Viscous cosmology for early- and late-time universe

Brevik, Iver; Grøn, Øyvind; Haro, Jaume de; Odintsov, Sergei D.; Saridakis, Emmanuel N.

doi:10.1142/s0218271817300245

Cited by 206 publications

(149 citation statements)

References 248 publications

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“…As another example of the dark energy models, we may consider the viscous dark energy model (see [51] and the references therein) where a bulk viscosity in the cosmic fluid generates the accelerating expansion of the universe. In the viscous dark energy model, the conservation law of the fluid is modified by the bulk viscosity ζ as follows:…”

Section: Discussionmentioning

confidence: 99%

Covariant generalized holographic dark energy and accelerating universe

2017

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We propose the generalized holographic dark energy model where the infrared cutoff is identified with the combination of the FRW universe parameters: the Hubble rate, particle and future horizons, cosmological constant, the universe lifetime (if finite) and their derivatives. It is demonstrated that with the corresponding choice of the cutoff one can map such holographic dark energy to modified gravity or gravity with a general fluid. Explicitly, F(R) gravity and the general perfect fluid are worked out in detail and the corresponding infrared cutoff is found. Using this correspondence, we get realistic inflation or viable dark energy or a unified inflationary-dark energy universe in terms of covariant holographic dark energy.

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Section: Discussionmentioning

confidence: 99%

Covariant generalized holographic dark energy and accelerating universe

2017

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“…[42][43][44][45][46][47][48][49][50]. Brevik et al [51] discussed the general account about viscous cosmology for early and late time universe. Norman and Brevik [52] analyze characteristic properties of two different viscous cosmology models for the future universe.…”

Section: Introductionmentioning

confidence: 99%

Viscous cosmology in new holographic dark energy model and the cosmic acceleration

Singh

Srivastava

2018

Eur. Phys. J. C

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In this work, we study a flat FriedmannRobertson-Walker universe filled with dark matter and viscous new holographic dark energy. We present four possible solutions of the model depending on the choice of the viscous term. We obtain the evolution of the cosmological quantities such as scale factor, deceleration parameter and transition redshift to observe the effect of viscosity in the evolution. We also emphasis upon the two independent geometrical diagnostics for our model, namely the statefinder and the Om diagnostics. In the first case we study new holographic dark energy model without viscous and obtain power-law expansion of the universe which gives constant deceleration parameter and statefinder parameters. In the limit of the parameter, the model approaches to C DM model. In new holographic dark energy model with viscous, the bulk viscous coefficient is assumed as ζ = ζ 0 + ζ 1 H , where ζ 0 and ζ 1 are constants, and H is the Hubble parameter. In this model, we obtain all possible solutions with viscous term and analyze the expansion history of the universe. We draw the evolution graphs of the scale factor and deceleration parameter. It is observed that the universe transits from deceleration to acceleration for small values of ζ in late time. However, it accelerates very fast from the beginning for large values of ζ . By illustrating the evolutionary trajectories in r −s and r −q planes, we find that our model behaves as an quintessence like for small values of viscous coefficient and a Chaplygin gas like for large values of bulk viscous coefficient at early stage. However, model has close resemblance to that of the C DM cosmology in late time. The Om has positive and negative curvatures for phantom and quintessence models, respectively depending on ζ . Our study shows that the bulk viscosity plays very important role in the expansion history of the universe. a

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“…In recent times, the effect of bulk viscous matter in causing the late acceleration was analysed by many [8][9][10][11][12][13][14]. In a recent review, Brevik et al [15] have shown important implications and capabili-ties of viscosity in describing inflationary era and late time acceleration of the universe; see also Ref. [16].…”

Section: Introductionmentioning

confidence: 99%

Bulk viscous matter and recent acceleration of the universe based on causal viscous theory

2017

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The evolution of the bulk viscous matter dominated universe has been analysed using the full causal theory for the evolution of the viscous pressure in the context of the recent acceleration of the universe. The form of the viscosity is taken as ξ = αρ 1/2 . We obtained analytical solutions for the Hubble parameter and scale factor of the universe. The model parameters have been computed using the observational data. The evolution of the prominent cosmological parameters was obtained. The age of the universe for the best estimated model parameters is found to be less than observational value. The viscous matter behaves like a stiff fluid in the early phase and evolves to a negative pressure fluid in the later phase. The equation of state is found to be stabilised with value ω > −1. The local as well as generalised second law of thermodynamics is satisfied. The statefinder diagnostic shows that this model is distinct from the standard ΛCDM. One of the marked deviations seen in this model to be compared with the corresponding model using the Eckart approach is that in this model the bulk viscosity decreases with the expansion of the universe, while in the Eckart formalism it increases from negative values in the early universe towards positive values.

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Viscous cosmology for early- and late-time universe

Cited by 206 publications

References 248 publications

Covariant generalized holographic dark energy and accelerating universe

Covariant generalized holographic dark energy and accelerating universe

Viscous cosmology in new holographic dark energy model and the cosmic acceleration

Bulk viscous matter and recent acceleration of the universe based on causal viscous theory

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