A study on charged compact stars

2019 ◽  
Vol 28 (03) ◽  
pp. 1950053 ◽  
Author(s):  
S. K. Maurya ◽  
Saibal Ray ◽  
Abdul Aziz ◽  
M. Khlopov ◽  
P. Chardonnet
Keyword(s):  
Maxwell Equations ◽  
Stellar System ◽  
Compact Stars ◽  
Physical Analysis ◽  
Field Equations ◽  
Electromagnetic Mass ◽  
Regular Solutions ◽  
Mass Model ◽  
Class 1 ◽  
Physical Features

In this paper, the Einstein–Maxwell spacetime is considered for compact stellar system. To find out solutions of the field equations, we adopt a finite and positive well-behaved metric potential. Under this particular choice, we therefore develop the expressions of the physical features, such as mass, charge, density and pressure, for stellar system in embedding class 1 spacetime. It is observed that all these features are physically viable. In the model, some known compact stars, viz. [Formula: see text] 1820–30, [Formula: see text] 1608–52 and [Formula: see text] 1745–248 [Formula: see text] are studied successfully through physical analysis. It is also interesting to note that the obtained set of regular solutions to the Einstein–Maxwell equations represents an electromagnetic mass model for isotropic fluid without invoking any negative pressure.

scholarly journals ELECTROMAGNETIC MASS IN (n + 2)-DIMENSIONAL SPACE–TIMES

2006 ◽  
Vol 15 (06) ◽  
pp. 917-923 ◽  
Author(s):  
SAIBAL RAY
Keyword(s):  
Dimensional Space ◽  
Mass Density ◽  
Space Time ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Electromagnetic Mass ◽  
Mass Model ◽  
Solution Sets ◽  
Higher Dimensional ◽  
Physical Features

Einstein–Maxwell field equations corresponding to a higher-dimensional description of static spherically symmetric space–time are solved under two specific sets of conditions: (i) ρ ≠ 0, ν′ = 0 and (ii) ρ = 0, ν′ ≠ 0, where ρ and ν represent the mass density and metric potential. The solution sets thus obtained satisfy the criteria of being an electromagnetic mass model such that the gravitational mass vanishes for the vanishing charge density σ and also the space–time becomes flat. Physical features related to other parameters are also discussed.

scholarly journals Compact stars in f(ℛ,𝒢,𝒯 ) gravity

2021 ◽  
Vol 36 (24) ◽  
pp. 2150165
Author(s):  
M. Ilyas
Keyword(s):  
Test Particle ◽  
Gravitational Theory ◽  
Momentum Tensor ◽  
Conservation Equation ◽  
Compact Objects ◽  
Compact Stars ◽  
Energy Conditions ◽  
Field Equations ◽  
Physical Features ◽  
The Impact

This work is to introduce a new kind of modified gravitational theory, named as [Formula: see text] (also [Formula: see text]) gravity, where [Formula: see text] is the Ricci scalar, [Formula: see text] is Gauss–Bonnet invariant and [Formula: see text] is the trace of the energy–momentum tensor. With the help of different models in this gravity, we investigate some physical features of different relativistic compact stars. For this purpose, we develop the effectively modified field equations, conservation equation, and the equation of motion for test particle. Then, we check the impact of additional force (massive test particle followed by a nongeodesic line of geometry) on compact objects. Furthermore, we took three notable stars named as [Formula: see text], [Formula: see text] and [Formula: see text]. The physical behavior of the energy density, anisotropic pressures, different energy conditions, stability, anisotropy, and the equilibrium scenario of these strange compact stars are analyzed through various plots. Finally, we conclude that the energy conditions hold, and the core of these stars is so dense.

