Stellar systems and structure scalars

2019 ◽  
Vol 97 (5) ◽  
pp. 465-471 ◽  
Author(s):  
S. Ahmad ◽  
A. Rehman Jami ◽  
I. Ahmad ◽  
H. Sadia
Keyword(s):  
Riemann Tensor ◽  
Matter Content ◽  
Anisotropic Pressure ◽  
Energy Tensor ◽  
Spherically Symmetric ◽  
Structure Scalars ◽  
Tidal Forces ◽  
Stress Energy ◽  
Symmetric Geometry

The work is devoted to analyzing the effects of dark source polynomial curvature corrections in the mathematical modeling of radiating stars. In this scenario, we have used a particular f(R, T) model and consider the spherically symmetric geometry of relativistic interior. We assumed that our geometry is coupled with anisotropic shearing matter distribution undergoing radiating epoch with free streaming and diffusion approximation. We have calculated spherically symmetric total matter content with the help of Misner–Sharp formalism. A particular relation among anisotropic pressure, shearing viscosity, radiating parameters, energy density, and tidal forces is obtained. We then expressed this equation with the help of f(R, T) structure scalar, the scalar obtained by orthogonal decomposition of the Riemann tensor. The role of the logarithmic Ricci and trace of stress–energy tensor terms are also observed through Weyl scalar, shear, expansion scalar differential equations.

Role of modified scalar variables in the modeling of spherical fluids

2018 ◽  
Vol 15 (08) ◽  
pp. 1850140 ◽  
Author(s):  
A. Akram ◽  
A. Rehman Jami ◽  
S. Ahmad ◽  
M. Sufyan ◽  
R. Munir
Keyword(s):  
Degrees Of Freedom ◽  
Dust Cloud ◽  
Mass Function ◽  
Riemann Tensor ◽  
Ricci Scalar ◽  
Structure Scalars ◽  
Specific Distribution ◽  
Scalar Matter ◽  
Symmetric Geometry

The aim of this work is to analyze the role of shear evolution equation in the modeling of relativistic spheres in [Formula: see text] gravity. We assume that non-static diagonally symmetric geometry is coupled with dissipative anisotropic viscous fluid distributions in the presence of [Formula: see text] dark source terms. A specific distribution of [Formula: see text] cosmic model has been assumed and the spherical mass function through generic formula introduced by Misner-Sharp has been formulated. Some very important relations regarding Weyl scalar, matter variables and mass functions are being computed. After decomposing orthogonally the Riemann tensor, some scalar variables in the presence of [Formula: see text] extra degrees of freedom are calculated. The effects of the polynomial modified structure scalars in the modeling of through Weyl, shear, expansion scalar differential equations are investigated. The energy density irregularity factor has been calculated for both anisotropic radiating viscous with varying Ricci scalar and for dust cloud with present Ricci scalar corrections.

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 Complexity of dynamical sphere in self-interacting Brans–Dicke gravity

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
M. Sharif ◽  
Amal Majid
Keyword(s):  
Scalar Field ◽  
Riemann Tensor ◽  
Dissipative Systems ◽  
Anisotropic Pressure ◽  
Massive Scalar ◽  
Initial State ◽  
Spherical System ◽  
Massive Scalar Field ◽  
Structure Scalars ◽  
Definition Of

AbstractThis paper aims to derive a definition of complexity for a dynamic spherical system in the background of self-interacting Brans–Dicke gravity. We measure complexity of the structure in terms of inhomogeneous energy density, anisotropic pressure and massive scalar field. For this purpose, we formulate structure scalars by orthogonally splitting the Riemann tensor. We show that self-gravitating models collapsing homologously follow the simplest mode of evolution. Furthermore, we demonstrate the effect of scalar field on the complexity and evolution of non-dissipative as well as dissipative systems. The criteria under which the system deviates from the initial state of zero complexity is also discussed. It is concluded that complexity of the sphere increases in self-interacting Brans–Dicke gravity because the homologous model is not shear-free.

scholarly journals Spherically Symmetric Fluid Cosmological Model with Anisotropic Stress Tensor in General Relativity

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
D. D. Pawar ◽  
V. R. Patil ◽  
S. N. Bayaskar
Keyword(s):  
General Relativity ◽  
Cosmological Model ◽  
Generating Functions ◽  
Energy Tensor ◽  
Spherically Symmetric ◽  
Stress Energy Tensor ◽  
Anisotropic Stress ◽  
Stress Energy ◽  
Anisotropic Stress Tensor ◽  
Symmetric Spacetime

This paper deals with the cosmological models for the static spherically symmetric spacetime for perfect fluid with anisotropic stress energy tensor in general relativity by introducing the generating functions g(r) and w(r) and also discussing their physical and geometric properties.

scholarly journals EXACT SOLUTIONS OF BRANS–DICKE WORMHOLES IN THE PRESENCE OF MATTER

2011 ◽  
Vol 26 (40) ◽  
pp. 3067-3076 ◽  
Author(s):  
NADIEZHDA MONTELONGO GARCIA ◽  
FRANCISCO S. N. LOBO
Keyword(s):  
Scalar Field ◽  
Vacuum Solution ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Exotic Matter ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Normal Matter ◽  
Stress Energy

A fundamental ingredient in wormhole physics is the presence of exotic matter, which involves the violation of the null energy condition. Although a plethora of wormhole solutions have been explored in the literature, it is useful to find geometries that minimize the usage of exotic matter. In this work, we find exact wormhole solutions in Brans–Dicke theory where the normal matter threading the wormhole satisfies the null energy condition throughout the geometry. Thus, the latter implies that it is the effective stress–energy tensor containing the scalar field, that plays the role of exotic matter, that is responsible for sustaining the wormhole geometry. More specifically, we consider a zero redshift function and a particular choice for the scalar field and determine the remaining quantities, namely, the stress–energy tensor components and the shape function. The solution found is not asymptotically flat, so that this interior wormhole spacetime needs to be matched to an exterior vacuum solution.

Higher-dimensional gravitational collapse of perfect fluid spherically symmetric spacetime in f(R, T) gravity

2018 ◽  
Vol 33 (12) ◽  
pp. 1850065 ◽  
Author(s):  
Suhail Khan ◽  
Muhammad Shoaib Khan ◽  
Amjad Ali
Keyword(s):  
Perfect Fluid ◽  
Outer Region ◽  
Energy Tensor ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Higher Dimensional ◽  
Stress Energy ◽  
Inner Region ◽  
Symmetric Spacetime ◽  
Spherically Symmetric Spacetime

In this paper, our aim is to study (n + 2)-dimensional collapse of perfect fluid spherically symmetric spacetime in the context of f(R, T) gravity. The matching conditions are acquired by considering a spherically symmetric non-static (n + 2)-dimensional metric in the inner region and Schwarzschild (n + 2)-dimensional metric in the outer region of the star. To solve the field equations for above settings in f(R, T) gravity, we choose the stress–energy tensor trace and the Ricci scalar as constants. It is observed that two physical horizons, namely, cosmological and black hole horizons appear as a consequence of this collapse. A singularity is also formed after the birth of both the horizons. It is also observed that the term f(R0, T0) slows down the collapsing process.

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