arXiv subjects

Ifra Noureen

Publications and source records attributed to Ifra Noureen.

14 recordsLinked to original sources

arXiv2019

Effect of Electromagnetism upon the Collapse of Cylindrical Symmetric Stars in f(R; T) Gravity

By the end of the evaluation of this research artifact, readers would be able to describe the effect of conducted plasma on evolution of stellar objects. In this script, we have analyzed the stability of charged cylindrically symmetric stellar objects in the context of f(R; T) theory of gravity. We have fabricated field equations and their conforming dynamical equations and then we have used perturbation scheme for additional analysis. Adiabatic index Γ has been used to sort inequalities in the Newtonian and the post Newtonian regimes. At the end we caught some extra limitations due to which we have concluded that effect of charge on star upsurges its instability

gr-qc↗

arXiv2017

Dynamical Analysis of Cylindrically Symmetric Anisotropic Sources in $f(R,T)$ Gravity

In this paper, we have analyzed the stability of cylindrically symmetric collapsing object filled with locally anisotropic fluid in $f(R,T)$ theory, where $R$ is the scalar curvature and $T$ is the trace of stress-energy tensor of matter. Modified field equations and dynamical equations are constructed in $f(R,T)$ gravity. Evolution or collapse equation is derived from dynamical equations by performing linear perturbation on them. Instability range is explored in both Newtonian and post-Newtonian regimes with the help of adiabetic index, which defines the impact of physical parameters on the instability range. Some conditions are imposed on physical quantities to secure the stability of the gravitating sources.

physics.gen-ph↗

arXiv2016

Axially Symmetric Shear-free Fluids in $f(R,T)$ Gravity

In this work we have discussed the implications of shear-free condition on axially symmetric anisotropic gravitating objects in $f(R,T)$ theory. Restricted axial symmetry ignoring rotation and reflection enteries is taken into account for establishment of instability range. Implementation of linear perturbation on constitutive modified dynamical equations yield evolution equation. This equation associates adiabatic index $Γ$ with material and dark source components defining stable and unstable regions in Newtonian (N) and post-Newtonian (pN) approximations.

gr-qc↗

arXiv2015

Possible Formation of Compact Stars in $f(R,T)$ Gravity

This paper constitutes the investigations regarding possible formation of compact stars in $f(R,T)$ theory of gravity, where $R$ is Ricci scalar and $T$ is trace of energy momentum tensor. In this connection, we use analytic solution of Krori and Barua metric (Krori and Barua 1975)to spherically symmetric anisotropic star in context of $f(R,T)$ gravity. The masses and radii of compact stars models namely model $1$, model$ 2$ and model $3$ are employed to incorporate with unknown constants in Krori and Barua metric. The physical features such as regularity at center, anisotropy measure, casuality and well-behaved condition of above mentioned class of compact starts are analyzed. Moreover, we have also discussed energy conditions, stability and surface redshift in $f(R,T)$ gravity.

physics.gen-ph↗

arXiv2015

Dynamical Analysis of Charged Anisotropic Spherical Star in f(R) Gravity

We consider a modified gravity theory, $f(R)=R+αR^n-\frac{μ^4}{R^m}$, in the metric formulation and analyze the contribution of electromagnetic field on the range of dynamical instability of a star filled with anisotropic matter. The collapse equation is developed by applying conservation on anisotropic matter, Maxwell source and dark source terms arising due to $f(R)$ gravity. Specific perturbation scheme is implemented and it is observed that the inclusion of Maxwell source slows down the collapse and makes system more stable in Newtonian regime. Also, we make comparison of our results with the existing literature.

physics.gen-ph↗

arXiv2015

Hot Plasma Modes Across Reissner-Nordstrom de Sitter Horizon in a Veselago Medium

In this manuscript, wave attributes of hot plasma around Reissner- Nordstrom-de Sitter (RN-dS) metric in a Veselago medium are in- vestigated. General relativistic magnetohydrodynamical (GRMHD) equations in planar coordinates for the RN-dS horizon are reformulated by implementation of ADM 3+1 technique. Further, perturba- tion scheme is used to arrive at linearly perturbed GRMHD equations whose component form is used to attain dispersion relations for rotating (non-magnetized and magnetized) plasma. Wave propagation in hot plasma is explained by three dimensional graphical representation of the wave number, refractive index, its change with respect to angular velocity, phase and group velocities. Finally, comparison of wave properties is presented, results reassert the presence of Veselago medium.

gr-qc↗

arXiv2015

Shearfree Condition and dynamical Instability in $f(R,T)$ gravity

The implications of shearfree condition on instability range of anisotropic fluid in $f(R,T)$ are studied in this manuscript. A viable $f(R, T)$ model is chosen to arrive at stability criterion, where $R$ is Ricci scalar and $T$ is the trace of energy momentum tensor. The evolution of spherical star is explored by employing perturbation scheme on modified field equations and contracted Bianchi identities in $f(R, T)$. The effect of imposed shearfree condition on collapse equation and adiabatic index $Γ$ is studied in Newtonian and post-Newtonian regimes.

