f(G,T)Gravity with structure scalars

New Astronomy ◽  
2021 ◽  
Vol 84 ◽  
pp. 101532
Author(s):  
M. Farasat Shamir ◽  
Madiha Hanif
Keyword(s):  
Structure Scalars

Complexity factors for static axial system in self-interacting Brans–Dicke gravity

2019 ◽  
Vol 16 (11) ◽  
pp. 1950174 ◽  
Author(s):  
M. Sharif ◽  
Amal Majid
Keyword(s):  
Scalar Field ◽  
Evolution Equations ◽  
Riemann Tensor ◽  
Additional Source ◽  
Bianchi Identities ◽  
Structure Scalars ◽  
Physical Attributes ◽  
Physical Features ◽  
Axial System

This paper explores the physical attributes of a static axial source that induce complexity within the fluid in the background of self-interacting Brans–Dicke theory. Bel’s approach is used to split the Riemann tensor and construct structure scalars that involve physical features of the fluid in the presence of scalar field. Using the evolution equations derived from Bianchi identities as well as structure scalars, five complexity factors are identified which include constraints on the scalar field. Finally, the conditions of vanishing complexity are used to present solutions for an anisotropic inhomogeneous spheroid. It is concluded that scalar field is an additional source of complexity.

scholarly journals Karmarkar scalar condition

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
J. Ospino ◽  
L. A. Núñez
Keyword(s):  
Differential Equation ◽  
Energy Density ◽  
Density Profile ◽  
Riemann Tensor ◽  
Orthogonal Decomposition ◽  
Algebraic Relation ◽  
Structure Scalars ◽  
Physical Variables ◽  
Adiabatic Case ◽  
Dissipative Dynamic

AbstractIn this work we present the Karmarkar condition in terms of the structure scalars obtained from the orthogonal decomposition of the Riemann tensor. This new expression becomes an algebraic relation among the physical variables, and not a differential equation between the metric coefficients. By using the Karmarkar scalar condition we implement a method to obtain all possible embedding class I static spherical solutions, provided the energy density profile is given. We also analyse the dynamic adiabatic case and show the incompatibility of the Karmarkar condition with several commonly assumed simplifications to the study of gravitational collapse. Finally, we consider the dissipative dynamic Karmarkar collapse and find a new solution family.

scholarly journals Influence of modification of gravity on the complexity factor of static spherical structures

2020 ◽  
Vol 495 (4) ◽  
pp. 4334-4346
Author(s):  
Z Yousaf ◽  
Maxim Yu Khlopov ◽  
M Z Bhatti ◽  
T Naseer
Keyword(s):  
Gravitational Theory ◽  
Momentum Tensor ◽  
Matter Distribution ◽  
Field Equations ◽  
Riemann Curvature Tensor ◽  
Structure Scalars ◽  
Pressure Anisotropy ◽  
Spherical Structures ◽  
Energy Density Inhomogeneity ◽  
Definition Of

ABSTRACT The aim of this paper is to generalize the definition of complexity for the static self-gravitating structure in f (R, T, Q) gravitational theory, where R is the Ricci scalar, T is the trace part of energy–momentum tensor, and Q ≡ RαβT αβ. In this context, we have considered locally anisotropic spherical matter distribution and calculated field equations and conservation laws. After the orthogonal splitting of the Riemann curvature tensor, we found the corresponding complexity factor with the help of structure scalars. It is seen that the system may have zero complexity factor if the effects of energy density inhomogeneity and pressure anisotropy cancel the effects of each other. All of our results reduce to general relativity on assuming f (R, T, Q) = R condition.

scholarly journals Hyperbolically symmetric sources in Palatini f(R) gravity

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
M. Z. Bhatti ◽  
Z. Yousaf ◽  
Z. Tariq
Keyword(s):  
Field Theory ◽  
Analytical Techniques ◽  
Gravitational Theory ◽  
Quantum Field ◽  
The Past ◽  
Structure Scalars ◽  
Algebraic Expressions ◽  
Static Solutions ◽  
Gravitational Equations ◽  
Hilbert Action

AbstractA thorough examination of static hyperbolically symmetric matter configuration in the context of Palatini f(R) gravitational theory has been carried out in this manuscript. Following the work of Herrera et al. (Phys. Rev. D 103: 024037, 2021) we worked out the modified gravitational equations and matching conditions using the Palatini technique of variation in Einstein–Hilbert action. It is found from the evaluations that the energy density along with the contribution of dark source terms is inevitably negative which is quite useful in explaining several quantum field effects, because negative energies are closely linked with the quantum field theory. Such negative energies may also assist in time-travel to the past and formation of artificial wormholes. Furthermore, we evaluated the algebraic expressions for the mass of interior hyperbolical geometry and total energy budget, i.e., the Tolman mass of the considered source. Also, the structure scalars are evaluated to analyze the properties of matter configuration. Few analytical techniques are also presented by considering several cases to exhibit the exact analytical static solutions of the modified gravitational equations.

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.

Dark energy and collapsing axial system

2016 ◽  
Vol 26 (06) ◽  
pp. 1750057 ◽  
Author(s):  
M. Sharif ◽  
Rubab Manzoor
Keyword(s):  
Energy Source ◽  
Dark Energy ◽  
Heat Transport ◽  
Source Term ◽  
Poynting Vector ◽  
Axially Symmetric ◽  
Structure Scalars ◽  
Expansion Scalar ◽  
Heat Transport Equation ◽  
Axial System

This paper investigates the effects of dark source term on the dissipative axially symmetric collapse by taking self-interacting Brans–Dicke (SBD) gravity as a dark energy (DE) candidate. We discuss physically feasible energy source of the model and formulate all the dynamical variables as well as structure scalars. It is found that the dark source term is one of the source of anisotropy and dissipation in the system. Further, we obtain structure scalars in this background. In order to discuss factors describing dissipative collapse, we develop equations related to the evolution of dynamical variables, heat transport equation as well as super-Poynting vector. We conclude that the thermodynamics of the collapse, evolution of kinematical terms (like expansion scalar, shear and vorticity) and inhomogeneity are affected by dark source term. Finally, we study the existence of radiation having repulsive gravitational nature in this collapse scenario.

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