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 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 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 A Cosmological Scenario from the Starobinsky Model within the f(R,T) Formalism

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
P. H. R. S. Moraes ◽  
P. K. Sahoo ◽  
G. Ribeiro ◽  
R. A. C. Correa
Keyword(s):  
Functional Form ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Starobinsky Model ◽  
Cosmological Scenario ◽  
Expansion Of The Universe ◽  
Theory Of Gravitation ◽  
Free Parameters ◽  
The Universe

In this paper we derive a novel cosmological model from the f(R,T) theory of gravitation, for which R is the Ricci scalar and T is the trace of the energy-momentum tensor. We consider the functional form f(R,T)=f(R)+f(T), with f(R) being the Starobinsky Model, named R+αR2, and f(T)=2γT, with α and γ being constants. We show that a hybrid expansion law form for the scale factor is a solution for the derived Friedmann-like equations. In this way, the model is able to predict both the decelerated and the accelerated regimes of expansion of the universe, with the transition redshift between these stages being in accordance with recent observations. We also apply the energy conditions to our material content solutions. Such an application makes us able to obtain the range of acceptability for the free parameters of the model, named α and γ.

Begründung des Energie-Impuls-Tensors der allgemeinen Relativitätstheorie auf Grund eines kinetischen Modells der Materie

1967 ◽  
Vol 22 (5) ◽  
pp. 808-815
Author(s):  
Jürgen Audretsch
Keyword(s):  
Energy Momentum Tensor ◽  
State Equation ◽  
Momentum Tensor ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Particle Properties ◽  
Energy And Momentum ◽  
Generally Covariant ◽  
Stream Lines ◽  
Special Time

The energy-momentum tensor Tαβ of the general theory of relativity is investigated on the basis of a kinetic model of matter (point-particles). Its freedom of divergence results from the motion of the particles. After a suitable decomposition of Tαβ into its invariant components these can be interpreted in a generally covariant manner according to their microstructure. By means of the distribution of matter special time-like world-lines are designated as stream-lines. The freedom of divergence of Tαβ can be interpreted by virtue of the model as a local balance of energy and momentum. In this balance the influence of gravitational and inertial forces become immediately evident. Pressure results as a function of the particle properties (state equation).

scholarly journals An Analysis for Conservative and Non-conservative f(R, T) Gravity Models

2021 ◽  
pp. 1-11
Author(s):  
Diyadin Can ◽  
Ertan Güdekli
Keyword(s):  
Energy Condition ◽  
Hubble Constant ◽  
Momentum Tensor ◽  
Cosmic Acceleration ◽  
Gravity Models ◽  
Energy Conditions ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Acceleration Of The Universe ◽  
The Universe

As it is known that General Theory of Relativity does not explain the current acceleration of the universe, so there are many attempts to generalize this theory in order to explain the cosmic acceleration without introducing some dark components such as the Dark Energy. Because of the crowd of models in literature, a need to check the models according to some criteria arises. In this study, we analyze two classes of models by means of energy condition restrictions and illustrate the analysis of those classes by graphical simulations. We consider the conservative and non-conservative cases of two classes of  models to perform the analysis. The results of the viability of the classes are discussed and it is found that the value of the Hubble constant has no effect on the viability of the models. Focusing on some general classes for the models, we restrict them by means of the so-called energy conditions the energy-momentum tensor on physical grounds. Besides, we find numerical values for coefficients of those classes of models.

scholarly journals A NON- STATIC COSMOLOGICAL MODEL IN THE VECTOR MODEL FOR GRAVITATIONAL FIELD

2011 ◽  
Vol 14 (1) ◽  
pp. 78-84
Author(s):  
On Van Vo
Keyword(s):  
Gravitational Field ◽  
General Theory ◽  
Cosmological Model ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Vector Model ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
S Model

In this paper, based on the vector model for gravitational field we obtained the modified Friedman equations, which were similar to the classical Friedman equations but were added a term of energy – momentum tensor of gravitational field. Non- static flat cosmological model in this model was similar to General Theory of Relativity (GTR) ‘s model but the expansive rate in the vacuum age was difference with General Theory of Relativity ’s model.

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 Bounds on higher derivative f(R,□R,T) models from energy conditions

2019 ◽  
Vol 34 (11) ◽  
pp. 1950082 ◽  
Author(s):  
M. Ilyas ◽  
Z. Yousaf ◽  
M. Z. Bhatti
Keyword(s):  
Perfect Fluid ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Ricci Scalar ◽  
Energy Conditions ◽  
Higher Derivative ◽  
Derivative Formula ◽  
Cosmological Solutions ◽  
Walker Metric ◽  
Cosmic Parameters

This paper studies the viable regions of some cosmic models in a higher derivative [Formula: see text] theory with the help of energy conditions (where [Formula: see text], [Formula: see text] and [Formula: see text] are the Ricci scalar, d’Alembert’s operator and trace of energy–momentum tensor, respectively). For this purpose, we assume a flat Friedmann–Lemaître–Robertson–Walker metric which is assumed to be filled with perfect fluid configurations. We take two distinct realistic models that might be helpful to explore stable regimes of cosmological solutions. After taking some numerical values of cosmic parameters, like crackle, snap, jerk (etc.) as well as viable constraints from energy conditions, the viable zones for the under observed [Formula: see text] models are examined.

An Action-at-a-Distance Theory of Gravitation

1971 ◽  
Vol 49 (2) ◽  
pp. 201-217 ◽  
Author(s):  
A. B. Volkov
Keyword(s):  
Momentum Conservation ◽  
Dielectric Dispersion ◽  
Interaction Theory ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Vector Interaction ◽  
Perihelion Advance ◽  
Theory Of Gravitation ◽  
Action At A Distance ◽  
Energy And Momentum

An action-at-a-distance theory is formulated as a possible alternative to the general theory of relativity. The observed gravitational frequency shift and light bending are obtained by photon energy and momentum conservation effects and gravitational–electromagnetic phenomena are interpreted in analogy with the quantum theory of dielectric dispersion. The observed perihelion advance of Mercury is obtained by a combined scalar and vector interaction theory of the Wheeler–Feynman type. The vector interaction is no longer excluded by conventional field theoretic arguments.

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.

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