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The atmospheres of planets (including Earth) and the outer layers of stars have often been treated in radiative transfer as plane-parallel media, instead of spherical shells, which can lead to inaccuracy, e.g. limb darkening. We give an…

Statistical Mechanics · Physics 2009-11-11 Michael J. Caola

A scenario of an emergent universe is constructed in the background of an inhomogeneous space-time model which is asymptotically (at spatial infinity) FRW space-time. The cosmic substratum consists of non-interacting two components, namely…

General Relativity and Quantum Cosmology · Physics 2016-01-18 Subhra Bhattacharya , S. Chakraborty

Isotropic and spatially homogeneous viscous fluid cosmological models are investigated using the truncated Israel-Stewart theory of irreversible thermodynamics to model the bulk viscous pressure. The governing system of differential…

General Relativity and Quantum Cosmology · Physics 2010-04-06 A A Coley , R J van den Hoogen

Starting with the relativistic Boltzmann equation where the collision term is generalized to include nonlocal effects via gradients of the phase-space distribution function, and using Grad's 14-moment approximation for the distribution…

Nuclear Theory · Physics 2013-05-23 Amaresh Jaiswal , Rajeev S. Bhalerao , Subrata Pal

We investigate the out-of-equilibrium dynamics of viscous fluids in a spatially flat Friedmann-Lema\^itre-Robertson-Walker cosmology using the most general causal and stable viscous energy-momentum tensor defined at first order in spacetime…

General Relativity and Quantum Cosmology · Physics 2023-07-31 Fábio S. Bemfica , Marcelo M. Disconzi , Jorge Noronha , Robert J. Scherrer

Astrophysical plasmas are subject to a tight connection between magnetic fields and the diffusion of particles, which leads to an anisotropic transport of energy. Under the fluid assumption, this effect can be reduced to an…

Astrophysics of Galaxies · Physics 2016-01-13 Yohan Dubois , Benoît Commerçon

Considering charged fluid spheres as anisotropic sources and the diffusion limit as the transport mechanism, we suppose that the inner space--time admits self--similarity. Matching the interior solution with the…

General Relativity and Quantum Cosmology · Physics 2016-08-16 W. Barreto , B. Rodríguez , L. Rosales , O. Serrano

We apply the postquasistatic approximation to study the evolution of spherically symmetric fluid distributions undergoing dissipation in the form of radial heat flow. For a model which corresponds to an incompressible fluid departing from…

General Relativity and Quantum Cosmology · Physics 2014-11-21 B. Rodríguez-Mueller , C. Peralta , W. Barreto , L. Rosales

Combining the equivalence between cosmological particle creation and an effective viscous fluid pressure with the fact that the latter represents a dynamical degree of freedom within the second-order Israel-Stewart theory for imperfect…

Astrophysics · Physics 2009-10-31 Winfried Zimdahl

Two distinct non-singular interior models that describe anisotropic spherical configurations are presented in this work. We develop the Einstein field equations and the associated mass function in accordance with a static spherical…

General Relativity and Quantum Cosmology · Physics 2025-10-10 M. Sharif , Tayyab Naseer , Hira Shadab

It is well known that Kasner-type cosmologies provide a useful framework for analyzing the three-dimensional anisotropic expansion because of the simplification of the anisotropic dynamics. In this paper relativistic multi-fluid Kasner-type…

General Relativity and Quantum Cosmology · Physics 2015-03-17 Mauricio Cataldo , Fabiola Arevalo , Patricio Mella

Purpose: This essay is a retelling of general relativity in a language in which space-time geometry is expressed as a fluid. This trivial and useful reformulation gives 1) a non-perturbative covariant description of cosmological…

General Physics · Physics 2026-01-27 Albert Stebbins

We investigate the anisotropic evolution of spacetime driven by perfect fluid with off-diagonal shear-viscosity components. We consider the simplest form of the equation of state for fluid, for which the pressure and the shear stress are…

General Relativity and Quantum Cosmology · Physics 2023-12-25 Inyong Cho , Rajibul Shaikh

In this paper we study the consistency of a cosmological model representing a universe filled with a one-component dissipative dark matter fluid, in the framework of the causal Israel-Stewart theory, where a general expression arising from…

General Relativity and Quantum Cosmology · Physics 2020-11-24 Norman Cruz , Esteban González , Guillermo Palma

The thermodynamic interpretation of the Stephani Universes is studied in detail. The general expression of the speed of sound and of the thermodynamic schemes associated with a thermodynamic solution is obtained. The constraints imposed on…

General Relativity and Quantum Cosmology · Physics 2024-09-04 Salvador Mengual , Joan Josep Ferrando , Juan Antonio Sáez

The arrival directions of TeV-PeV cosmic rays are remarkably uniform due to the isotropization of their directions by scattering on turbulent magnetic fields. Small anisotropies can exist in standard diffusion models, however, only on the…

High Energy Astrophysical Phenomena · Physics 2022-03-14 Marco Kuhlen , Vo Hong Minh Phan , Philipp Mertsch

A numerical solution of Einstein field equations for a spherical symmetric and stationary system of identical and auto-gravitating particles in phase transition is presented. The fluid possess a perfect fluid energy momentum tensor, and the…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Jose D. Polanco , Patricio S. Letelier , Maximiliano Ujevic

We consider an isothermal compressible fluid evolving on a cosmological background which may be either expanding or contracting toward the future. The Euler equations governing such a flow consist of two nonlinear hyperbolic balance laws…

Analysis of PDEs · Mathematics 2022-10-12 Yangyang Cao , Mohammad A. Ghazizadeh , Philippe G. LeFloch

Motion of an ultra-relativistic perfect fluid in space-time with the Kasner metrics is investigated by the Hamiltonian method. It is found that in the limit of small times a tendency takes place to formation of strong inhomogeneities in…

General Relativity and Quantum Cosmology · Physics 2014-11-17 V. P. Ruban , D. I. Podolsky

Considering the condition on conservation of energy momentum tensor (EMT), we study late time cosmological solutions in the context of $f(R,T)=R+\alpha T^{n}$ gravity (where $\alpha$ and $n$ are constants) in a flat FLRW spacetime. The…

General Relativity and Quantum Cosmology · Physics 2024-03-06 Hamid Shabani , Norman Cruz , Amir Hadi Ziaie