Charged anisotropic static cylindrically symmetric models

2013 ◽  
Vol 91 (2) ◽  
pp. 113-119 ◽  
Author(s):  
M. Sharif ◽  
H. Ismat Fatima
Keyword(s):  
Electromagnetic Field ◽  
Equation Of State ◽  
Energy Density ◽  
Symmetric Space ◽  
Radial Pressure ◽  
Matter Distribution ◽  
Field Equations ◽  
Stellar Objects ◽  
Cylindrically Symmetric ◽  
Barotropic Equation

In this paper, we investigate exact solutions of the field equations for charged, anisotropic, static, cylindrically symmetric space–time. We use a barotropic equation of state linearly relating the radial pressure and energy density. The analysis of the matter variables indicates a physically reasonable matter distribution. In the most general case, the central densities correspond to realistic stellar objects in the presence of anisotropy and charge. Finally, we conclude that matter sources are less affected by the electromagnetic field.

A New Model for Charged Anisotropic Matter with Modified Chaplygin Equation of State

2020 ◽  
Author(s):  
Manuel Malaver ◽  
Hamed Daei Kasmaei
Keyword(s):  
Equation Of State ◽  
Energy Density ◽  
Compact Star ◽  
Radial Pressure ◽  
Extended Version ◽  
Matter Distribution ◽  
Field Equations ◽  
New Model ◽  
Anisotropic Matter ◽  
Chaplygin Equation

In this paper, we found a new model for compact star with charged anisotropic matter distribution considering an extended version of the Chaplygin equation of state. We specify a particular form of the metric potential Z(x) that allows us to solve the Einstein-Maxwell field equations. The obtained model satisfies all physical properties expected in a realistic star such that the expressions for the radial pressure, energy density, metric coefficients, measure of anisotropy and the mass are fully well defined and are regular in the interior of star. The solution obtained in this work can have multiple applications in astrophysics and cosmology.

Dynamics and stability of charged spherical star with tilted and non-tilted congruences

2014 ◽  
Vol 29 (30) ◽  
pp. 1450165 ◽  
Author(s):  
M. Sharif ◽  
M. Zaeem Ul Haq Bhatti
Keyword(s):  
Electromagnetic Field ◽  
Energy Density ◽  
Shear Viscosity ◽  
Heat Radiation ◽  
Matter Distribution ◽  
Field Equations ◽  
Density Inhomogeneity ◽  
Dynamical Equations ◽  
Energy Density Inhomogeneity ◽  
Fluid Configuration

This paper investigates the dynamics of anisotropic viscous spherical star under the effects of electromagnetic field for a radially moving observer relative to the matter distribution, i.e. a tilted observer. We formulate relationship between tilted and non-tilted quantities using the Einstein–Maxwell field equations. The dynamical equations and equations for the Weyl tensor are constructed to examine the inhomogeneities in the fluid configuration. It is found that different factors like heat radiation, shear viscosity, electric charge and in particular congruence of the tilted observer, affect the energy density inhomogeneity of the spherical star. Finally, we study stability of the system with non-tilted frame in the presence of charge.

f(T) gravity and static wormhole solutions

2014 ◽  
Vol 29 (27) ◽  
pp. 1450137 ◽  
Author(s):  
Muhammad Sharif ◽  
Shamaila Rani
Keyword(s):  
Equation Of State ◽  
Energy Density ◽  
Radial Pressure ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Shape Functions ◽  
Field Equations ◽  
Torsion Scalar ◽  
Transverse Pressure

In this paper, we study static spherically symmetric wormhole solutions in the framework of f(T) gravity, where T represents torsion scalar. We consider non-diagonal tetrad and anisotropic distribution of the fluid. We construct expressions for matter components such as energy density, radial pressure and transverse pressure from the field equations. Taking into account a particular equation of state (EoS) in terms of traceless fluid, we discuss the behavior of energy conditions for wormhole solutions with well-known f(T) and shape functions. We conclude that physically acceptable static wormhole solutions are obtained for both these functions.

scholarly journals Plausible families of compact objects with a nonlocal equation of state

2013 ◽  
Vol 91 (4) ◽  
pp. 328-336 ◽  
Author(s):  
H. Hernández ◽  
L.A. Núñez
Keyword(s):  
Equation Of State ◽  
Total Mass ◽  
Radial Pressure ◽  
Compact Objects ◽  
Einstein Equations ◽  
Matter Distribution ◽  
Nonlocal Equation ◽  
The Family ◽  
Model Independent ◽  
Physical Variables

We present the plausibility of some models emerging from an algorithm devised to generate a one-parameter family of interior solutions for the Einstein equations. We explore how their physical variables change as the family parameter varies. The models studied correspond to anisotropic spherical matter configurations having a nonlocal equation of state. This particular type of equation of state, with no causality problems, provides at a given point the radial pressure not only as a function of the density but as a functional of the enclosed matter distribution. We have found that there are several model-independent tendencies as the parameter increases: the equation of state tends to be stiffer and the total mass becomes half of its external radius. Profiting from the concept of cracking of materials in general relativity, we obtain that these models become more potentially stable as the family parameter increases.

scholarly journals TRAPPING PHOTONS BY A LINE SINGULARITY

2003 ◽  
Vol 12 (06) ◽  
pp. 1095-1112 ◽  
Author(s):  
METIN ARIK ◽  
OZGUR DELICE
Keyword(s):  
Energy Density ◽  
Thin Shell ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Cylindrically Symmetric ◽  
Static Solutions ◽  
Line Singularity ◽  
Thick Shells

We present cylindrically symmetric, static solutions of the Einstein field equations around a line singularity such that the energy momentum tensor corresponds to infinitely thin photonic shells. Positivity of the energy density of the thin shell and the line singularity is discussed. It is also shown that thick shells containing mostly radiation are possible in a numerical solution.

