Physical behavior of anisotropic compact stars in f(R, T, RμνTμν) gravity

2016 ◽  
Vol 94 (10) ◽  
pp. 1024-1039 ◽  
Author(s):  
M. Sharif ◽  
Arfa Waseem
Keyword(s):  
Energy Density ◽  
Compact Star ◽  
Compact Stars ◽  
Energy Conditions ◽  
Effective Energy ◽  
Stability Criteria ◽  
Physical Behavior ◽  
Regular Behavior ◽  
Star Models ◽  
Anisotropic Factor

This paper investigates the behavior of anisotropic compact stars in the background of R + αRμνTμν gravity model. For this purpose, we use Krori–Barua metric solutions where constants are calculated using masses and radii of compact stars like Her X-1, SAX J 1808.4–3658, and 4U1820–30. We analyze regular behavior of effective energy density, and radial and transverse pressures in the interior of compact stars. We also discuss energy conditions, effect of anisotropic factor, and stability criteria of these stars. It is concluded that the considered compact star models satisfy all the energy conditions and remain stable against the anisotropic effect in this gravity.

Charged compact objects in f(R,T) gravity

2019 ◽  
Vol 28 (02) ◽  
pp. 1950033 ◽  
Author(s):  
M. Sharif ◽  
Arfa Waseem
Keyword(s):  
Energy Density ◽  
Observational Data ◽  
Compact Star ◽  
Compact Objects ◽  
Energy Conditions ◽  
Star Models ◽  
Anisotropic Factor ◽  
Stellar Models ◽  
Stable Structures

This paper analyzes the effects of charge on the nature of relativistic compact star candidates with anisotropic distribution in the framework of [Formula: see text] gravity. For this purpose, we consider Krori–Barua solutions and obtain the values of unknown constants as well as charge using observational data of Her X-1, 4U1820-30 and SAX J 1808.4-3658 star models. For three viable [Formula: see text] models, we investigate the behavior of energy density, transverse as well as radial pressures in the interior geometry of these stars. The validity of energy conditions, effect of anisotropic factor and stability of these stellar models are also examined. We conclude that the effect of charge leads to more stable structures of relativistic compact objects.

BOUNDS ON f(G) GRAVITY FROM ENERGY CONDITIONS

2010 ◽  
Vol 25 (27) ◽  
pp. 2325-2332 ◽  
Author(s):  
PUXUN WU ◽  
HONGWEI YU
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Energy Density ◽  
Modified Gravity ◽  
Energy Conditions ◽  
Model Parameters ◽  
Effective Energy ◽  
Raychaudhuri Equation ◽  
Accelerating Expansion

The f(G) gravity is a theory to modify the general relativity and it can explain the present cosmic accelerating expansion without the need of dark energy. In this paper the f(G) gravity is tested with the energy conditions. Using the Raychaudhuri equation along with the requirement that the gravity is attractive in the FRW background, we obtain the bounds on f(G) from the SEC and NEC. These bounds can also be found directly from the SEC and NEC within the general relativity context by the transformations: ρ → ρm + ρE and p → pm + pE, where ρE and pE are the effective energy density and pressure in the modified gravity. With these transformations, the constraints on f(G) from the WEC and DEC are obtained. Finally, we examine two concrete examples with WEC and obtain the allowed region of model parameters.

scholarly journals A new class of relativistic model of compact stars of embedding class I

2017 ◽  
Vol 26 (09) ◽  
pp. 1750090 ◽  
Author(s):  
Piyali Bhar ◽  
Ksh. Newton Singh ◽  
Tuhina Manna
Keyword(s):  
Compact Star ◽  
Mass Function ◽  
Static Stability ◽  
Compact Stars ◽  
Stable Region ◽  
Energy Conditions ◽  
Arbitrary Form ◽  
Star Model ◽  
Field Equations ◽  
Anisotropic Matter

In the present paper, we have constructed a new relativistic anisotropic compact star model having a spherically symmetric metric of embedding class one. Here we have assumed an arbitrary form of metric function [Formula: see text] and solved the Einstein’s relativistic field equations with the help of Karmarkar condition for an anisotropic matter distribution. The physical properties of our model such as pressure, density, mass function, surface red-shift, gravitational redshift are investigated and the stability of the stellar configuration is discussed in details. Our model is free from central singularities and satisfies all energy conditions. The model we present here satisfy the static stability criterion, i.e. [Formula: see text] for [Formula: see text][Formula: see text]g/cm3(stable region) and for [Formula: see text][Formula: see text]g/cm3, the region is unstable i.e. [Formula: see text].

