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In this paper we discuss some consequences of cosmological models in which the primordial cosmic matter is described by a relativistic imperfect fluid. The latter takes into account the dissipative effects (bulk viscosity) arising from…

General Relativity and Quantum Cosmology · Physics 2015-06-23 A. Iorio , G. Lambiase

A plane-symmetric non-static cosmological model representing a bulk viscous fluid distribution has been obtained which is inhomogeneous and anisotropic and a particular case of which is gravitationally radiative. Without assuming any {\it…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Anirudh Pradhan , Hare Ram Pandey

Some properties of cosmological models with a time variable bulk viscous coefficient in presence of adiabatic mater creation and G, c, Lambda variables are investigated in the framework of flat FRW line element. We trivially find a set of…

General Relativity and Quantum Cosmology · Physics 2015-06-25 J. A. Belinchon

In this paper we have investigated an LRS Bianchi I anisotropic cosmological model of the universe by taking time varying $G$ and $\Lambda$ in the presence of bulk viscous fluid source described by full causal non-equilibrium…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Anirudh Pradhan , Purnima Pandey , G. P. Singh , R. V. Deshpandey

We study the late acceleration of the universe by incorporating bulk viscous matter with the running vacuum. The vacuum energy density varies as the squares of the Hubble parameter ($\rho_{\Lambda}\propto H^2$), and the coefficient of bulk…

General Relativity and Quantum Cosmology · Physics 2022-04-27 Sarath N , Jerin Mohan N D , Titus K Mathew

This study investigates the dynamics of a spatially homogeneous and anisotropic LRS Bianchi type-I universe with viscous fluid in the framework of $f(Q)$ symmetric teleparallel gravity. We assume a linear form for $f(Q)$ and introduce…

General Relativity and Quantum Cosmology · Physics 2024-04-16 M. Koussour , S. H. Shekh , M. Bennai , N. Myrzakulov

Bianchi type I magnetized cosmological models in the presence of a bulk viscous fluid are investigated. The source of the magnetic field is due to an electric current produced along x-axis. The distribution consists of an electrically…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Anirudh Pradhan , Om Prakash Pandey

A generally parameterized equation of state (EOS) is investigated in the cosmological evolution with bulk viscosity media modelled as dark fluid, which can be regarded as a unification of dark energy and dark matter. Compared with the case…

Astrophysics · Physics 2009-11-13 J. Ren , Xin He Meng

The Universe is modeled as consisting of pressureless baryonic matter and a bulk viscous fluid which is supposed to represent a unified description of the dark sector. In the homogeneous and isotropic background the \textit{total} energy…

Cosmology and Nongalactic Astrophysics · Physics 2011-11-22 W. Zimdahl , H. E. S. Velten , W. S. Hipólito-Ricaldi

We discuss influences of bulk viscosity on the Early Universe, which is modeled by Friedmann-Robertson-Walker metric and Einstein field equations. We assume that the matter filling the isotropic and homogeneous background is relativistic…

General Relativity and Quantum Cosmology · Physics 2009-12-02 A. Tawfik , H. Mansour , M. Wahba

We analyze the dynamical behavior of a quasi-isotropic Universe in the presence of a cosmological fluid endowed with bulk viscosity. We express the viscosity coefficient as a power-law of the fluid energy density:…

General Relativity and Quantum Cosmology · Physics 2009-03-24 Nakia Carlevaro , Giovanni Montani

Cosmic Microwave Background anomalies suggest that the Universe is slightly anisotropic, so a Cosmological Model that does not satisfy the Cosmological Principle is necessary. Anisotropic Bianchi models have been studied given that they…

General Relativity and Quantum Cosmology · Physics 2017-02-07 Ericsson López , Mario Llerena

The intention of this paper is mainly two-fold. \textit{First}, we point out a striking numerical agreement between the bulk viscosity in the lepton era calculated by Husdal (2016) and our own calculations of the present-day bulk viscosity…

General Relativity and Quantum Cosmology · Physics 2020-07-08 Iver Brevik , Ben David Normann

We study different one-parametric models of type Ia Supernova magnitude evolution on cosmic time scales. Constraints on cosmological and Supernova evolution parameters are obtained by combined fits on the actual data coming from Supernovae,…

Cosmology and Nongalactic Astrophysics · Physics 2010-04-16 Sebastian Linden , Jean-Marc Virey , Andre Tilquin

In this work, we investigate the dynamics of bulk viscous models with decaying vacuum energy density (VED) in a spatially homogeneous and isotropic flat Friedmann-Lema\^{i}tre- Robertson-walker (FLRW) spacetime. We particularly are…

General Relativity and Quantum Cosmology · Physics 2024-01-10 C. P. Singh , Vinita Khatri

A cosmological model with total density close to critical (and flat geometry), dominated by dark matter and dark energy of unknown nature, and consistent with the basic predictions of the inflationary scenario is a very good fit to a…

Astrophysics · Physics 2007-05-23 A. Balbi

Spatially homogeneous and anisotropic Bianchi type V space-time with bulk viscous fluid source and time varying gravitational constant $G$ and cosmological term $\Lambda$ are considered. Coefficient of bulk viscosity $\zeta$ is assumed as a…

General Relativity and Quantum Cosmology · Physics 2012-05-25 Prashant S. Baghel , J. P. Singh

Some cosmological models based on the gravitational theory $f(R) = R+\zeta R^2$, and on fluids obeying to the equations of state of Redlich-Kwong, Berthelot, and Dieterici are proposed for describing smooth transitions between different…

General Relativity and Quantum Cosmology · Physics 2021-10-27 Saikat Chakraborty , Daniele Gregoris

In a recent paper (arXiv:1106.4546), we introduced "dynamical dark matter," a new framework for dark-matter physics, and outlined its underlying theoretical principles and phenomenological possibilities. Unlike most traditional approaches…

High Energy Physics - Phenomenology · Physics 2013-05-30 Keith R. Dienes , Brooks Thomas

The purpose of the present work is two folded: (1) we propose a new mechanism for the origin of bulk viscosity in cosmological context, and then, (2) we address the thermodynamic implications of viscous cosmology based on the thermodynamics…

General Relativity and Quantum Cosmology · Physics 2025-04-02 Tanmoy Paul
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