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A model of a cloud formed by massive strings is used as a source of Bianchi type II. We assumed that the expansion $(\theta)$ in the model is proportional to the shear $(\sigma)$. To get exact solution, we have considered the equation of…

General Physics · Physics 2015-06-12 Hassan Amirhashchi

We study particle creation in the presence of bulk viscosity of cosmic fluid in the early universe within the framework of open thermodynamical systems. Since the first-order theory of non-equilibrium thermodynamics is non-causal and…

General Relativity and Quantum Cosmology · Physics 2015-04-30 Mehdi Eshaghi , Nematollah Riazi , Ahmad Kiasatpour

In this paper we study the evolution of a LRS Bianchi I Universe, filled with a bulk viscous cosmological fluid in the presence of time varying constants "but" taking into account the effects of a c-variable into the curvature tensor. We…

General Relativity and Quantum Cosmology · Physics 2009-11-10 J. A. Belinchón

We discuss a modified form of gravity implying that the action contains a power \alpha of the scalar curvature. Coupling with the cosmic fluid is assumed. As equation of state for the fluid, we take the simplest version where the pressure…

General Relativity and Quantum Cosmology · Physics 2009-11-11 I. Brevik , O. Gorbunova , Y. A. Shaido

An isotropic expansion for the QGP is proposed in curved Kasner spacetime for an experimental configuration with three dimensional set of beams. The fluid of relativistic particles has no shear viscosity but the nonzero bulk viscosity…

High Energy Physics - Theory · Physics 2012-01-06 Hristu Culetu

The universe media is considered as a non-perfect fluid with bulk viscosity and described by a more general equation of state. We assume the bulk viscosity is a linear combination of the two terms: one is constant, and the other is…

Astrophysics · Physics 2009-03-19 Xin-He Meng , Jie Ren , Ming-Guang Hu

The gravitino problem is revisited in the framework of cosmological models in which the primordial cosmic matter is described by a relativistic imperfect fluid. Dissipative effects (or bulk viscosity effects) arise owing to the different…

Cosmology and Nongalactic Astrophysics · Physics 2017-05-03 L. Buoninfante , G. Lambiase

In this study, we explore the accelerated expansion of the universe within the framework of modified $f(Q)$ gravity. The investigation focus on the role of bulk viscosity in understanding the universe's accelerated expansion. Specifically,…

General Relativity and Quantum Cosmology · Physics 2024-07-09 Dheeraj Singh Rana , P. K. Sahoo

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

Astronomical observations showed that there may exist a bulk flow with peculiar velocities in the universe, which contradicts with the (\Lambda)CDM model. The bulk flow reveals that the observational universe is anisotropic at large scales.…

Cosmology and Nongalactic Astrophysics · Physics 2013-06-07 Zhe Chang , Ming-Hua Li , Sai Wang

A theoretical framework for the calculation of shear and bulk viscosities of hadronic matter at finite temperature is presented. The framework is based on the quasi-particle picture. It allows for an arbitrary number of hadron species with…

Nuclear Theory · Physics 2011-02-01 P. Chakraborty , J. I. Kapusta

We investigate the cosmological implications of a phantom dark energy model with bulk viscosity. We explore this model as a possible way to resolve the big rip singularity problem that plagues the phantom models. We use the latest type Ia…

General Relativity and Quantum Cosmology · Physics 2023-12-21 Jing Yang , Rui-Hui Lin , Chao-Jun Feng , Xiang-Hua Zhai

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

In this work, we have studied how incorporating viscous fluids leads to exact bounce cosmological solutions in general relativity (GR) framework. Specifically, we propose a novel parameterization of bulk viscosity coefficient of the form…

General Relativity and Quantum Cosmology · Physics 2024-07-23 Rajdeep Mazumdar , Mrinnoy M. Gohain , Kalyan Bhuyan

Cylindrically symmetric inhomogeneous cosmological model for bulk viscous fluid distribution with electromagnetic field is obtained. The source of the magnetic field is due to an electric current produced along the z-axis. $F_{12}$ is the…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Anirudh Pradhan , Vandana Rai , Kanti Jotania

We consider a first order formulation of relativistic fluids with bulk viscosity based on a stress-energy tensor introduced by Lichnerowicz. Choosing a barotropic equation of state, we show that this theory satisfies basic physical…

General Relativity and Quantum Cosmology · Physics 2017-10-25 Marcelo M. Disconzi , Thomas W. Kephart , Robert J. Scherrer

Locally-rotationally-symmetric Bianchi type-I viscous and non -viscous cosmological models are explored in general relativity (GR) and in f(R,T) gravity. Solutions are obtained by assuming that the expansion scalar is proportional to the…

General Relativity and Quantum Cosmology · Physics 2021-07-07 S. Jokweni , Vijay Singh , Aroonkumar Beesham

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

The inflationary expansion of our early-time universe is considered in terms of the van der Waals equation, as equation of state for the cosmic fluid, where a bulk viscosity contribution is assumed to be present. The corresponding…

General Relativity and Quantum Cosmology · Physics 2017-12-06 I. Brevik , E. Elizalde , S. D. Odintsov , A. V. Timoshkin

In this paper, we investigate Bianchi type-$VI$ cosmological model for the universe filled with dark energy and viscous fluid in the presence of cosmological constant. Also, we show accelerating expansion of the universe by drawing volume…

General Relativity and Quantum Cosmology · Physics 2013-08-29 J. Sadeghi , Ali R. Amani , N. Tahmasbi