scholarly journals Analysis of charged compact stars in modified gravity

2018 ◽  
Vol 27 (08) ◽  
pp. 1850082 ◽  
Author(s):  
M. Farasat Shamir ◽  
Saeeda Zia
Keyword(s):  
Modified Gravity ◽  
Compact Star ◽  
Compact Object ◽  
Relative Difference ◽  
Comprehensive Analysis ◽  
Compact Stars ◽  
Energy Conditions ◽  
Anisotropic Pressure ◽  
Field Equations ◽  
Stability Energy

Current study highlights the physical characteristics of charged anisotropic compact stars by exploring some exact solutions of modified field equations in [Formula: see text] gravity. A comprehensive analysis is performed from the obtained solutions regarding stability, energy conditions, regularity, sound velocity and compactness. These solutions can be referred to model the compact celestial entities. In particular, a compact star named, [Formula: see text] has been modeled which indicates that current solution fits and is in conformity to the observational data as well. A useful and interesting fact from this model arises that relative difference between two forces of anisotropic pressure and electromagnetic force may occur inside the aforementioned compact star. This is another mechanism which is essential for stability of the compact object and prevent stellar object to annihilate.

scholarly journals Generalized compact star models with conformal symmetry

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
J. W. Jape ◽  
S. D. Maharaj ◽  
J. M. Sunzu ◽  
J. M. Mkenyeleye
Keyword(s):  
Compact Star ◽  
Conformal Symmetry ◽  
Compact Objects ◽  
Energy Conditions ◽  
Geometric Framework ◽  
Exact Model ◽  
Star Models ◽  
Special Cases ◽  
Physical Forces ◽  
The Stability

AbstractWe generate a new generalized regular charged anisotropic exact model that admits conformal symmetry in static spherically symmetric spacetime. Our model was examined for physical acceptability as realistic stellar models. The regularity is not violated, the energy conditions are satisfied, the physical forces balanced at equilibrium, the stability is satisfied via adiabatic index, and the surface red shift and mass–radius ratio are within the required bounds. Our conformal charged anisotropic exact solution contains models generated by Finch–Skea, Vaidya–Tikekar and Schwarzschild. Also, some recent charged or neutral and anisotropic or isotropic conformally symmetric models are found as special cases of our exact model. Our approach using a conformal symmetry provides a generalized geometric framework for studying compact objects.

Charged stellar structure in Tolman–Kuchowicz spacetime

2020 ◽  
Vol 17 (09) ◽  
pp. 2050140
Author(s):  
M. Farasat Shamir ◽  
I. Fayyaz
Keyword(s):  
Compact Star ◽  
Physical Stability ◽  
Stellar Model ◽  
Stellar Structure ◽  
Energy Conditions ◽  
Physical Parameters ◽  
Field Equations ◽  
Charged Fluid ◽  
Charged Fluid Sphere ◽  
Anisotropic Factor

In this paper, we have presented the Einstein–Maxwell equations which are described by the spherically symmetric spacetime in the presence of charge by exploiting the Tolman–Kuchowicz spacetime. The corresponding field equations are constructed and the form of charge distribution is chosen to be [Formula: see text], where [Formula: see text] is a constant quantity. We also find the values of unknown constants from junction conditions and discuss the behavior of effective energy density, effective radial and tangential pressure and anisotropic factor with two viable [Formula: see text] models. We examine the physical stability of charged stellar structure through energy conditions, causality and stability condition. We use modified form of TOV equation for anisotropic charged fluid sphere to analyze the equilibrium condition. In this work, we model the compact star candidate SAXJ 1808.4 – 3658 and study the compactness level and anisotropic behavior corresponding to the variation of physical parameters which are involved in [Formula: see text] models. Further, we evaluate some important properties such as mass-radius ratio compactness factor and surface redshift. It is depicted from this study that the obtained solutions provide strong evidences for more realistic and viable stellar model.

scholarly journals Study of anisotropic compact stars with quintessence field and modified chaplygin gas in f(T) gravity

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Pameli Saha ◽  
Ujjal Debnath
Keyword(s):  
Compact Star ◽  
Equations Of Motion ◽  
Matching Condition ◽  
Chaplygin Gas ◽  
Compact Stars ◽  
Energy Conditions ◽  
Modified Chaplygin Gas ◽  
Quintessence Field ◽  
Physical Quantities ◽  
Surface Redshift

