scholarly journals Study of generalized cylindrical polytropes with complexity factor

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Shiraz Khan ◽  
S. A. Mardan ◽  
M. A. Rehman
Keyword(s):  
Equation Of State ◽  
Energy Density ◽  
Differential Equations ◽  
Mass Density ◽  
Modify Form ◽  
Graphical Analysis ◽  
Fluid Distribution ◽  
Anisotropic Fluid ◽  
Polytropic Equation ◽  
Frame Work

AbstractIn this paper, complexity factor is used with generalized polytropic equation of state to develop two consistent systems of three differential equations and a general frame work is established for modify form of Lane-Emden equations. For this purpose anisotropic fluid distribution is considered in cylindrical static symmetry with two cases of generalized polytropic equation of state (i) mass density $$\mu _{o}$$ μ o and (ii) energy density $$\mu $$ μ . A graphical analysis will be carried out for the numerical solution of these systems of three differential equations.

scholarly journals Framework for generalized polytropes with complexity factor

2019 ◽  
Vol 79 (12) ◽  
Author(s):  
Shiraz Khan ◽  
S. A. Mardan ◽  
M. A. Rehman
Keyword(s):  
Equation Of State ◽  
Energy Density ◽  
Differential Equations ◽  
Spherical Symmetry ◽  
Mass Density ◽  
Fluid Distribution ◽  
System Of Differential Equations ◽  
Systems Of Differential Equations ◽  
Polytropic Equation

AbstractA framework is developed for generalized polytropes with the help of complexity factor introduced by Herrera (Phy Rev D 97:044010, 2018), by using the spherical symmetry with anisotropic inner fluid distribution. For this purpose generalized polytropic equation of state will be used, having two cases (i) for mass density $$(\mu _{o})$$(μo), (ii) for energy density $$(\mu )$$(μ), each case leads to a system of differential equations. These systems of differential equations involve two equations with three unknowns and they will be made consistent by using the complexity factor. The analysis of the solutions of these systems will be carried out graphically by using different parametric values involved in the systems.

scholarly journals Impact of generalized polytropic equation of state on charged anisotropic polytropes

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
S. A. Mardan ◽  
M. Rehman ◽  
I. Noureen ◽  
R. N. Jamil
Keyword(s):  
Equation Of State ◽  
Speed Of Sound ◽  
Graphical Analysis ◽  
Maxwell Field ◽  
Anisotropic Fluid ◽  
Polytropic Index ◽  
Model Parameters ◽  
Field Equations ◽  
Polytropic Equation ◽  
Fluid Configuration

Abstract In this paper, generalized polytropic equation of state is used to get new classes of polytropic models from the solution of Einstein-Maxwell field equations for charged anisotropic fluid configuration. The models are developed for different values of polytropic index $$n=1,~\frac{1}{2},~2$$n=1,12,2. Masses and radii of eight different stars have been regained with the help of developed models. The speed of sound technique and graphical analysis of model parameters is used for the viability of developed models. The analysis of models indicates they are well behaved and physically viable.

Complexity factors for static anisotropic axially symmetric fluid distributions in f(R) gravity

2020 ◽  
Vol 17 (03) ◽  
pp. 2050043
Author(s):  
G. Abbas ◽  
H. Nazar
Keyword(s):  
Energy Density ◽  
General Theory ◽  
Graphical Analysis ◽  
Fluid Distribution ◽  
Anisotropic Fluid ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Axially Symmetric ◽  
Structure Scalars ◽  
Isotropic Pressure

In this paper, we have analyzed the complexity factor for the most general axially symmetric static anisotropic fluid distributions in context of [Formula: see text] theory of gravity. For this purpose, we have studied three distinct complexity factors that are organized in terms of three scalar variables (structure scalars) comes from the orthogonal splitting of the curvature tensor. The vanishing of all complexity factors condition for what we choose the simplest fluid distribution that in which system having energy density is homogeneous with isotropic pressure. Although, it has been found that the complexity factors condition can also vanish when inhomogeneous energy density and anisotropy of the pressure cancel each other. Next, we express a class of exact solutions and their graphical analysis as compatible to our models that satisfies the vanishing condition of complexity factors. Finally, it is worth mentioning that these results can reproduce the results of General theory of Relativity under some constraints.

