Exact analytical solution for an Israel–Stewart cosmology

Cruz, Norman; González, Esteban; Palma, G.

doi:10.1007/s10714-020-02712-z

Cited by 20 publications

(20 citation statements)

References 28 publications

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“…Since no other fluid was included in order to obtain this solution, it is suitable only to describe the late times evolution. Furthermore, according to [27] the accelerated expansion can be described within a range of the parameters of the model for a pressureless DM fluid, which are compatible with OHD and SNe Ia data. The main motivation to include the non linear extension of the Israel-Stewart theory comes from the fact that the aforementioned exact solution represents an accelerated universe, which means that the near equilibrium condition is violated, i.e., the viscous stress is greater than the equilibrium pressure p. The description of relativistic non-perfect fluids within the causal and non-causal approaches require the validity of the near equilibrium regime.…”

Section: Introductionsupporting

confidence: 62%

“…Our aim in this paper is to study the capability to fit the SNe Ia data by an exact solution found in the non linear regime of the Israel-Stewart theory and compare it with the ΛCDM model. Such solution represents a generalization of one found previously in the context of linear regime for an unified model of dissipative dark matter (DM) [27]. Since no other fluid was included in order to obtain this solution, it is suitable only to describe the late times evolution.…”

Section: Introductionmentioning

confidence: 80%

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Testing a non linear solution of the Israel-Stewart theory with supernovae

Crúz¹,

Cruz²,

González³

et al. 2021

Preprint

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In this work we test the capability of an exact solution found in the framework of a non linear extension of the Israel-Stewart theory to fit the supernovae Ia data. This exact solution is a generalization of one previously found in the context of the near equilibrium description of dissipative processes, where a dissipative unified dark matter model is studied, considering that such generalized solution does not represent the full regime of the non linear picture. We restrict the solution to the case where a positive entropy production is guaranteed. It is found that for some specific values of the parameter that characterizes the non linear effects, namely k, the model fits the supernovae Ia data slightly better than the ΛCDM model.

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Section: Introductionsupporting

confidence: 62%

Section: Introductionmentioning

confidence: 80%

Testing a non linear solution of the Israel-Stewart theory with supernovae

Crúz¹,

Cruz²,

González³

et al. 2021

Preprint

Self Cite

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show abstract

“…The main difference between them is that the Eckart formalism is a non causal theory and, as a consequence, it is simpler than the IS. Indeed, only one bulk viscosity model of the form ξ ∼ ρ s (where ρ is the energy density considered typically as dust matter) has been studied [36][37][38][39][40] in the IS theory, while several models have been explored [41][42][43][44][45][46][47][48] in the Eckart one.…”

Section: Introductionmentioning

confidence: 99%

A hybrid model of viscous and Chaplygin gas to tackle the Universe acceleration

et al. 2021

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Motivated by two seminal models proposed to explain the Universe acceleration, this paper is devoted to study a hybrid model which is constructed through a generalized Chaplygin gas with the addition of a bulk viscosity. We call the model a viscous generalized Chaplygin gas (VGCG) and its free parameters are constrained through several cosmological data like the Observational Hubble Parameter, Type Ia Supernovae, Baryon Acoustic Oscillations, Strong Lensing Systems, HII Galaxies and using Joint Bayesian analysis. In addition, we implement a Om-diagnostic to analyze the VGCC dynamics and its difference with the standard cosmological model. The hybrid model shows important differences when compared with the standard cosmological model. Finally, based on our Joint analysis we find that the VGCG could be an interesting candidate to alleviate the well-known Hubble constant tension.

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“…The latter is characterized by first-order gradients of the hydrodynamical variable, i.e., the dissipative quantities are constructed from the first-order gradients of the fluid's four-velocity, temperature, and chemical potential. But it was ascertained that the dissipative perturbation has infinite speed [11][12][13][14]. A linear relation between the bulk viscous pressure and the expansion in the early Universe was also suggested [5].…”

Section: Introductionmentioning

confidence: 99%

“…When repairing this in light of the theory of general relativity, Mueller [16] and Israel-Stewart [17,18] came up with a causal theory which is stable under linear perturbations and the dissipative perturbation has finite speed [15]. Here, the second-order gradients are dominant [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Cosmic Evolution of Viscous QCD Epoch in Causal Eckart Frame

Hakk

Tawfik²,

Nada

et al. 2021

Universe

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It is conjectured that in cosmological applications the particle current is not modified but finite heat or energy flow. Therefore, comoving Eckart frame is a suitable choice, as it merely ceases the charge and particle diffusion and conserves charges and particles. The cosmic evolution of viscous hadron and parton epochs in casual and non-casual Eckart frame is analyzed. By proposing equations of state deduced from recent lattice QCD simulations including pressure p, energy density ρ, and temperature T, the Friedmann equations are solved. We introduce expressions for the temporal evolution of the Hubble parameter H˙, the cosmic energy density ρ˙, and the share η˙ and the bulk viscous coefficient ζ˙. We also suggest how the bulk viscous pressure Π could be related to H. We conclude that the relativistic theory of fluids, the Eckart frame, and the finite viscous coefficients play essential roles in the cosmic evolution, especially in the hadron and parton epochs.

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Exact analytical solution for an Israel–Stewart cosmology

Cited by 20 publications

References 28 publications

Testing a non linear solution of the Israel-Stewart theory with supernovae

Testing a non linear solution of the Israel-Stewart theory with supernovae

A hybrid model of viscous and Chaplygin gas to tackle the Universe acceleration

Cosmic Evolution of Viscous QCD Epoch in Causal Eckart Frame

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