Phase space analysis of bulk viscous matter dominated universe

Sasidharan, Athira; Mathew, Titus K.

doi:10.1007/jhep06(2016)138

Cited by 30 publications

(35 citation statements)

References 82 publications

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“…The effect of bulk viscosity was primarily analysed in the context of acceleration in the early universe, the inflationary epoch [7]. 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.…”

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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Section: Introductionmentioning

confidence: 99%

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

2017

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“…A similar work has been done in reference [39], however, in constraining the parameters (ζ 0 , ζ 1 , ζ 2 ), the authors fixed either ζ 1 or ζ 2 as zero while evaluating the other. In a later work [40] we found that a general evolution of the universe with all the conventional phases (radiation epoch, matter dominated epoch and later acceleration) can be described without any causality violation only when the bulk viscous coefficient is a constant, ζ = ζ 0 .…”

Section: Introductionmentioning

confidence: 88%

“…The coefficient ζ is basically a transport coefficient, hence it would depend on the dynamics of the cosmic fluid. We consider the most general form for the bulk viscous coefficient ζ, which is a linear combination of the three terms [38,39,40,55,56],…”

Section: Bulk Viscous Flrw Universementioning

confidence: 99%

“…In reference [40], we have done the phase space analysis of the model with bulk viscous matter as the dominating cosmic component. Three choices for the bulk viscous coefficient, (i)ζ = ζ 0 + ζ 1ȧ a + ζ 2ä a , (ii)ζ = ζ 0 + ζ 1ȧ a and (iii)ζ = ζ 0 have been adopted.…”

Section: Bulk Viscous Flrw Universementioning

confidence: 99%

“…For the best estimation we have use SCP "Union" 307 SNe Ia data sets. The values of parameter corresponding to the first three cases are extracted in [38,40] Parameters Bulk viscous models ζ = ζ 1ȧ a ζ = ζ 0 + ζ 2ä ã The χ 2 function is constructed as,…”

Section: Bayesian Analysis Of Bulk Viscous Modelsmentioning

confidence: 99%

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Bayesian analysis of bulk viscous matter dominated universe

et al. 2018

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In our previous works, we have analyzed the evolution of bulk viscous matter dominated universe with a more general form for bulk viscous coefficient, ζ = ζ 0 +ζ 1ȧ a +ζ 2ä a and also carried out the dynamical system analysis. We found that the model reasonably describes the evolution of the universe if the viscous coefficient is a constant. In the present work we are contrasting this model with the standard ΛCDM model of the universe using the Bayesian method. We have shown that, even though the viscous model gives a reasonable back ground evolution of the universe, the Bayes factor of the model indicates that, it is not so superior over the ΛCDM model, but have a slight advantage over it.

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Viscous Fluid Cosmology in Symmetric Teleparallel Gravity

Solanki

Rana

Mandal

et al. 2023

Fortschritte der Physik

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In this article, the viscous fluid cosmological model is analyzed in the framework of recently proposed gravity by assuming three different forms of bulk viscosity coefficients, specifically, , , and and a linear model, particularly, where is free model parameter. The bulk viscosity coefficients and the model parameter values using the combined H(z)+Pantheon+BAO data set are estimated. The asymptotic behavior of our cosmological bulk viscous model is studied by utilizing the phase space method. It is found that corresponding to all three cases, our model depicts the evolution of the universe from matter dominated decelerated epoch (a past attractor) to a stable de‐sitter accelerated epoch (a future attractor). Furthermore, the physical behavior of effective pressure, effective equation of state (EoS), and the statefinder parameters are studied. It is also found that the pressure component in the presence of bulk viscosity shows negative behavior and the effective EoS parameter predicts the accelerated expansion phase of the universe for all three cases. Moreover, the trajectories of the model lie in the quintessence region and it converges to the ΛCDM fixed point in the far future. It is found that the accelerated de‐Sitter like phase comes purely from the case without any geometrical modification to GR. Moreover, the late‐time behavior of all three cases of viscosity coefficients are identical. Furthermore, a non‐linear model is considered, specifically, , and then analyzed the behavior of model using dynamical approach. It is also found that the late‐time behavior of the considered non‐linear model with is similar to the linear case, whereas for the case results are quite different.

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Phase space analysis of bulk viscous matter dominated universe

Cited by 30 publications

References 82 publications

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

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

Bayesian analysis of bulk viscous matter dominated universe

Viscous Fluid Cosmology in Symmetric Teleparallel Gravity

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