OF CHARGED STARS AND CHARGED BLACK HOLES

2004 ◽  
Vol 13 (07) ◽  
pp. 1375-1379 ◽  
Author(s):  
MANUEL MALHEIRO ◽  
RODRIGO PICANÇO ◽  
SUBHARTHI RAY ◽  
JOSÉ P. S. LEMOS ◽  
VILSON T. ZANCHIN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Charged Particle ◽  
Equation Of State ◽  
Mass Density ◽  
Compact Star ◽  
Maximum Amount ◽  
Stellar Structure ◽  
Charged Black Holes ◽  
Polytropic Equation

Effect of maximum amount of charge a compact star can hold, is studied here. We analyze the different features in the renewed stellar structure and discuss the reasons why such huge charge is possible inside a compact star. We studied a particular case of a polytropic equation of state (EOS) assuming the charge density is proportional to the mass density. Although the global balance of force allows a huge charge, the electric repulsion faced by each charged particle forces it to leave the star, resulting in the secondary collapse of the system to form a charged black hole.

scholarly journals Physically Acceptable Embedded Class-I Compact Stars in Modified Gravity with Karmarkar Condition

Symmetry ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 962 ◽  
Author(s):  
Saira Waheed ◽  
Ghulam Mustafa ◽  
Muhammad Zubair ◽  
Asifa Ashraf
Keyword(s):  
Compact Star ◽  
Graphical Analysis ◽  
Specific Model ◽  
Compact Stars ◽  
Fluid Distribution ◽  
Anisotropic Fluid ◽  
Strong Impact ◽  
Metric Tensor ◽  
Physical Conditions ◽  
New Family

The present study is devoted to explore the existence of a new family of compact star solutions by adopting the Karmarkar as well as Pandey–Sharma condition in the background of f ( R , T ) modified gravitational framework. For this purpose, we consider static spherically symmetric spacetime with anisotropic fluid distribution in absence of electric charge. In respect of Karmarkar condition, we assume a specific model of g r r metric potential representing a new family of solutions which is also compatible with the Pandey–Sharma condition. This assumed model permits us to calculate the g t t component of metric tensor by making the use of Karmarkar condition. Further, we investigate the interior solutions for V e l a X − 1 model of compact star by utilizing this new family of solutions for different values of parameter λ . We have tuned the solution for V e l a X − 1 so that the solutions matches the observed mass and radius. For the same star we have extensively discussed the behavior of the solutions. It is found that these solutions fulfill all the necessary conditions under the observational radii and mass attribute data for small values of parameter λ and hence physically well-behaved and promising. Through graphical analysis, it is observed that our obtained analytical solutions are physically acceptable with a best degree of accuracy for n ∈ [ 1.8 , 7 ) − { 2 , 4 , 6 } , where parameter n is involved in the discussed model. It is also noticed the causality condition is violated for all n ≥ 7 and the tangential sound velocity v t is observed as complex valued for all 0 < n < 1.8 . Likewise, we explore these properties by considering large parameter λ values. It is seen that the presented model violates all the physical conditions for n ∈ { 2 , 4 , 6 } , while some of these for large values of λ . Consequently, it can be concluded that the parameters n and λ have a strong impact on the obtained solutions.

scholarly journals DARK ENERGY IN GLOBAL BRANE UNIVERSE

2007 ◽  
Vol 16 (10) ◽  
pp. 1633-1640 ◽  
Author(s):  
YONGLI PING ◽  
LIXIN XU ◽  
CHENGWU ZHANG ◽  
HONGYA LIU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Exact Solutions ◽  
Deceleration Parameter ◽  
Mass Density ◽  
Density Parameter ◽  
Dark Energy Density ◽  
Friedmann Equations

