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 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.

Self-gravitating anisotropic star using gravitational decoupling

2021 ◽  
Author(s):  
Baiju Dayanandan ◽  
T. T. Smitha ◽  
Sunil Maurya
Keyword(s):  
Compact Star ◽  
Radial Component ◽  
Energy Conditions ◽  
Regularity Conditions ◽  
Star Model ◽  
Anisotropic Solution ◽  
Seed System ◽  
The Stability ◽  
Metric Function ◽  
Anisotropic Star

Abstract This paper addresses a new gravitationally decoupled anisotropic solution for the compact star model via the minimal geometric deformation (MGD) approach. We consider a non-singular well-behaved gravitational potential corresponding to the radial component of the seed spacetime and embedding class I condition that determines the temporal metric function to solve the seed system completely. However, two different well-known mimic approaches such as pr = Θ1 1 and ρ = Θ0 0 have been employed to determine the deformation function which gives the solution of the second system corresponding to the extra source. In order to test the physical viability of the solution, we have checked several conditions such as regularity conditions, energy conditions, causality conditions, hydrostatic equilibrium, etc. Moreover, the stability of the solutions has been also discussed by the adiabatic index and its critical value. We find that the solutions set seems viable as far as observational data are concerned.

Study of some compact objects in R + 2βT gravity

2019 ◽  
Vol 28 (16) ◽  
pp. 2040005
Author(s):  
Arfa Waseem ◽  
M. Sharif
Keyword(s):  
Stellar System ◽  
Graphical Analysis ◽  
Compact Objects ◽  
Stellar Structure ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Star Models ◽  
Mit Bag Model ◽  
Text Model

The aim of this work is to examine the nature as well as physical characteristics of anisotropic spherically symmetric stellar candidates in the context of [Formula: see text] gravity. We assume that the fluid components such as pressure and energy density are related through MIT bag model equation-of-state in the interior of stellar system. In order to analyze the structure formation of some specific star models, the field equations are constructed using Krori–Barua solution in which the unknown constants are evaluated by employing observed values of radii and masses of the considered stars. We check the consistency of [Formula: see text] model through the graphical analysis of energy conditions as well as stability of stellar structure. It is found that our considered stars show viable as well as stable behavior for this model.

scholarly journals Charged anisotropic compact star core-envelope model with polytropic core and linear envelope

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
S. A. Mardan ◽  
I. Noureen ◽  
A. Khalid
Keyword(s):  
Graphical Representation ◽  
Compact Star ◽  
Compact Object ◽  
Compact Objects ◽  
Compact Stars ◽  
Physical Parameters ◽  
Polytropic Equation ◽  
Envelope Model ◽  
Linear Envelope ◽  
The Stability

AbstractThis manuscript is related to the construction of relativistic core-envelope model for spherically symmetric charged anisotropic compact objects. The polytropic equation of state is considered for core, while it is linear in the case of envelope. We present that core, envelope and the Reissner Nordstr$$\ddot{o}$$ o ¨ m exterior regions of stars match smoothly. It has been verified that all physical parameters are well behaved in the core and envelope region for the compact stars SAX J1808.4-3658 and 4U1608-52. Various physical parameters inside star are discussed herein, non-singularity and continuity at the junction has been catered as well. Impact of charged compact object together with core-envelope model on the mass, radius and compactification factor is described by graphical representation in both core and envelop regions. The stability of the model is worked out with the help of Tolman–Oppenheimer–Volkoff equations and radial sound speed.

Lorentz distributed wormhole solutions in f(T) gravity with off-diagonal tetrad under conformal motions

2020 ◽  
Vol 35 (29) ◽  
pp. 2050240
Author(s):  
Asifa Ashraf ◽  
G. Mustafa ◽  
Mushtaq Ahmad ◽  
Ibrar Hussain
Keyword(s):  
Positive Integer ◽  
Conformal Symmetry ◽  
Teleparallel Gravity ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Physical Concept ◽  
Conformal Motion ◽  
Teleparallel Theory ◽  
Theory Of Gravity ◽  
The Stability

In this work, the possible existence of wormhole solutions have been investigated in the extended teleparallel [Formula: see text] theory of gravity by incorporating the Lorentzian source of non-commutative geometry through the conformal motion. The physical concept of conformal symmetry becomes more arguable when it is discussed in the background of non-commutative geometry, especially with the Lorentzian source. In this context, two specific different models of the extended teleparallel theory, that is, [Formula: see text], and [Formula: see text] (where [Formula: see text], [Formula: see text], [Formula: see text] being real constants and [Formula: see text] a positive integer) have been studied. The corresponding energy conditions are worked out and are analyzed graphically in the presence of the conformal motion with Lorentzian source. The presence of the exotic matter has been confirmed due to the violation of null energy conditions under some particular conditions, thereby proving the existence of the wormhole geometries in both of the models under investigation. Moreover, the stability of the wormhole geometries via the Tolman-Oppenheimer-Volkov equation has been discussed. It is concluded that these wormhole solutions supported by the non-exotic matter truly exist and are well stable under the extended teleparallel gravity.

