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We establish a well-posedness theory for the f(R) theory of modified gravity, which is a generalization of Einstein's theory of gravitation. The scalar curvature R of the spacetime, which arises in the integrand of the Einstein-Hilbert…

Analysis of PDEs · Mathematics 2014-12-30 Philippe G. LeFloch , Yue Ma

In this review we briefly summarize the so-called effective fluid approach, which is a compact framework that can be used to describe a plethora of different modified gravity models as general relativity (GR) and a dark energy (DE) fluid.…

Cosmology and Nongalactic Astrophysics · Physics 2023-02-03 Savvas Nesseris

This article belongs to a series where the influence of anisotropic pressure on the gravitational properties of rigidly rotating fluids is studied using new exactsolutions of GR constructed for the purpose. For mathematical simplification,…

General Relativity and Quantum Cosmology · Physics 2023-08-08 Marie-No\''elle Célérier

In this work we will analyse the complexity factor, proposed by L. Herrera, for spherically symmetric static matter distributions satisfying a polytropic equation through the gravitational decoupling method. Specifically, we will use the…

General Relativity and Quantum Cosmology · Physics 2022-11-04 C. Las Heras , P. Leon

We present a novel fitting formula for the halo concentration enhancement in chameleon $f(R)$ gravity relative to General Relativity (GR). The formula is derived by employing a large set of $N$-body simulations of the Hu-Sawicki $f(R)$…

Cosmology and Nongalactic Astrophysics · Physics 2019-06-04 Myles A. Mitchell , Christian Arnold , Jian-hua He , Baojiu Li

In this paper, we examine static spherically symmetric wormhole solutions in generalized $f(R,\phi)$ gravity. To do this, we consider three different kinds of fluids: anisotropic, barotropic and isotropic. We explore different $f(R,\phi)$…

General Relativity and Quantum Cosmology · Physics 2018-12-19 M. Zubair , Farzana Kousar , Sebastian Bahamonde

Recently, a generalized gravity theory was proposed by Harko etal where the Lagrangian density is an arbitrary function of the Ricci scalar R and the trace of the stress-energy tensor T, known as F(R,T) gravity. In their derivation of the…

General Physics · Physics 2015-06-12 Subenoy Chakraborty

We discuss the gravitational collapse of spherical compact objects in the background of $f(R,T,Q)$ theory, where $R$ represent the Ricci scalar, $T$ is the trace of energy momentum tensor while $Q\equiv R_{\mu\nu}T^{\mu\nu}$, and…

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

This paper's main aim is to investigate the existence of a new classification of embedded class-I solutions of compact stars, by using Karmarkar condition in $f(R)$ gravity background. To achieve that goal, we consider two different models…

General Relativity and Quantum Cosmology · Physics 2021-05-07 Tayyaba Naz , Ammara Usman , M. Farasat Shamir

One of the possible potential candidates for describing the universe's rapid expansion is modified gravity. In the framework of the modified theory of gravity $f(R,G)$, the present work features the materialization of anisotropic matter,…

General Relativity and Quantum Cosmology · Physics 2022-06-29 W. U. Rahman , M. Ilyas , Z. Yousaf , S. Ullah , F. Khan , R. khan

We study spherically symmetric gravitational collapse of an inhomogeneous fluid with anisotropic energy momentum tensor (EMT) in Rastall gravity. Considering a linear equation of state (EoS) for the fluid profiles, i.e., $p_r=w_r\rho$ and…

General Relativity and Quantum Cosmology · Physics 2026-04-28 Akbar Jahan , Naser Sadeghnezhad , Amir Hadi Ziaie

An anisotropic fluid with variable energy density and negative pressure is proposed, both outside and inside stars. The gravitational field is constant everywhere in free space (if we neglect the local contributions) and its value is of the…

General Relativity and Quantum Cosmology · Physics 2015-05-27 Hristu Culetu

By applying the symmetric and trace-free formalism in terms of the irreducible Cartesian tensors, the metric for the external gravitational field of a spatially compact stationary source is provided in $F(X,Y,Z)$ gravity, a generic…

General Relativity and Quantum Cosmology · Physics 2023-11-15 Bofeng Wu , Chao-Guang Huang

Recently we showed that in FLRW cosmology, the contribution from higher curvature terms in any generic metric gravity theory to the energy-momentum tensor is of the perfect fluid form. Such a geometric perfect fluid can be interpreted as a…

General Relativity and Quantum Cosmology · Physics 2024-08-07 Metin Gürses , Yaghoub Heydarzade , Çetin Şentürk

In this paper we study the equilibrium configurations of anisotropic self-gravitating fermions, by extending to general relativity the solutions obtained in a previous paper. This treatment also generalizes to anisotropic systems the…

Astrophysics of Galaxies · Physics 2015-07-23 Marco Merafina , Giuseppe Alberti

The manifesto of the current article is to investigate the compact anisotropic matter profiles in the context of one of the modified gravitational theories, known as $f(\mathcal{R}, \mathcal{T})$ gravity, where $\mathcal{R}$ is a Ricci…

General Relativity and Quantum Cosmology · Physics 2021-01-05 G. Mustafa , Xia Tie-Cheng , Mushtaq Ahmad , M. Farasat Shamir

In this paper, we study the dynamical irregularity of the locally anisotropic spherical fluids in the context of Einstein-Gauss-Bonnet theory. We aim to describe the causes of energy-density irregularity of self-gravitating fluids and…

General Relativity and Quantum Cosmology · Physics 2025-09-03 Z. Yousaf , Kazuharu Bamba , Mansoor Alshehri , A. Farhat

Analytical $f(R)$-gravity models introduce Yukawa-like corrections to the Newtonian potential in the weak field limit. These models can explain the dynamics of galaxies and cluster of galaxies without requiring dark matter. To test the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 I. De Martino , M. De Laurentis , F. Atrio-Barandela , S. Capozziello

In this work, following our recent findings in [1], we extend our analysis to explore the generalization of spherically symmetric and static black-bounce solutions, known from General Relativity, within the framework of the $f(R)$ theory in…

General Relativity and Quantum Cosmology · Physics 2025-12-19 Marcos V. de S. Silva , T. M. Crispim , G. Alencar , R. R. Landim , Manuel E. Rodrigues

The main goal of this work is to provide a comprehensive study of relativistic structures in the context of recently proposed {$\mathcal{R}+ \alpha \mathcal{A}$} gravity, where $\mathcal{R}$ is the Ricci scalar, and $\mathcal{A}$ is the…

General Relativity and Quantum Cosmology · Physics 2023-04-11 M. Farasat Shamir , Eesha Meer