scholarly journals Relativistic disks with two charged perfect fluids components

2019 ◽  
Vol 6 (1) ◽  
pp. 1-8
Author(s):  
A.C. Gutiérrez-Piñeres ◽  
C.S. Lopez-Monsalvo
Keyword(s):  
Equation Of State ◽  
Charged Fluids ◽  
Field Equations ◽  
Charged Fluid ◽  
Charge Densities ◽  
Two Fluids ◽  
Perfect Fluids ◽  
Barotropic Equation ◽  
Thin Disks ◽  
Relativistic Disks

A method to describe exact solutions of the Einstein-Maxwell field equations in terms of relativistic thin disks constituted by two perfect charged fluids is presented. Describing the surface of the disk as a single charged fluid we find explicit expressions for the rest energies, the pressures and the electric charge densities of the two fluids. An explicit example is given. The particular case of the thin disks composed by two charged perfect fluids with barotropic equation of state is also presented.

Gravitationally decoupled non-static anisotropic spherical solutions

2021 ◽  
pp. 2150145
Author(s):  
M. Sharif ◽  
Shehrbano Ahmed
Keyword(s):  
Energy Conditions ◽  
Matter Distribution ◽  
Field Equations ◽  
Anisotropic Models ◽  
Geometric Deformation ◽  
Gravitational Source ◽  
Barotropic Equation ◽  
Gravitating Systems ◽  
Deformation Approach ◽  
Anisotropic Source

This paper is devoted for the formulation of new anisotropic solutions for non-static spherically symmetric self-gravitating systems through gravitational decoupling technique. Initially, we add a gravitational source in the perfect matter distribution for inducing the effects of anisotropy in the considered model. We then decouple the field equations through minimal geometric deformation approach and derive three new anisotropic solutions. Among these, two anisotropic solutions are evaluated by applying specific constraints on anisotropic source and the third solution is obtained by employing the barotropic equation of state. The physical acceptability and stability of the anisotropic models are investigated through energy conditions and causality condition, respectively. We conclude that all the derived anisotropic solutions are physically viable as well as stable.

EXACT MODELS FOR ANISOTROPIC RELATIVISTIC STARS

2002 ◽  
Vol 11 (02) ◽  
pp. 207-221 ◽  
Author(s):  
M. K. MAK ◽  
PETER N. DOBSON ◽  
T. HARKO
Keyword(s):  
Energy Density ◽  
Density Ratio ◽  
Anisotropy Parameter ◽  
Integral Form ◽  
Radial Pressure ◽  
Physical Parameters ◽  
Field Equations ◽  
Gravitational Field Equations ◽  
Anisotropic Star ◽  
Decreasing Functions

We present a class of exact solutions of the Einstein gravitational field equations describing spherically symmetric and static anisotropic stellar type configurations. The solution is represented in a closed integral form. The energy density and both radial and tangential pressure are finite and positive inside the anisotropic star. The energy density, radial pressure, pressure-density ratio and the adiabatic speed of sound are monotonically decreasing functions. Several stellar models with the anisotropy coefficient proportional to r2 are discussed, the values of the basic physical parameters of the star (radius, mass and red shift) and bound on anisotropy parameter is obtained.

scholarly journals Some New Models of Strange Stars in 5-D Einstein-Gauss-Bonnet Gravity

2021 ◽  
Author(s):  
Manuel Malaver ◽  
Hamed Daei Kasmaei
Keyword(s):  
Equation Of State ◽  
Energy Density ◽  
Nonlinear Equation ◽  
Radial Pressure ◽  
Compact Stars ◽  
Coupling Constant ◽  
Strange Stars ◽  
Bonnet Gravity ◽  
New Models ◽  
Linear And Nonlinear

In this paper, we present some new models for anisotropic compact stars within the framework of 5-dimensional Einstein-Gauss-Bonnet (EGB) gravity with a linear and nonlinear equation of state considering a metric potential proposed for Thirukkanesh and Ragel (2012) and generalized for Malaver (2014). The new obtained models satisfy all physical requirements of a physically reasonable stellar object. Variables as energy density, radial pressure and the anisotropy are dependent of the values of the Gauss-Bonnet coupling constant

scholarly journals Cosmological solutions and finite time singularities in Finslerian geometry

2018 ◽  
Vol 33 (07n08) ◽  
pp. 1850046 ◽  
Author(s):  
Nupur Paul ◽  
S. S. De ◽  
Farook Rahaman
Keyword(s):  
Equation Of State ◽  
Finite Time ◽  
Big Bang ◽  
Momentum Tensor ◽  
Energy Conditions ◽  
Late Time ◽  
Field Equations ◽  
Spacetime Manifold ◽  
Barotropic Equation ◽  
State Formula

We consider a very general scenario of our universe where its geometry is characterized by the Finslerian structure on the underlying spacetime manifold, a generalization of the Riemannian geometry. Now considering a general energy–momentum tensor for matter sector, we derive the gravitational field equations in such spacetime. Further, to depict the cosmological dynamics in such spacetime proposing an interesting equation of state identified by a sole parameter [Formula: see text] which for isotropic limit is simply the barotropic equation of state [Formula: see text] ([Formula: see text] being the barotropic index), we solve the background dynamics. The dynamics offers several possibilities depending on this sole parameter as follows: (i) only an exponential expansion, or (ii) a finite time past singularity (big bang) with late accelerating phase, or (iii) a nonsingular universe exhibiting an accelerating scenario at late time which finally predicts a big rip type singularity. We also discuss several energy conditions and the possibility of cosmic bounce. Finally, we establish the first law of thermodynamics in such spacetime.

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