gr-qc↗

arXiv2015

Evolution of Axially Symmetric Anisotropic Sources in $f(R,T)$ Gravity

We discuss the dynamical analysis in $f(R,T)$ gravity (where $R$ is Ricci scalar and $T$ is trace of energy momentum tensor) for gravitating sources carrying axial symmetry. The self gravitating system is taken to be anisotropic and line element describes axially symmetric geometry avoiding rotation about symmetry axis and meridional motions (zero vorticity case). The modified field equations for axial symmetry in $f(R,T)$ theory are formulated, together with the dynamical equations. Linearly perturbed dynamical equations lead to the evolution equation carrying adiabatic index $Γ$ that defines impact of non-minimal matter to geometry coupling on range of instability for Newtonian (N) and post-Newtonian (pN) approximations.

gr-qc↗

arXiv2015

Dynamical Instability and Expansion-free Condition in $f(R,T)$ Gravity

Dynamical analysis of spherically symmetric collapsing star surrounding in locally anisotropic environment with expansion-free condition is presented in $f(R,T)$ gravity, where $R$ corresponds to Ricci scalar and $T$ stands for the trace of energy momentum tensor. The modified field equations and evolution equations are reconstructed in the framework of $f(R,T)$ gravty. In order to acquire the collapse equation we implement the perturbation on all matter variables and dark source components comprising the viable $f(R,T)$ model. The instability range is described in Newtonian and post-Newtonian eras by constraining the adiabatic index $Γ$ to maintain viability of considered model and stable stellar configuration.

gr-qc↗

arXiv2015

Impact of Extended Starobinsky Model on Evolution of Anisotropic, Vorticity-free Axially Symmetric Sources

We study the implications of $R^n$ extension of Starobinsky model on dynamical instability of Vorticity-free axially symmetric gravitating body. The matter distribution is considered to be anisotropic for which modified field equations are formed in context of $f(R)$ gravity. In order to achieve the collapse equation, we make use of the dynamical equations, extracted from linearly perturbed contracted Bianchi identities. The collapse equation carries adiabatic index $Γ$ in terms of usual and dark source components, defining the range of stability/insatbility in Newtonian (N) and post-Newtonian (pN) eras. It is found that supersymmetric supergravity $f(R)$ model represents the more practical substitute of higher order curvature corrections.

gr-qc↗

arXiv2014

Dynamical Instability of Spherical Star in $f(R,T)$ gravity

This work is based on stability analysis of spherically symmetric collapsing star surrounding in locally anisotropic environment in $f(R,T)$ gravity, where $R$ is Ricci scalar and $T$ corresponds to the trace of energy momentum tensor. Field equations and dynamical equations are presented in the context of $f(R,T)$ gravity. Perturbation schem is employed on dynamical equations to find the collapse equation. Furthermore, condition on adiabatic index $Γ$ is constructed for Newtonian and post-Newtonian eras to address instability problem. Some constraints on physical quantities are imposed to maintain stable stellar configuration. The results in this work are in accordance with $f(R)$ gravity for specific case.

physics.gen-ph↗

arXiv2014

Dissipative Spherical Collapse of Charged Anisotropic Fluid in f(R) Gravity

This manuscript is devoted to study the combined effect of a viable model, f(R) = R + αR^n, and electromagnetic field on the instability range of gravitational collapse. We assume charged anisotropic fluid that dissipate energy via heat flow and discuss that electromagnetic field, density inhomogeneity, shear and phase transition on astrophysical bodies can be incorporated by locally anisotropic background. Dynamical equations help to investigate the evolution of self-gravitating objects and leads to the conclusion that adiabatic index depend upon the electromagnetic background, mass and radius of the spherical objects.

gr-qc↗

arXiv2011

Isothermal Plasma Wave Properties of the Schwarzschild de-Sitter Black Hole in a Veselago Medium

In this paper, we study wave properties of isothermal plasma for the Schwarzschild de-Sitter black hole in a Veselago medium. We use ADM 3+1 formalism to formulate general relativistic magnetohydrodynamical (GRMHD) equations for the Schwarzschild de-Sitter spacetime in Rindler coordinates. Further, Fourier analysis of the linearly perturbed GRMHD equations for the rotating (non-magnetized and magnetized) background is taken whose determinant leads to a dispersion relation. We investigate wave properties by using graphical representation of the wave vector, the refractive index, change in refractive index, phase and group velocities. Also, the modes of wave dispersion are explored. The results indicate the existence of the Veselago medium.

physics.gen-ph↗

arXiv2011

Dispersion Modes of Hot Plasma for Schwarzschild de-Sitter Horizon in a Veselago Medium

We analyze the dispersion modes of hot plasma around Schwarzschild de-Sitter event horizon in the presence of Veselago medium. For this purpose, we apply ADM 3+1 formalism to develop GRMHD equations for the Schwarzschild de-Sitter spacetime. Implementation of linear perturbation yields perturbed GRMHD equations that are used for the Fourier analysis of rotating (non-magnetized and magnetized) plasma. Wave analysis is described by the graphical representation of the wave vector, refractive index, change in refractive index, phase and group velocities. The outcome of this work supports the validity of Veselago medium.

physics.gen-ph↗