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This manuscript copes with the issue of analyzing the conditions to check the stability of the pressure isotropy condition by taking into account a spherically symmetric dissipative astrophysical configuration with the Palatini $f(R)$…

General Relativity and Quantum Cosmology · Physics 2021-08-31 Z. Tariq , M. Z. Bhatti , Z. Yousaf

We consider the consequences of applying general relativity to the description of the dynamics of a galaxy, given the observed flattened rotation curves. The galaxy is modeled as a stationary axially symmetric pressure-free fluid. In spite…

Astrophysics · Physics 2010-10-27 F. I. Cooperstock , S. Tieu

We propose a Lorentz-covariant theory of gravity, and explain its theoretical origins in the problem of time in Newtonian physics. In this retarded gravitation theory (RGT), the gravitational force depends upon both retarded position and…

General Physics · Physics 2015-05-27 C. K. Raju

The dynamics of inelastic hard spheres is described in terms of the binary collision expansion, yielding the corresponding pseudo-Liouville equation and BBGKY hierarchy for the reduced distribution functions. Based on cluster expansion…

Statistical Mechanics · Physics 2008-02-03 T. P. C. van Noije , M. H. Ernst

In this paper, we generate an exact anisotropic gravastar model using gravitational decoupling technique through minimal geometric deformation in the framework of $f(\Re, {T}^{2})$ gravity. This novel model explains an ultra-compact stellar…

General Relativity and Quantum Cosmology · Physics 2023-04-17 M. Sharif , Saba Naz

The paper considers a set of equations describing the static isotropic gravity field of a macroscopic body within the framework of the theory of gravity with a constraint. A general approximate solution of these equations is obtained. The…

General Relativity and Quantum Cosmology · Physics 2024-02-08 Alexander P. Sobolev , Aleksey Sobolev

Collapsing solutions in $f(R)$ gravity are restricted due to junction conditions that demand continuity of the Ricci scalar and its normal derivative across the time-like collapsing hypersurface. These are obtained via the method of…

General Relativity and Quantum Cosmology · Physics 2020-10-28 Sandip Chowdhury , Kunal Pal , Kuntal Pal , Tapobrata Sarkar

The basic objective of this investigation is to explore the impact of a novel gravitational modification, specifically, the $f(\mathcal{G}, \mathbf{T}^2)$ (where $\mathbf{T}^2 \equiv T_{\alpha\beta}T^{\alpha\beta}$, $T^{\alpha\beta}$…

General Relativity and Quantum Cosmology · Physics 2022-04-12 Z. Yousaf , M. Z. Bhatti , S. Khan , P. K. Sahoo

Different sequences of ellipsoids are represented on the ellipticity-rotation plane. The rotation parameter is defined as the ratio of kinetic energy related to the mean tangential equatorial velocity component to kinetic energy related to…

Instrumentation and Methods for Astrophysics · Physics 2014-11-20 R. Caimmi

We investigate the classical and quantum dynamics of $f(R)$ gravity's rainbow in the presence of a perfect fluid, employing Schutz's formalism to establish a well-defined notion of time. In the classical regime, we derive and solve the…

General Relativity and Quantum Cosmology · Physics 2025-07-02 Andrés Burton-Villalobos , Giovanni Otalora , Manuel Gonzalez-Espinoza , Yoelsy Leyva

We explore wormhole solutions sourced by Casimir energy density involving generalized uncertainty principle corrections within the framework of Rastall-Rainbow gravity. The questions of traversability and stability, as well as the presence…

General Relativity and Quantum Cosmology · Physics 2024-12-10 Emmanuele Battista , Salvatore Capozziello , Abdelghani Errehymy

We investigate the derivation of Friedmann equations in Rainbow gravity following Jacobson thermodynamic approach. We do not restrict the rainbow functions to be constant as is customarily used, and show that the first law of thermodynamics…

General Relativity and Quantum Cosmology · Physics 2020-05-28 A. Ashour , M. Alcheikh , N. Chamoun

This work is devoted to study the analytical and regular solutions of a particular self-gravitating object (i.e., gravastar) in a particular theory of gravity. We derive the corresponding field equations in the presence of effective energy…

General Relativity and Quantum Cosmology · Physics 2021-08-30 Z. Yousaf , M. Z. Bhatti , H. Asad

In Part I of this study, we analyzed the motion of inertial particles in isotropic turbulence in the absence of gravity using direct numerical simulation (DNS). Here, in Part II, we introduce gravity and study its effect over a wide range…

Fluid Dynamics · Physics 2016-05-25 Peter J. Ireland , Andrew D. Bragg , Lance R. Collins

Amongst a number of modified theories of gravity, the Rastall theory has been propounded to address some shortcomings of the standard theory of general relativity. Our purpose is to investigate this framework's capacity to analyse stellar…

General Relativity and Quantum Cosmology · Physics 2018-07-04 Sudan Hansraj , Ayan Banerjee

In astrophysics, the gravitational stability of a self-gravitating polytropic fluid sphere is an intriguing subject, especially when trying to comprehend the genesis and development of celestial bodies like planets and stars. This stability…

General Relativity and Quantum Cosmology · Physics 2024-07-10 Mohamed S. Aboueisha , A. S. Saad , Mohamed I. Nouh , Tarek M. Kamel , M. M. Beheary , Kamel A. K. Gadallah

When tetrad (metric) fields are not invertible, the standard canonical formulation of gravity cannot be adopted as it is. Here we develop a Hamiltonian theory of gravity for non-invertible tetrad. In contrast to Einstein gravity, this phase…

General Relativity and Quantum Cosmology · Physics 2023-12-13 Sandipan Sengupta

In this paper, we consider static spherical structure to develop some anisotropic solutions by employing the extended gravitational decoupling scheme in the background of…

General Relativity and Quantum Cosmology · Physics 2023-02-10 M. Sharif , Tayyab Naseer

A theory of gravitation is proposed, modeled after the notion of a Ricci flow. In addition to the metric an independent volume enters as a fundamental geometric structure. Einstein gravity is included as a limiting case. Despite being a…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Wolfgang Graf

We solve spherically symmetric radiation flows under full special relativity with the help of a variable Eddington factor $f(\tau, \beta)$, where $\tau$ is the optical depth and $\beta$ is the flow velocity normalized by the speed of light.…

Astrophysics · Physics 2015-05-13 Chizuru Akizuki , Jun Fukue