Dynamical instability of anisotropic homogeneous cylinder

2019 ◽  
Vol 35 (05) ◽  
pp. 2050009 ◽  
Author(s):  
M. Sharif ◽  
Qanitah Ama-Tul-Mughani
Keyword(s):  
Variational Principle ◽  
Characteristic Frequency ◽  
Radial Pressure ◽  
Baryon Number ◽  
Dynamical Instability ◽  
Tangential Pressure ◽  
Dynamical Equations ◽  
Anisotropic Matter ◽  
Cylindrically Symmetric ◽  
Homogeneous Cylinder

In this paper, we consider a non-static cylindrically symmetric self-gravitating system with anisotropic matter configuration and investigate its stability regions by using a homogenous model. We establish perturbed form of dynamical equations by using Eulerian and Lagrangian approaches. The conservation of baryon number is applied to obtain adiabatic index as well as perturbed pressure. A variational principle is used to find characteristic frequency which helps to compute the instability criteria. It is found that dynamical instability can be prevented till the radius of a cylinder exceeds the limit R[Formula: see text]18. We conclude that the system becomes unstable against radial oscillations as the radial pressure increases relative to tangential pressure.

Electromagnetic effects on the stability of anisotropic cylinder

2020 ◽  
Vol 35 (15) ◽  
pp. 2050124
Author(s):  
M. Sharif ◽  
Qanitah Ama-Tul-Mughani
Keyword(s):  
Radial Pressure ◽  
Baryon Number ◽  
Dynamical Instability ◽  
Perturbation Scheme ◽  
Dynamical Equations ◽  
Anisotropic Cylinder ◽  
Cylindrically Symmetric ◽  
Radial Perturbation ◽  
The Stability ◽  
Gaseous Star

This paper is devoted to analyzing the stability of charged anisotropic cylinder using the radial perturbation scheme. For this purpose, we consider the non-static cylindrically symmetric self-gravitating system and apply both Eulerian as well as Lagrangian approaches to establish a linearized perturbed form of dynamical equations. The conservation of baryon number is used to evaluate perturbed radial pressure in terms of an adiabatic index. A variational principle is developed to find a characteristic frequency which helps to examine the combined effect of charge and anisotropy on the stability of gaseous star. It is found that dynamical instability can be prevented until the radius of cylinder exceeds the limit [Formula: see text] and anisotropy increases the instability up to the limiting value of [Formula: see text]. Finally, we conclude that the system becomes more stable by increasing the definite amount of charge gradually.

Variational principle and dynamical equations of discrete nonconservative holonomic systems

2006 ◽  
Vol 15 (2) ◽  
pp. 249-252 ◽  
Author(s):  
Liu Rong-Wan ◽  
Zhang Hong-Bin ◽  
Chen Li-Qun
Keyword(s):  
Variational Principle ◽  
Dynamical Equations ◽  
Holonomic Systems

A generalized anisotropic model for super dense stars

2021 ◽  
pp. 2150070
Author(s):  
Joaquin Estevez-Delgado ◽  
Gabino Estevez-Delgado ◽  
Noel Enrique Rodríguez Maya ◽  
José Martínez Peña ◽  
Aurelio Tamez Murguía
Keyword(s):  
Radial Pressure ◽  
Compact Stars ◽  
Anisotropic Model ◽  
Speed Of Light ◽  
Matter Distribution ◽  
Sphere Model ◽  
Tangential Pressure ◽  
Relativistic Fluid ◽  
Causal Condition ◽  
Dense Stars

A static anisotropic relativistic fluid sphere model with regular geometry and finite hydrostatic functions is presented. In the interior of the sphere, the density, radial pressure and tangential pressure are positives, monotonically decreasing with increasing radius and the radial pressure vanishes at the surface of the matter distribution and is joined continuously to the exterior Schwarzschild’s solution at this surface. The speeds of the radial and tangential sound are positive and lower than the speed of light, that is, the causal condition is not violated, and also the behavior of these guarantees that the model is potentially stable. Furthermore, the range of the compactness ratio is characteristic of compact stars and it is shown that the effect of the anisotropy generates that the speed of the radial sound can behave as a function monotonically increasing or monotonically decreasing.

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.

scholarly journals A new class of analytical solutions describing anisotropic neutron stars in general relativity

2021 ◽  
pp. 2150091
Author(s):  
Jay Solanki ◽  
Bhashin Thakore
Keyword(s):  
General Relativity ◽  
Neutron Stars ◽  
Analytical Solutions ◽  
Radial Pressure ◽  
Compact Stars ◽  
Theory Of Relativity ◽  
Field Equations ◽  
Inherent Anisotropy ◽  
Anisotropic Matter ◽  
New Class

A new class of solutions describing analytical solutions for compact stellar structures has been developed within the tenets of General Relativity. Considering the inherent anisotropy in compact stars, a stable and causal model for realistic anisotropic neutron stars was obtained using the general theory of relativity. Assuming a physically acceptable nonsingular form of one metric potential and radial pressure containing the curvature parameter [Formula: see text], the constant [Formula: see text] and the radius [Formula: see text], analytical solutions to Einstein’s field equations for anisotropic matter distribution were obtained. Taking the value of [Formula: see text] as −0.44, it was found that the proposed model obeys all necessary physical conditions, and it is potentially stable and realistic. The model also exhibits a linear equation of state, which can be applied to describe compact stars.