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].

scholarly journals Anisotropic strange star with Tolman V potential

2018 ◽  
Vol 27 (08) ◽  
pp. 1850089 ◽  
Author(s):  
Dibyendu Shee ◽  
Debabrata Deb ◽  
Shounak Ghosh ◽  
Saibal Ray ◽  
B. K. Guha
Keyword(s):  
Stellar System ◽  
Energy Condition ◽  
Anisotropy Parameter ◽  
Stellar Model ◽  
Compact Stars ◽  
Anisotropic Fluid ◽  
Physical Parameters ◽  
Model Matching ◽  
Field Equations ◽  
Bag Constant

In this paper, we present a strange stellar model using Tolman [Formula: see text]-type metric potential employing simplest form of the MIT bag equation of state (EOS) for the quark matter. We consider that the stellar system is spherically symmetric, compact and made of an anisotropic fluid. Choosing different values of [Formula: see text] we obtain exact solutions of the Einstein field equations and finally conclude that for a specific value of the parameter [Formula: see text], we find physically acceptable features of the stellar object. Further, we conduct different physical tests, viz., the energy condition, generalized Tolman–Oppeheimer–Volkoff (TOV) equation, Herrera’s cracking concept, etc., to confirm the physical validity of the presented model. Matching conditions provide expressions for different constants whereas maximization of the anisotropy parameter provides bag constant. By using the observed data of several compact stars, we derive exact values of some of the physical parameters and exhibit their features in tabular form. It is to note that our predicted value of the bag constant satisfies the report of CERN-SPS and RHIC.

scholarly journals Constraining values of bag constant for strange star candidates

2019 ◽  
Vol 28 (13) ◽  
pp. 1941006 ◽  
Author(s):  
Abdul Aziz ◽  
Saibal Ray ◽  
Farook Rahaman ◽  
M. Khlopov ◽  
B. K. Guha
Keyword(s):  
Compact Star ◽  
A Priori ◽  
Stellar System ◽  
Mass Function ◽  
Strange Star ◽  
Compact Stars ◽  
Stellar Structure ◽  
Star Model ◽  
Field Equations ◽  
Bag Constant

We provide a strange star model under the framework of general relativity by using a general linear equation of state (EOS). The solution set thus obtained is employed on altogether 20 compact star candidates to constraint values of MIT bag model. No specific value of the bag constant ([Formula: see text]) a priori is assumed, rather possible range of values for bag constant is determined from observational data of the said set of compact stars. To do so, the Tolman–Oppenheimer–Volkoff (TOV) equation is solved by homotopy perturbation method (HPM) and hence we get a mass function for the stellar system. The solution to the Einstein field equations represents a nonsingular, causal and stable stellar structure which can be related to strange stars. Eventually, we get an interesting result on the range of the bag constant as [Formula: see text]. We have found the maximum surface redshift [Formula: see text] and shown that the central redshift ([Formula: see text]) cannot have value larger than [Formula: see text], where [Formula: see text]. Also, we provide a possible value of bag constant for neutron star with quark core using hadronic as well as quark EOS.

Exploring physical features of anisotropic quark stars in Brans-Dicke theory with a massive scalar field via embedding approach

2021 ◽  
Author(s):  
Abdelghani Errehymy ◽  
G. Mustafa ◽  
Youssef Khedif ◽  
Mohammed Daoud
Keyword(s):  
Scalar Field ◽  
Coupling Parameter ◽  
Stellar System ◽  
Stellar Model ◽  
Compact Stars ◽  
Energy Conditions ◽  
Field Equations ◽  
Massive Scalar Field ◽  
Quark Stars ◽  
Free Fermi

Abstract The main aim of this manuscript is to explore the existence and salient features of spherically symmetric relativistic quark stars in the background of massive Brans-Dicke gravity. The exact solutions to the modified Einstein field equations are derived for specific forms of coupling and scalar field functions by using the equation of state relating to the strange quark matter that stimulates the phenomenological MIT-Bag model as a free Fermi gas of quarks. We use a well-behaved function along with Karmarkar condition for class-one embedding as well as junction conditions to determine the unknown metric tensors. The radii of the strange compact stars viz., PSR J1416-2230, PSR J1903+327, 4U 1820-30, CenX-3, EXO1785-248 are predicted via their observed mass for different values of the massive Brans-Dicke parameters. We explore the influences of mass of scalar field $m_{\phi}$ as well as coupling parameter $\omega_{BD}$ along with bag constant $\mathcal{B}$ on state determinants and perform several tests on the viability and stability of the constructed stellar model. Conclusively, we find that our stellar system is physically viable and stable as it satisfies all the energy conditions as well as necessary stability criteria under the influence of a gravitational scalar field.

