◽  
Vol 24 (01) ◽  
pp. 1550003 ◽  
Author(s):  
M. Sharif ◽  
Ayesha Ikram
Keyword(s):  
Power Law ◽  
Energy Momentum Tensor ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Momentum Tensor ◽  
Red Shift ◽  
Energy Conditions ◽  
Shift Function ◽  
Effective Energy ◽  
Barotropic Fluids

This paper is devoted to study the traversable wormhole (WH) solutions in the context of f(đť’˘) gravity. For this purpose, we consider the viable power-law form f(đť’˘) = ađť’˘n as well as specific variable red-shift function and investigate WH geometries for traceless, isotropic as well as barotropic fluids. It is found that in each case, the effective energy-momentum tensor violates the null energy condition throughout the WH throat. We also check the null as well as weak energy conditions for ordinary matter. We conclude that physical acceptable WH solutions exist in certain regions only for radial barotropic case while the range of these regions increases and decreases as the power of đť’˘ increases in even and odd manner, respectively.

scholarly journals FAMILY OF ROTATING ANISOTROPIC FLUID SOLUTIONS WHICH MATCH TO KERR'S SOLUTION

2013 ◽  
Vol 22 (07) ◽  
pp. 1350051 ◽  
Author(s):  
E. KYRIAKOPOULOS
Keyword(s):  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Thin Shells ◽  
Closed Surfaces ◽  
Oblate Spheroids ◽  
The Family ◽  
Proper Values ◽  
Tensor Formula

We present a family of exact rotating anisotropic fluid solutions, which satisfy all energy conditions for certain values of their parameters. The components of the Ricci tensor Rμν the eigenvalues of the tensor [Formula: see text] and the energy–momentum tensor Tμν of the solutions are given explicitly. All members of the family have the ring singularity of Kerr's solution and most of them have one or two more singularities. The solutions can be matched to the solution of Kerr on three closed surfaces, which for proper values of the parameters of the solutions approximate oblate spheroids. All matching surfaces are thin shells. For some values of a constant the surface density in one of them is positive everywhere and in this surface and in its interior all energy conditions are satisfied.

scholarly journals A periodic varying deceleration parameter in f(R, T) gravity

2018 ◽  
Vol 33 (33) ◽  
pp. 1850193 ◽  
Author(s):  
P. K. Sahoo ◽  
S. K. Tripathy ◽  
Parbati Sahoo
Keyword(s):  
Deceleration Parameter ◽  
Momentum Conservation ◽  
Momentum Tensor ◽  
Oscillatory Behavior ◽  
Matter Content ◽  
Accelerated Expansion ◽  
Energy Conditions ◽  
Field Equations ◽  
Eos Parameter ◽  
Wide Range

The phenomenon of accelerated expansion of the present universe and a cosmic transit aspect is explored in the framework of a modified gravity theory known as f(R, T) gravity (where R is the Ricci scalar and T is the trace of the energy–momentum tensor of the matter content). The cosmic transit phenomenon signifies a signature flipping behavior of the deceleration parameter. We employ a periodic varying deceleration parameter and obtained the exact solution of field equations. The dynamical features of the model including the oscillatory behavior of the EOS parameter are studied. We have also explored the obvious violation of energy–momentum conservation in f(R, T) gravity. The periodic behavior of energy conditions for the model are also discussed with a wide range of the free parameters.

Non-adiabatic gravitational collapse in f(R,T) gravity with Karmarkar condition for anisotropic fluid

2020 ◽  
Vol 35 (13) ◽  
pp. 2050103 ◽  
Author(s):  
Riaz Ahmed ◽  
G. Abbas
Keyword(s):  
Gravitational Collapse ◽  
Coupling Parameter ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Interior Solution ◽  
Spatial Presence ◽  
Field Equations ◽  
Gravitational Field Equations ◽  
Radiating Star

In this paper, we have used the Karmarkar condition to the spherically symmetric non-static radiating star experiencing dissipative gravitational collapse with a heat flux in the framework of [Formula: see text] gravity, (where [Formula: see text] is Ricci scalar which replaces Lagrangian density and [Formula: see text] is the trace of energy–momentum tensor). To obtain the ultimate results of the gravitational field equations in [Formula: see text] scenario, we take a linear form of the function as [Formula: see text]. In this connection, the Karmarkar condition along with boundary condition generates a model of radiating star and enables us to completely indicate the spatial presence of gravitational potentials. Vadiya’s exterior solution across a time-like hypersurface is smoothly matched to the interior solution which allows to study the physical conduct of our model under consideration. Furthermore, we have analyzed the energy conditions of radiating star in [Formula: see text] gravity and analyzed the physical behavior of thermodynamics parameters which provide a detailed discussion of the model. For coupling parameter [Formula: see text], we successfully obtain the standard results of General Relativity.

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