Abstract In this work, we get an idea of the existence of compact stars in the background of f(T) modified gravity where T is a scalar torsion. We acquire the equations of motion using anisotropic property within the spherically compact star with electromagnetic field, quintessence field and modified Chaplygin gas in the framework of modified f(T) gravity. Then by matching condition, we derive the unknown constants of our model to obtain many physical quantities to give a sketch of its nature and also study anisotropic behavior, energy conditions and stability. Finally, we estimate the numerical values of mass, surface redshift etc from our model to compare with the observational data for different types of compact stars.

scholarly journals Relativistic compact stars in Tolman spacetime via an anisotropic approach

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Piyali Bhar ◽  
Pramit Rej ◽  
P. Mafa Takisa ◽  
M. Zubair
Keyword(s):  
Graphical Representation ◽  
Dimensional Space ◽  
Compact Star ◽  
Compact Stars ◽  
Stellar Structure ◽  
Energy Conditions ◽  
Anisotropic Pressure ◽  
Model Parameters ◽  
Theory Of Relativity ◽  
Field Equations

AbstractIn this present work, we have obtained a singularity-free spherically symmetric stellar model with anisotropic pressure in the background of Einstein’s general theory of relativity. The Einstein’s field equations have been solved by exploiting Tolman ansatz [Richard C Tolman, Phys. Rev. 55:364, 1939] in $$(3+1)$$ ( 3 + 1 ) -dimensional space-time. Using observed values of mass and radius of the compact star PSR J1903+327, we have calculated the numerical values of all the constants from the boundary conditions. All the physical characteristics of the proposed model have been discussed both analytically and graphically. The new exact solution satisfies all the physical criteria for a realistic compact star. The matter variables are regular and well behaved throughout the stellar structure. Constraints on model parameters have been obtained. All the energy conditions are verified with the help of graphical representation. The stability condition of the present model has been described through different testings.

Role of f(G,T) gravity on the evolution of relativistic stars

2018 ◽  
Vol 27 (04) ◽  
pp. 1850044 ◽  
Author(s):  
Muhammad Zaeem-ul-Haq Bhatti ◽  
M. Sharif ◽  
Z. Yousaf ◽  
M. Ilyas
Keyword(s):  
Systematic Investigation ◽  
Compact Stars ◽  
Energy Conditions ◽  
Physical Parameters ◽  
Energy Tensor ◽  
Star Model ◽  
Relativistic Stars ◽  
Star Models ◽  
Stress Energy

The aim of this paper is to explore some physically viable aspects for the possible emergence of compact stars in [Formula: see text] theory of gravity with some particular models, where [Formula: see text] and [Formula: see text] are Gauss–Bonnet invariant and trace of stress–energy tensor, respectively. We present basic formalism of this modified theory in the presence of anisotropic source. We explore some realistic aspects using the energy conditions with physical parameters. Three distinct known star models namely, [Formula: see text] [Formula: see text] and [Formula: see text], are used for this systematic investigation. The physical behavior of anisotropic stresses, energy density, energy conditions, measure of anisotropy and stability of compact stars are discussed through plots. We conclude that compactness at the core of a star model increases and energy conditions hold.

Modeling of immense gravity objects via generalized solution of Einstein’s field equations

2019 ◽  
Vol 28 (10) ◽  
pp. 1950134
Author(s):  
Kiran Pant ◽  
Pratibha Fuloria
Keyword(s):  
Mass Formula ◽  
Compact Star ◽  
Generalized Solution ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Field Equations ◽  
Star Models ◽  
Spacetime Manifold ◽  
Class 1 ◽  
Physical Features

In this paper, we generate a new generalized solution for modeling of compact anisotropic astrophysical configurations by using Karmarkar condition of embedded class 1 spacetime manifold. We demonstrate that the new solution satisfies all required physical conditions. We investigate several physical properties of compact star models, i.e. Vela X-1 (Mass [Formula: see text][Formula: see text], radius = [Formula: see text][Formula: see text]km), PSRJ [Formula: see text] (Mass [Formula: see text][Formula: see text], radius = [Formula: see text][Formula: see text]km) and PSRJ [Formula: see text] (Mass [Formula: see text][Formula: see text], radius = [Formula: see text][Formula: see text]km) in conformity with the observational data. The proposed solution is free from singularities, satisfies causality condition and displays well-behaved nature inside the anisotropic configurations. All energy conditions and hydrostatic equilibrium condition are well defined inside the anisotropic fluid spheres. The adiabatic index throughout the stellar interior is greater than [Formula: see text] and the compactification factor lies within the Buchdahl limit [Formula: see text]. We study the physical features of the solution in detail, analytically as well as graphically for compact star Vela X-1 with [Formula: see text] ranging from [Formula: see text] to [Formula: see text].

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