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In this paper, after reconstructing the redshift evolution of the Hubble function by adopting Gaussian process techniques, we estimate the best-fit parameters for some flat Friedmann cosmological models based on a Modified Chaplygin Gas…

Cosmology and Nongalactic Astrophysics · Physics 2021-06-28 Muhsin Aljaf , Daniele Gregoris , Martiros Khurshudyan

Different models of the cosmic substratum which pretend to describe the present stage of accelerated expansion of the Universe like the $\Lambda$CDM model or a Chaplygin gas, can be seen as special realizations of a holographic dark energy…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Winfried Zimdahl

In this paper we make steps in a new direction by considering fluids with EoS of more general form $F(\rho,P)=0$. It is thought that there should be interaction between cosmic fluids, but this assumption for this stage carries only…

General Relativity and Quantum Cosmology · Physics 2014-04-16 J. Sadeghi , M. Khurshudyan , M. Hakobyan , H. Farahani

We consider the cosmological system with two interacting fluids: dark energy and dark matter, in a homogeneous and isotropic universe with dissipation. The modified gravitational equation for dark matter is solved. The analytic…

General Relativity and Quantum Cosmology · Physics 2015-08-19 I. Brevik , V. V. Obukhov , A. V. Timoshkin

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

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

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

To describe dark energy we introduce a fluid model with no free parameter on the microscopic level. The constituents of this fluid are massless particles which are a dynamical realisation of the unextended $D=(3+1)$ Galilei algebra. These…

Cosmology and Nongalactic Astrophysics · Physics 2009-10-29 P. C. Stichel , W. J. Zakrzewski

In this article, we have investigated the role of bulk viscosity to study the accelerated expansion of the universe in the framework of modified $f(Q)$ gravity. The gravitational action in this modified gravity theory has the form $f(Q)$,…

General Relativity and Quantum Cosmology · Physics 2022-07-20 Raja Solanki , S. K. J. Pacif , Abhishek Parida , P. K. Sahoo

We study the evolution of a flat Friedmann-Robertson-Walker Universe, filled with a bulk viscous cosmological fluid, in the presence of time varying ``constants''. The dimensional analysis of the model suggests a proportionality between the…

General Relativity and Quantum Cosmology · Physics 2008-11-26 José Antonio Belinchón , Indrajit Chakrabarty

We consider the dynamics of a causal bulk viscous cosmological fluid filled constantly decelerating Bianchi type I space-time. The matter component of the Universe is assumed to satisfy a linear barotropic equation of state and the state…

General Relativity and Quantum Cosmology · Physics 2008-11-26 M. K. Mak , T. Harko

We present a simple (microscopic) model in which bulk viscosity plays a role in explaining the present acceleration of the universe. The effect of bulk viscosity on the Friedmann equations is to turn the pressure into an "effective"…

Cosmology and Nongalactic Astrophysics · Physics 2011-09-23 Jean-Sebastien Gagnon , Julien Lesgourgues

Currently, a large amount of data implies that the matter constituents of the cosmological dark sector might be collisional. An attractive feature of such a possibility is that, it can reconcile dark matter (DM) and dark energy (DE) in…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-25 K. Kleidis , N. K. Spyrou

In this paper, bulk viscosity is introduced in new holographic dark energy (HDE) to describe the effects of cosmic non-perfect fluid on the evolution of the universe in modified $f(R,T)$ gravity. Assuming $f(R,T)=R+\lambda T$, where $R$ is…

General Relativity and Quantum Cosmology · Physics 2018-04-17 C P Singh , Milan Srivastava

In a spatially flat Friedmann-Lema\^{i}tre-Robertson-Walker universe, we investigate a unified cosmic fluid scenario endowed with bulk viscosity in which the coefficient of the bulk viscosity has a power law evolution. The power law in the…

Cosmology and Nongalactic Astrophysics · Physics 2019-11-20 Weiqiang Yang , Supriya Pan , Eleonora Di Valentino , Andronikos Paliathanasis , Jianbo Lu

We study observational signatures of non-gravitational interactions between the dark components of the cosmic fluid, which can be either due to creation of dark particles from the expanding vacuum or an effect of the clustering of a…

Cosmology and Nongalactic Astrophysics · Physics 2019-12-10 Micol Benetti , Welber Miranda , Humberto A. Borges , Cassio Pigozzo , Saulo Carneiro , Jailson S. Alcaniz

The present work deals with homogeneous and isotropic FLRW model of the Universe having a system of non-interacting diffusive cosmic fluids with barotropic equation of state (constant or variable equation of state parameter). Due to…

General Relativity and Quantum Cosmology · Physics 2019-02-22 Subhayan Maity , Pritikana Bhandari , Subenoy Chakraborty

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

We explore a model of interacting dark energy where the dark energy density is related by the holographic principle to the Hubble parameter, and the decay of the dark energy into matter occurs at a rate comparable to the current value of…

Astrophysics · Physics 2008-12-18 Micheal S. Berger , Hamed Shojaei

We discuss an interacting dark sector model featuring decaying vacuum energy and dark matter empowered by gravitationally induced matter creation. Motivated by quantum field theoretic considerations of vacuum decay and adiabatic particle…

Cosmology and Nongalactic Astrophysics · Physics 2025-09-17 Lokesh Chander , C P Singh
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