We discuss the exact solutions of brane universes and the results indicate that the Friedmann equations on the branes are modified with a new density term. Then, we assume the new term as the density of dark energy. Using Wetterich's parametrization equation of state (EOS) of dark energy, we obtain that the new term varies with the redshift z. Finally, the evolutions of the mass density parameter Ω2, dark energy density parameter Ωx and deceleration parameter q2 are studied.

scholarly journals Wormhole solutions in f(R) gravity theory for Chaplygin gas scenario

2021 ◽  
pp. 2150119
Author(s):  
Bikram Ghosh ◽  
Saugata Mitra
Keyword(s):  
Equation Of State ◽  
Energy Density ◽  
Chaplygin Gas ◽  
Tidal Force ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Shape Functions ◽  
Tangential Pressure ◽  
Constant Energy ◽  
State Formula

This paper deals with some wormhole solutions which are obtained by taking two different shape functions along with zero tidal force. For obtaining wormhole solutions, anisotropic fluid and a equation of state [Formula: see text] related by Chaplygin gas are considered, where [Formula: see text] is the energy density, [Formula: see text] is tangential pressure and [Formula: see text] is positive constant. Energy conditions are examined for two different models, and it is found that major energy conditions are satisfied in a region.

scholarly journals Dark Energy Stars with Quadratic Equation of State

2019 ◽  
Author(s):  
Manuel Malaver ◽  
Hamed Kasmaei
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Condition ◽  
Scalar Fields ◽  
Quadratic Equation ◽  
Accelerated Expansion ◽  
Fluid Distribution ◽  
Anisotropic Fluid ◽  
Field Equations ◽  
Quadratic Equation Of State

Recent astronomical observations with respect to measurements in distant supernovas, cosmic microwave background and weak gravitational lensing confirm that the Universe is undergoing a phase of accelerated expansion and it has been proposed that this cosmological behavior is caused by a hypothetical dark energy which has a strong negative pressure that allows explain the expanding universe. Several theoretical ideas and models related dark the energy includes the cosmological constant, quintessence, Chaplygin gas, braneworld and tachyonic scalar fields. In this paper, we have obtained new relativistic stellar configurations considering an anisotropic fluid distribution with a charge distribution which could represents a potential model of a dark energy star. In order to investigate the effect of a quadratic equation of state in this anisotropic model we specify particular forms for the gravitational potential that allow solving the Einstein-Maxwell field equations. For these new solutions we checked that the radial pressure, metric coefficients, energy density, anisotropy factor, charge density , mass function are well defined and are regular in the interior of the star. The solutions found can be used in the development of dark energy stars models satisfying all physical acceptability conditions but the causality condition and strong energy condition are violated. We expect that these models have multiple applications in astrophysics and cosmology.

scholarly journals Expansion-free cylindrically symmetric models

2012 ◽  
Vol 90 (9) ◽  
pp. 865-870 ◽  
Author(s):  
M. Sharif ◽  
Z. Yousaf
Keyword(s):  
Energy Density ◽  
Weyl Tensor ◽  
Thin Shell ◽  
Fluid Distribution ◽  
Anisotropic Fluid ◽  
Junction Condition ◽  
Free Condition ◽  
Cylindrically Symmetric ◽  
Vacuum Cavity ◽  
Boundary Surfaces

This paper investigates cylindrically symmetric distribution of an anisotropic fluid under the expansion-free condition, which requires the existence of a vacuum cavity within the fluid distribution. We have discussed two families of solutions that further provide two exact models in each family. Some of these solutions satisfy the Darmois junction condition while some show the presence of a thin shell on both boundary surfaces. We also formulate a relation between the Weyl tensor and energy density.

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