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S. A. Mardan

Publications and source records attributed to S. A. Mardan.

9 recordsLinked to original sources

Dynamics of Charged Radiating Collapse with Shear and Anisotropy

We investigate a charged anisotropic radiating stellar configuration undergoing gravitational collapse in the presence of shear and heat flux within the Einstein Maxwell framework. The interior spacetime is described by a time dependent spherically symmetric geometry and is matched to an exterior charged Vaidya spacetime. The electromagnetic field is incorporated explicitly through Maxwell equations, allowing the electric charge to contribute to the matter variables, mass function, and boundary evolution. The charged junction condition is reduced to a Riccati type differential equation with suitable transformations and exact solution is obtained. The physical properties of the resulting shearing solution are examined through the energy density, radial and tangential pressures, pressure anisotropy, heat flux, electric charge, energy conditions, sound speeds, Herrera cracking criterion, and complexity factor. The energy density and radial pressure remain positive and decrease towards the stellar surface, whereas the tangential pressure remains negative, confirming the anisotropic character of the configuration. Heat transport and electromagnetic effects are strongest in the inner stellar region. The energy and causality conditions are satisfied. The cracking function indicates potential stability against cracking. The complexity factor remains positive, with electric charge providing an additional contribution alongside pressure anisotropy, density inhomogeneity, and dissipative heat flux. These results provide a comprehensive picture of the physical behavior and internal structure of the charged shearing radiative collapse model.

gr-qc

Nonlinear evolution of anisotropic matter configurations under higher-order curvature corrections

This study examines the dynamical evolution of self-gravitating systems in the presence of exotic matter within the framework of $f(R)$ gravity. Specifically, we have adopted the Starobinsky model $f(R) = R + αR^2$, which incorporates higher-order curvature corrections to describe nonlinear gravitational behavior. The analysis focuses on the nonlinear spherical evolution of anisotropic matter configurations and explains how dark matter influences their physical characteristics. The presence of dark matter is found to significantly affect the radial and tangential pressure distributions, thereby altering the overall dynamics of the system. The model is employed for the compact object $ Her~X-1$ described by the generalized Tolman-Kuchowicz metric, demonstrating a singularity-free behavior of the physical parameters. The results reveal that increasing the parameter $n$ of the generalized Tolman-Kuchowicz metric leads to striking variations in the model characteristics, highlighting its essential role in governing internal structure and evolution of the compact object. The model remains physically viable under different testing criteria like energy conditions, hydrostatic equilibrium condition, adiabatic index, causality conditions, Herrera's Cracking condition and mass-radius relation presented in this work.

gr-qc

Modeling Compact Objects in $f(R)$ Gravity: Application of Buchdahl-I Metric with Chaplygin Equation of State

This paper investigates realistic anisotropic matter configurations for spherical symmetry in the framework of $f(R)$ gravity. The solutions obtained from Buchdahl-I metric are used to determine the behavior of PSR J0740+6620, PSR J0348+0432 and 4U 1608-52 with Starobinsky model. Analysis of physical parameters such as density, pressure, and anisotropy is illustrated through graphs, and the stability of compact objects is investigated by energy and causality conditions. We will also discuss the behavior of gravitational, hydrostatic and anisotropic forces, gravitational redshift and adiabatic index. At the theoretical and astrophysical scales, the graphical representations validate the practical and realistic $f(R)$ gravity models.

gr-qc

Development of complexity induced frameworks for charged cylindrical polytropes

The main theme of this work is the development of complexity induced generalized frameworks for static cylindrical polytropes. We consider two different definitions of generalized polytopes with charged anisotropic inner fluid distribution. A new methodology based on complexity factor for the generation of consistent sets of differential equations will be presented. We conclude our work by carrying out graphical analysis of developed frameworks.

gr-qc

Cracking of Charged Polytropes with Generalized Polytropic Equation of State

We discuss the occurrence of cracking in charged anisotropic polytropes with generalized polytropic equation of state through two different assumptions; (i) by carrying out local density perturbations under conformally flat condition (ii) by perturbing anisotropy, polytropic index and charge parameters. For this purpose, we consider two different definitions of polytropes exist in literature. We conclude that under local density perturbations scheme cracking does not appears in both types of polytropes and stable configuration are observed, while with second kind of perturbation cracking appears in both types of polytropes under certain conditions.

physics.gen-ph

On Cracking of Charged Anisotropic Polytropes

Recently in \cite{34}, the role of electromagnetic field on the cracking of spherical polytropes has been investigated without perturbing charge parameter explicitly. In this study, we have examined the occurrence of cracking of anisotropic spherical polytropes through perturbing parameters like anisotropic pressure, energy density and charge. We consider two different types of polytropes in this study. We discuss the occurrence of cracking in two different ways $(i)$ by perturbing polytropic constant, anisotropy and charge parameter $(ii)$ by perturbing polytropic index, anisotropy and charge parameter for each case. We conclude that cracking appears for a wide range of parameters in both cases. Also, our results are reduced to \cite{33} in the absence of charge.

physics.gen-ph

Charged Cylindrical Polytropes with Generalized Polytropic Equation of State

We study the general formalism of polytropes in relativistic regime with generalized polytropic equations of state in the vicinity of cylindrical symmetry. We take charged anisotropic fluid distribution of matter with conformally flat condition for the development of general framework of polytropes. We discussed the stability of the model by Whittaker formula and concluded that one of the developed model is physically viable.

physics.gen-ph

Study of polytropes with Generalized polytropic Equation of State

The aim of this paper is to discuss the theory of Newtonian and relativistic polytropes with generalized polytropic equation of state. For this purpose, we formulated the general framework to discuss the physical properties of polytrops with anisotropic inner fluid distribution under conformally flat condition in the presence of charge. We investigate the stability of these polytrops in the vicinity of generalized polytropic equation through Tolman-mass. It is concluded that one of the derived models is physically acceptable.

physics.gen-ph

Fate of Electromagnetic Field on the Cracking of PSR J1614-2230 in Quadratic Regime

In this paper, we study the cracking of compact object PSR J1614-2230 in quadratic regime with electromagnetic field. For this purpose, we develop a general formalism to determine the cracking of charged compact objects. We apply the local density perturbations to the hydrostatic equilibrium equation as well as all the physical variables involve in the model. We plot the force distribution function against radius of the star with different values of model parameters both with and without charge. It is found that PSR J1614-2230 remains stable (no cracking) corresponding to different values of parameters when charge is zero, while it exhibit cracking (unstable) when charge is introduced. We conclude that stability region increases as amount of charge increases.

gr-qc