scholarly journals GENERALIZED EINSTEIN–MAXWELL FIELD EQUATIONS IN THE PALATINI FORMALISM

2013 ◽  
Vol 22 (04) ◽  
pp. 1350017 ◽  
Author(s):  
GINÉS R. PÉREZ TERUEL
Keyword(s):  
Electromagnetic Field ◽  
Algebraic Equation ◽  
Ricci Tensor ◽  
Maxwell Equations ◽  
Natural Generalization ◽  
New Method ◽  
Maxwell Field ◽  
Field Equations ◽  
Palatini Formalism

We derive a new set of field equations within the framework of the Palatini formalism. These equations are a natural generalization of the Einstein–Maxwell equations which arise by adding a function [Formula: see text], with [Formula: see text] to the Palatini Lagrangian f(R, Q). The result we obtain can be viewed as the coupling of gravity with a nonlinear extension of the electromagnetic field. In addition, a new method is introduced to solve the algebraic equation associated to the Ricci tensor.

Anisotropic compact stars model with generalized Bardeen–Hayward mass function

2021 ◽  
Vol 36 (26) ◽  
pp. 2150190
Author(s):  
Nayan Sarkar ◽  
Susmita Sarkar ◽  
Farook Rahaman ◽  
Ksh. Newton Singh
Keyword(s):  
Surface Density ◽  
Mass Function ◽  
Static Stability ◽  
Compact Stars ◽  
Energy Conditions ◽  
Causality Condition ◽  
Field Equations ◽  
Regular Black Hole ◽  
Bag Constant ◽  
Tov Equation

A new compact stars nonsingular model is presented with the generalized Bardeen–Hayward mass function. Generalized Bardeen–Hayward described the regular black hole, however, due to its regularity or nonsingular nature we were inspired to construct an anisotropic compact stars model. Along with the ansatz mass function, we coupled it with a linear equation of state (EoS) to find the solutions of field equations. Indeed, the new solutions are physically viable in all physical ground. The energy conditions and Tolman–Oppenheimer–Volkoff (TOV)-equation are well satisfied signifying that the mass distribution is physically possible and at equilibrium. Also, the static stability criterion, the causality condition and Abreu’s stability condition hold good and therefore configurations are physically static stable. The same condition is further supported by the condition that the adiabatic index, which is greater than the Newtonian limit, i.e. [Formula: see text]. It is also noticed that the bag constant [Formula: see text] is proportional to the surface density in our model.

Wormhole solutions in embedding class 1 space–time

2021 ◽  
Vol 36 (02) ◽  
pp. 2150015
Author(s):  
Nayan Sarkar ◽  
Susmita Sarkar ◽  
Farook Rahaman ◽  
Safiqul Islam
Keyword(s):  
Dimensional Space ◽  
Vacuum Solution ◽  
Energy Condition ◽  
Radial Distance ◽  
Space Time ◽  
Exotic Matter ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Asymptotically Flat ◽  
Class 1

The present work looks for new spherically symmetric wormhole solutions of the Einstein field equations based on the well-known embedding class 1, i.e. Karmarkar condition. The embedding theorems have an interesting property that connects an [Formula: see text]-dimensional space–time to the higher-dimensional Euclidean flat space–time. The Einstein field equations yield the wormhole solution by violating the null energy condition (NEC). Here, wormholes solutions are obtained corresponding to three different redshift functions: rational, logarithm, and inverse trigonometric functions, in embedding class 1 space–time. The obtained shape function in each case satisfies the flare-out condition after the throat radius, i.e. good enough to represents wormhole structure. In cases of WH1 and WH2, the solutions violate the NEC as well as strong energy condition (SEC), i.e. here the exotic matter content exists within the wormholes and strongly sustains wormhole structures. In the case of WH3, the solution violates NEC but satisfies SEC, so for violating the NEC wormhole preserve due to the presence of exotic matter. Moreover, WH1 and WH2 are asymptotically flat while WH3 is not asymptotically flat. So, indeed, WH3 cutoff after some radial distance [Formula: see text], the Schwarzschild radius, and match to the external vacuum solution.

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