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Dynamics of an anisotropic universe is studied in $f(R,T)$ gravity using a rescaled functional $f(R,T)$. Three models have been constructed assuming a power law expansion of the universe. Physical features of the models are discussed. The…

General Relativity and Quantum Cosmology · Physics 2018-06-06 B. Mishra , S. Tarai , S. K. Tripathy

The main purpose of this paper is to investigates structure scalars in the context of $f(\mathcal{G}, T)$ gravity, where $\mathcal{G}$ is the Gauss-Bonnet invariant and $T$ is the trace of stress energy tensor. For this aim, we have…

General Relativity and Quantum Cosmology · Physics 2018-04-05 M. Farasat Shamir , M. Awais Sadiq

Here we have considered the effects of shallowness of the domain as well as the air-water free surface on the stratified shear instabilities of the fluid underneath. First, we numerically solve the non-Boussinesq Taylor-Goldstein equation…

Fluid Dynamics · Physics 2020-03-11 Mihir H. Shete , Anirban Guha

We consider diagonal cylindrically symmetric metrics, with an interior representing a general non-rotating fluid with anisotropic pressures. An exterior vacuum Einstein-Rosen spacetime is matched to this using Darmois matching conditions.…

General Relativity and Quantum Cosmology · Physics 2009-11-06 A. di Prisco , L. Herrera , M. A. H. MacCallum , N. O. Santos

The instabilities arising in a one-dimensional beam sustained by the diffusive photorefractive nonlinearity in out-of-equilibrium ferroelectrics are theoretically and numerically investigated. In the "scale-free model", in striking contrast…

Optics · Physics 2012-01-19 Viola Folli , Eugenio DelRe , Claudio Conti

We present a class of exact solutions of Einstein field equations for a shear-free spherically symmetric anisotropic fluid undergoing radial heat flow. The interior metric fulfilled all the relevant physical and thermodynamic conditions and…

General Relativity and Quantum Cosmology · Physics 2016-01-21 B. C. Tewari , Kali Charan

The main objective of this paper is to investigate the impact of $f(\mathcal{Q},\mathcal{T})$ gravity on the geometry of anisotropic compact stellar objects, where $\mathcal{Q}$ is non-metricity and $\mathcal{T}$ is the trace of the…

General Relativity and Quantum Cosmology · Physics 2024-02-21 M. Zeeshan Gul , M. Sharif , Adeeba Arooj

This paper studies the viable regions of some cosmic models in a higher derivative $f(R,\square R, T)$ theory with the help of energy conditions (where $R$ and $T$ are the Ricci scalar, and trace of energy momentum tensor, respectively).…

General Relativity and Quantum Cosmology · Physics 2020-03-03 M. Ilyas , Z. Yousaf , M. Z. Bhatti

Within the context of modified gravity and dark energy scenarios of the accelerating universe, we study the stability of de Sitter space with respect to inhomogeneous perturbations using a gauge-independent formalism. In modified gravity…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Valerio Faraoni

We use a modified Einstein-Maxwell gravity to study stability of an electrostatic spherical star. Correction terms in this model are scalers which are made from contraction of Ricci tensor and electromagnetic vector potential. Our…

General Relativity and Quantum Cosmology · Physics 2023-12-05 Hossein Ghaffarnejad , Tohid Ghorbani , Firoozeh Eidizadeh

We study the stability of neutron stars with toroidal magnetic fields by magnetohydrodynamic simulation in full general relativity under assumption of axial symmetry. Nonrotating and rigidly rotating neutron stars are prepared for a variety…

Astrophysics · Physics 2008-12-18 Kenta Kiuchi , Masaru Shibata , Shijun Yoshida

The effect of magnetic shear and shear flow on local gravitationally induced instabilities is investigated. A simple model is constructed allowing for an arbitrary entropy gradient and a shear plasma flow in the Boussinesq approximation. A…

Astrophysics · Physics 2009-11-06 Gregory G. Howes , Steven C. Cowley , James C. McWilliams

Shear flows have an important impact on the dynamics in an assortment of different astrophysical objects including accreditation discs and stellar interiors. Investigating shear flow instabilities in a polytropic atmosphere provides a…

Solar and Stellar Astrophysics · Physics 2015-05-06 V. Witzke , L. J. Silvers , B. Favier

We consider static neutron stars within the framework of $R^2$ gravity. The neutron fluid is described by three different types of realistic equations of state (soft, moderately stiff, and stiff). Using the observational data on the neutron…

General Relativity and Quantum Cosmology · Physics 2018-06-08 Vladimir Folomeev

This paper deals with existence of strange stars in $f\left(T\right) $ modified gravity. For this purpose, we have taken the diagonal tetrad field of static spacetime with charged anisotropic fluid and MIT bag model, which provide the…

General Physics · Physics 2016-06-28 G. Abbas , Shahid Qaisar , Abdul Jawad

We investigate various anisotropic spherical distributions of charged celestial bodies within the context of f(R) gravity, where R represents the Ricci scalar. The properties of specific charged compact objects are analyzed by using the…

General Relativity and Quantum Cosmology · Physics 2025-05-13 W. U. Rahman , M. Ilyas , Yi Zhong , De-Liang Yao

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…

General Relativity and Quantum Cosmology · Physics 2019-10-28 Muhammad Asad Saeed , Ifra Noureen

In this paper, we explore instability regions of non-static axial reflection symmetric spacetime with anisotropic source in the interior. We impose linear perturbation on the Einstein field equations and dynamical equations to establish the…

General Physics · Physics 2015-12-16 M. Sharif , M. Zaeem Ul Haq Bhatti

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 $f(R) = R + \alpha R^2$, which incorporates…

General Relativity and Quantum Cosmology · Physics 2025-11-18 A. Zahra , S. A. Mardan , Muhammad Bilal Riaz , Javlon Rayimbaev , Inomjon Ibragimov , Munisbek Akhmedov , Erkaboy Davletov

Unitarity of evolution in gravitational collapses implies existence of macroscopic stable horizonless objects. With such objects in mind, we study the effects of anisotropy of pressures on the stability of stars. We consider stars in four…

High Energy Physics - Theory · Physics 2015-10-05 S. Kalyana Rama