Relativistic anisotropic models for compact star with equation of state p = f(ρ)

2017 ◽  
Vol 26 (02) ◽  
pp. 1750002 ◽  
Author(s):  
S. K. Maurya ◽  
Y. K. Gupta ◽  
Baiju Dayanandan ◽  
M. K. Jasim ◽  
Ahmed Al-Jamel
Keyword(s):  
Equation Of State ◽  
Compact Star ◽  
Fluid Distribution ◽  
Anisotropic Fluid ◽  
Perfect Fluid Solution ◽  
Anisotropic Models ◽  
Star Models ◽  
Astrophysical Objects ◽  
State Formula ◽  
The Stability

We present new anisotropic models for Buchdahl [H. A. Buchdahl, Phys. Rev. 116 (1959) 1027.] type perfect fluid solution. For this purpose, we started with metric potential [Formula: see text] same as Buchdahl [H. A. Buchdahl, Phys. Rev. 116 (1959) 1027.] and [Formula: see text] is monotonically increasing function as suggested by Lake [K. Lake, Phys. Rev. D 67 (2003) 104015]. After that we determine the new pressure anisotropy factor [Formula: see text] with the help of both the metric potentials [Formula: see text] and [Formula: see text] and propose new well behaved general solution for anisotropic fluid distribution. The physical quantities like energy density, radial and tangential pressures, velocity of sound and redshift etc. are positive and finite inside the compact star. In this connection, we have studied the stability of the models, which is most vital one and also we determined the equation of state [Formula: see text] for the realistic compact star models. It is noted that the mass and radius of our models can represent the structure of realistic astrophysical objects such as Her X-1 and RXJ 1856-37.

A relativistic two-fluid model of compact stars

2017 ◽  
Vol 32 (10) ◽  
pp. 1750055 ◽  
Author(s):  
Koushik Chakraborty ◽  
Farook Rahaman ◽  
Arkopriya Mallick
Keyword(s):  
Quark Matter ◽  
Fluid Model ◽  
Compact Star ◽  
Conformal Symmetry ◽  
Compact Objects ◽  
Compact Stars ◽  
Baryonic Matter ◽  
Spacetime Geometry ◽  
Two Fluid Model ◽  
The Masses

We propose a relativistic model of compact star admitting conformal symmetry. Quark matter and baryonic matter which are considered as two different fluids, constitute the star. We define interaction equations between the normal baryonic matter and the quark matter and study the physical situations for repulsive, attractive and zero interaction between the constituent matters. The measured value of the Bag constant is used to explore the spacetime geometry inside the star. From the observed values of the masses of some compact objects, we have obtained theoretical values of the radii. Theoretical values of the radii match well with the previous predictions for such compact objects.

scholarly journals Charged compact star in f(R, T) gravity in Tolman–Kuchowicz spacetime

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Pramit Rej ◽  
Piyali Bhar ◽  
Megan Govender
Keyword(s):  
Modified Gravity ◽  
Line Element ◽  
Compact Star ◽  
Stellar System ◽  
Radial Pressure ◽  
Energy Conditions ◽  
Field Equations ◽  
Compactness Factor ◽  
Physical Validity ◽  
The Stability

AbstractIn this current study, our main focus is on modeling the specific charged compact star SAX J 1808.4-3658 (M = 0.88 $$M_{\odot }$$ M ⊙ ,  R = 8.9 km) within the framework of $$f(R,\,T)$$ f ( R , T ) modified gravity theory using the metric potentials proposed by Tolman–Kuchowicz (Tolman in Phys Rev 55:364, 1939; Kuchowicz in Acta Phys Pol 33:541, 1968) and the interior spacetime is matched to the exterior Reissner–Nordström line element at the surface of the star. Tolman–Kuchowicz metric potentials provide a singularity-free solution which satisfies the stability criteria. Here we have used the simplified phenomenological MIT bag model equation of state (EoS) to solve the Einstein–Maxwell field equations where the density profile ($$\rho $$ ρ ) is related to the radial pressure ($$p_{\mathrm{r}}$$ p r ) as $$p_{\mathrm{r}}(r) = (\rho - 4B_{\mathrm{g}})/3$$ p r ( r ) = ( ρ - 4 B g ) / 3 . Furthermore, to derive the values of the unknown constants $$a,\, b,\, B,\, C$$ a , b , B , C and the bag constant $$B_{\mathrm{g}}$$ B g , we match our interior spacetime to the exterior Reissner–Nordström line element at the surface of stellar system. In addition, to check the physical validity and stability of our suggested model we evaluate some important properties, such as effective energy density, effective pressures, radial and transverse sound velocities, relativistic adiabatic index, all energy conditions, compactness factor and surface redshift. It is depicted from our current study that all our derived results lie within the physically accepted regime which shows the viability of our present model in the context of $$f(R,\,T)$$ f ( R , T ) modified gravity.

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].

Stability of realistic stellar objects in f(R,T) gravity with anisotropic matter configuration

2019 ◽  
Vol 16 (12) ◽  
pp. 1950191 ◽  
Author(s):  
M. Zubair ◽  
Maham Lodhi ◽  
G. Abbas
Keyword(s):  
Gravitational Potential ◽  
Compact Star ◽  
Anisotropy Parameter ◽  
Field Equations ◽  
Dynamical Equations ◽  
Anisotropic Matter ◽  
Star Models ◽  
Special Cases ◽  
Barotropic Equation ◽  
Spherically Symmetric Metric

In this paper, we have obtained a new class of solutions of modified field equations (FEqs) in [Formula: see text] gravity with barotropic equation of state (EoS) i.e. [Formula: see text]. For this purpose, we assume spherically symmetric metric with anisotropic matter distribution and formulated the FEqs. We apply Durgapal transformation and choose suitable gravitational potential to solve the dynamical equations numerically. By varying parametric values [Formula: see text] and [Formula: see text] (appearing in gravitational potential), we generate special cases of solutions. We plot physical quantities like energy density, anisotropy parameter, radial and tangential pressures in all particular cases. It is concluded that all the plots hold physical acceptability criteria and show consistency which admits modified [Formula: see text] gravity for compact star models.

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