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.

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.

Wormholes supported by f(𝒢) 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(𝒢) gravity. For this purpose, we consider the viable power-law form f(𝒢) = a𝒢n 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 𝒢 increases in even and odd manner, respectively.

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 Rotating thin shells in (2 + 1)-dimensional asymptotically AdS spacetimes: Mechanical properties, machian effects, and energy conditions

2015 ◽  
Vol 24 (09) ◽  
pp. 1542022 ◽  
Author(s):  
José P. S. Lemos ◽  
Francisco J. Lopes ◽  
Masato Minamitsuji
Keyword(s):  
Energy Momentum Tensor ◽  
Energy Condition ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Thin Shells ◽  
Dominant Energy Condition ◽  
Junction Conditions ◽  
Rest Energy ◽  
Inertial Frames ◽  
Ads Spacetime

In this paper, a rotating thin shell in a (2 + 1)-dimensional asymptotically AdS spacetime is studied. The spacetime exterior to the shell is the rotating BTZ spacetime and the interior is the empty spacetime with a cosmological constant. Through the Einstein equation in (2 + 1) dimensions and the corresponding junction conditions we calculate the dynamical relevant quantities, namely, the rest energy–density, the pressure, and the angular momentum flux density. We also analyze the matter in a frame where its energy–momentum tensor has a perfect fluid form. In addition, we show that Machian effects, such as the dragging of inertial frames, also occur in rotating (2 + 1)-dimensional spacetimes. The weak and the dominant energy condition for these shells are discussed.

scholarly journals A regular scale-dependent black hole solution

2018 ◽  
Vol 27 (03) ◽  
pp. 1850032 ◽  
Author(s):  
Ernesto Contreras ◽  
Ángel Rincón ◽  
Benjamin Koch ◽  
Pedro Bargueño
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Black Hole Solution ◽  
Energy Momentum Tensor ◽  
Energy Condition ◽  
Momentum Tensor ◽  
Scale Dependence ◽  
Weak Energy Condition ◽  
Effective Energy ◽  
Regular Black Hole

In this work, we present a regular black hole solution, in the context of scale-dependent General Relativity, satisfying the weak energy condition. The source of this solution is an anisotropic effective energy–momentum tensor which appears when the scale dependence of the theory is turned-on. In this sense, the solution can be considered as a semiclassical extension of the Schwarzschild one.

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.

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.

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.

Spherically symmetric gravitational collapse in Einstein Gauss–Bonnet theory

2019 ◽  
Vol 16 (12) ◽  
pp. 1950194
Author(s):  
M. Tahir ◽  
G. Abbas
Keyword(s):  
Gravitational Collapse ◽  
Energy Momentum Tensor ◽  
Apparent Horizon ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Coupling Constant ◽  
Last Stage ◽  
Physical Quantities ◽  
Reasonable Energy

This paper deals with spherically symmetric gravitational collapse of inhomogeneous perfect fluid in Einstein Gauss–Bonnet gravity. The physical quantities have been plotted in the EGB gravity. The Ricci Scalar and Kretschmann scalar have been determined to study the curvature singularity. The shell focusing curvature singularities are generated at last stage of gravitational collapse of object. The formation of singularity and apparent horizon depends on the initial data. Also, the energy conditions have been discussed for the reasonable energy momentum tensor. The presence of GB coupling constant [Formula: see text] modifies the structure of singularity and formation of apparent horizon.

scholarly journals Energy conditions in higher derivative f(R,□R,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.

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