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Related papers: A new Parametrization for Bulk Viscosity Cosmology…

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We propose a new model for the viscosity of cosmic matters, which can be applied to different epochs of the universe. Using this model, we include the bulk viscosities as practical corrections to the perfect fluid models of the baryonic and…

General Relativity and Quantum Cosmology · Physics 2022-11-30 Jing Yang , Rui-Hui Lin , Xiang-Hua Zhai

The possibility of dark matter being a dissipative component represents an option for the standard view where cold dark matter (CDM) particles behave on large scales as an ideal fluid. By including a physical mechanism to the dark matter…

Cosmology and Nongalactic Astrophysics · Physics 2015-01-13 Hermano Velten , Thiago R. P. Caramês , Júlio C. Fabris , Luciano Casarini , Ronaldo C. Batista

A generalized dynamical equation for the scale factor of the universe is proposed to describe the cosmological evolution, of which the $\Lambda$CDM model is a special case. It also provides a general example to show the equivalence of the…

Astrophysics · Physics 2009-11-11 J. Ren , X. H. Meng

We consider cosmological scenarios originating from a single imperfect fluid with bulk viscosity and apply Eckart's and both the full and the truncated M\"uller-Israel-Stewart's theories as descriptions of the non-equilibrium processes. Our…

Cosmology and Nongalactic Astrophysics · Physics 2011-09-12 Oliver F. Piattella , Júlio C. Fabris , Winfried Zimdahl

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

We have studied bulk viscosity in the modified $f(Q, T)$ gravity theory formalism, where $Q$ represents the non-metricity and $T$ denotes the trace of energy-momentum tensor within a flat Friedmann-Lema\^{i}tre-Robertson-Walker metric…

General Relativity and Quantum Cosmology · Physics 2021-12-01 Simran Arora , S. K. J. Pacif , Abhishek Parida , P. K. Sahoo

We study the dynamics of a bulk viscosity model in the Eckart approach for a spatially flat Friedmann-Robertson-Walker (FRW) universe. We have included radiation and dark energy, assumed as perfect fluids, and dark matter treated as an…

General Relativity and Quantum Cosmology · Physics 2017-07-07 Yoelsy Leyva , Mirko Sepúlveda

We propose a scenario in which the dark components of the Universe are manifestations of a single bulk viscous fluid. Using dynamical system methods, a qualitative study of the homogeneous, isotropic background scenario is performed in…

Astrophysics · Physics 2008-12-18 R. Colistete , J. C. Fabris , J. Tossa , W. Zimdahl

We utilise a form for the Hubble parameter to generate a number of solutions to the Einstein field equations with variable cosmological constant and variable gravitational constant in the presence of a bulk viscous fluid. The Hubble law…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Anirudh Pradhan , Aotemshi I

Dissipative features of dark matter affect its clustering properties and could lead to observable consequences for the evolution of large--scale structure. We analyse the evolution of cold dark matter density perturbations allowing for the…

Cosmology and Nongalactic Astrophysics · Physics 2019-01-21 Giovanni Acquaviva , Anslyn John , Aurélie Pénin

The renormalization group method is applied to the study of homogeneous and flat Friedmann-Robertson-Walker type Universes, filled with a causal bulk viscous cosmological fluid. The starting point of the study is the consideration of the…

General Relativity and Quantum Cosmology · Physics 2009-09-25 J. A. Belinchon , T. Harko , M. K. Mak

In this article we have presented FRW cosmological model in the framework of Brans-Dicke theory. This paper deals with a new proposed form of deceleration parameter and cosmological constant. The effect of bulk viscosity is also studied in…

General Relativity and Quantum Cosmology · Physics 2017-07-27 G. P. Singh , Binaya K. Bishi

In this paper, we have analyzed the significance of bulk viscosity in an axially symmetric Bianchi type-I model to study the accelerated expansion of the universe. We have considered four bulk viscosity parameterizations for the…

General Relativity and Quantum Cosmology · Physics 2022-12-21 Archana Dixit , Anirudh Pradhan , Vinod Kumar Bhardwaj , A. Beesham

The current paper provides a comprehensive examination of a dark energy cosmological model in the classical regime, in which a generic scalar field is regarded as a dark energy source. Einstein's field equations are solved in model…

General Relativity and Quantum Cosmology · Physics 2022-09-07 Ritika Nagpal , Shibesh Kumar Jas Pacif , Abhishek Parida

The Cold Dark Matter (CDM) model, wherein the dark matter is treated as a pressureless perfect fluid, provides a good fit to galactic and cosmological data. With the advent of precision cosmology, it should be asked whether this simplest…

Cosmology and Nongalactic Astrophysics · Physics 2016-08-12 Michael Kopp , Constantinos Skordis , Dan B. Thomas

The effect of bulk viscisity on the evolution of the homogeneous and isotropic cosmological models is considered. Solutions are found, with a barotropic equation of state, and a viscosity coefficient that is proportional to a power of the…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Pimentel L O , Diaz-Rivera L M

In this study, we construct a theoretical framework based on the generalized Hubble parameter form which may arise within the particle creation, viscous and $f(R)$ gravity theory. The Hubble parameter is scrutinized for its compatibility…

General Relativity and Quantum Cosmology · Physics 2025-03-11 G. P. Singh , Romanshu Garg , Ashutosh Singh

In this paper, we study the thermodynamical and mathematical consistencies for a non-singular early-time viscous cosmological model known as soft-Big Bang, which was previously found in [N. Cruz, E. Gonz\'alez, and J. Jovel, Phys. Rev. D…

General Relativity and Quantum Cosmology · Physics 2023-10-12 Norman Cruz , Esteban González , Jose Jovel

We assume cold dark matter to possess a small bulk-viscous pressure which typically attenuates the growth of inhomogeneities. Explicit calculations, based on Eckart's theory of dissipative processes, reveal that for viscous cold dark matter…

Cosmology and Nongalactic Astrophysics · Physics 2013-11-19 H. Velten , D. J. Schwarz , J. C. Fabris , W. Zimdahl

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