scholarly journals Quintessences compact star with Durgapal potential

2020 ◽  
Vol 35 (17) ◽  
pp. 2050144 ◽  
Author(s):  
Gabino Estevez-Delgado ◽  
Joaquin Estevez-Delgado ◽  
Aurelio Tamez Murguía ◽  
Rafael Soto-Espitia ◽  
Arthur Cleary-Balderas
Keyword(s):  
Compact Star ◽  
Radial Pressure ◽  
State Equation ◽  
Central Density ◽  
Star Model ◽  
Tangential Pressure ◽  
State Equations ◽  
Ordinary Matter ◽  
Linear State ◽  
Anisotropic Pressures

A compact star model formed by quintessence and ordinary matter is presented, both sources have anisotropic pressures and are described by linear state equations, also the state equation of the tangential pressure for the ordinary matter incorporates the effect of the quintessence. It is shown that depending on the compactness of the star [Formula: see text] the constant of proportionality [Formula: see text] between the density of the ordinary matter and the radial pressure, [Formula: see text], has an interval of values which is consistent with the possibility that the matter is formed by a mixture of particles like quarks, neutrons and electrons and not only by one type of them. The geometry is described by the Durgapal metric for [Formula: see text] and each one of the pressures and densities is positive, finite and monotonic decreasing, as well as satisfying the condition of causality and of stability [Formula: see text], which makes our model physically acceptable. The maximum compactness that we have is [Formula: see text], so we can apply our solution considering the observational data of mass and radii [Formula: see text], [Formula: see text] km which generate a compactness [Formula: see text] associated to the star PSR J0348[Formula: see text]+[Formula: see text]0432. In this case, the interval of [Formula: see text] and its maximum central density [Formula: see text] and in the surface [Formula: see text] of the star are [Formula: see text] and [Formula: see text], respectively, meanwhile the central density of the quintessence [Formula: see text].

scholarly journals Chaplygin strange stars in presence of quintessence

2021 ◽  
Vol 36 (29) ◽  
Author(s):  
Joaquin Estevez-Delgado ◽  
Modesto Pineda Duran ◽  
Arthur Cleary-Balderas ◽  
Noel Enrique Rodríguez Maya ◽  
José Martínez Peña
Keyword(s):  
Radial Pressure ◽  
State Equation ◽  
Stellar Model ◽  
Maximum Density ◽  
Spherically Symmetric ◽  
Tangential Pressure ◽  
Strange Stars ◽  
Ordinary Matter ◽  
Anisotropic Pressures ◽  
Symmetric Spacetime

Starting from a regular, static and spherically symmetric spacetime, we present a stellar model formed by two sources of ordinary and quintessence matter both with anisotropic pressures. The ordinary matter, with density [Formula: see text], is formed by a fluid with a state equation type Chaplygin [Formula: see text] for the radial pressure. And the quintessence matter, with density [Formula: see text], has a state equation [Formula: see text] for the radial pressure and [Formula: see text] for the tangential pressure with [Formula: see text]. The model satisfies the required conditions to be physically acceptable and additionally the solution is potentially stable, i.e. [Formula: see text] according to the cracking concept, and it also satisfies the Harrison–Zeldovich–Novikov criteria. We describe in a graphic manner the behavior of the solution for the case in which the mass is [Formula: see text] and radius [Formula: see text][Formula: see text]km which matches the star EXO 1785-248, from where we obtain the maximum density [Formula: see text] for the values of the parameters [Formula: see text], [Formula: see text].

scholarly journals Dynamics of anisotropic collapsing spheres in Einstein Gauss–Bonnet gravity

2015 ◽  
Vol 30 (08) ◽  
pp. 1550038 ◽  
Author(s):  
G. Abbas ◽  
M. Zubair
Keyword(s):  
Dynamical System ◽  
Proper Time ◽  
Vacuum Solution ◽  
Radial Pressure ◽  
The Self ◽  
Junction Conditions ◽  
Field Equations ◽  
Dynamical Equations ◽  
Bonnet Gravity ◽  
Anisotropic Source

This paper is devoted to investigate the dynamics of the self-gravitating adiabatic and anisotropic source in 5D Einstein Gauss–Bonnet gravity. To this end, the source has been taken as Tolman–Bondi model which preserve inhomogeneity in nature. The field equations, Misner–Sharp mass and dynamical equations have formulated in Einstein Gauss–Bonnet gravity in 5D. The junction conditions have been explored between the anisotropic source and vacuum solution in Gauss–Bonnet gravity in detail. The Misner and Sharp approach has been applied to define the proper time and radial derivatives. Further, these helps to formulate general dynamical equations. The equations show that the mass of the collapsing system increases with the same amount as the effective radial pressure increases. The dynamical system preserves retardation which implies that system under-consideration goes to gravitational collapse.

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.

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