Singularities and soft-Big Bang in a viscous 
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Cruz, Norman; González, Esteban; Jovel, José

doi:10.1103/physrevd.105.024047

Cited by 10 publications

(23 citation statements)

References 96 publications

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“…There are some cosmological models with the attractive quality of avoiding the initial Big-Bang singularity, in which the universe does not have a beginning of time, and therefore, avoids a quantum regime for space-time. For example, a regular scenario called "soft Big-Bang" is discussed in [10][11][12][13][14], describing universes that start in an eternal physical past time that comes from a static universe. Other models correspond to the so-called emergent and bouncing universes [15][16][17][18][19][20][21], with the particularity of avoiding also future singularities like the "Big-Rip" singularities.…”

Section: Introductionmentioning

confidence: 99%

“…To avoid this non-physical issue, a causal theory was proposed by Israel and Stewart (IS) in [50,51], which is capable to reduce to Eckart's theory when the relaxation time for the bulk viscous effects is negligible [52]. Accordingly, Eckart's theory is widely considered in the literature as a first approximation to describe viscous cosmology since the IS theory presents a much greater mathematical difficulty [10,[53][54][55][56][57][58][59]. It is important to mention that, both theories are constructed assuming the so-called near equilibrium condition, which was widely discussed by Maartens in the context of dissipative inflation [52].…”

Section: Introductionmentioning

confidence: 99%

“…As a matter of fact, this viscous pressure Π is proportional to the bulk viscosity coefficient ξ, which depends, particularly, on the temperature and pressure of the viscous fluid [7]. Therefore, a natural election for the bulk viscous coefficient for the dissipative fluid is a dependency proportional to the power of their energy density, an election that has also been explored in the literature in the context of singularities [10,20,22,57,[62][63][64].…”

Section: Introductionmentioning

confidence: 99%

“…The aim of this paper is to study the near equilibrium condition, the mathematical stability, and the positiveness of the entropy production of a non-singular earlytime viscous cosmological model within Eckart's theory in a flat FLRW metric, given by an analytical solution found in [10]. The model itself is dominated by only two fluids: (i) a dissipative radiation component, and (ii) a DE modeled by the CC, which is small but not negligible; and was obtained assuming a bulk viscosity of the form ξ = ξ 0 ρ, where ξ 0 > 0 is the bulk viscous coefficient [7].…”

Section: Introductionmentioning

confidence: 99%

“…The outline of this paper is as follows: In section II we resume the solution found in [10] that represents the model under study. In section III we present general results about the near equilibrium condition, the mathematical stability, and the entropy production.…”

Section: Introductionmentioning

confidence: 99%

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A no-singular early-time viscous cosmological model

Cruz¹,

González²,

Jovel³

2022

Preprint

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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. González, and J. Jovel, Phys. Rev. D 105, 024047 (2022)]. This model represents a flat homogeneous and isotropic universe filled with a dissipative radiation fluid and a cosmological constant Λ, which is small but not negligible, in the framework of Eckart's theory. In particular, we discuss the capability of the solution in the fulfillment of the three following conditions: (i) the near equilibrium condition, which is assumed in Eckart's theory of non-perfect fluids, (ii) the mathematical stability of the solution under small perturbations, and (iii) the positiveness of the entropy production. We have found that this viscous model can describe the radiation domination era of the ΛCDM model and, at the same time, fulfill the three conditions mentioned by the fulfillment of a single constraint on the bulk viscous coefficient ξ0, finding also that this non-singular model has a positive energy density in the infinity past which is infinity hotter with a constant entropy.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A no-singular early-time viscous cosmological model

Cruz¹,

González²,

Jovel³

2022

Preprint

Self Cite

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Finite-time cosmological singularities and the possible fate of the Universe

de Haro,

Nojiri,

Odintsov

et al. 2023

Physics Reports

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Bulk viscous late acceleration under near equilibrium conditions in f(R, T) gravity with mixed dark matter

Pai,

Mathew

2024

Class. Quantum Grav.

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Numerous studies have tried to explain the observed late acceleration of the Universe as being caused by the bulk viscosity associated with the dark matter component. However, for driving the said accelerated expansion, all such models require a violation of Near Equilibrium Conditions (NEC) associated with the background viscous theory. But recently, it was found that, with the aid of a cosmological constant, it is possible to maintain NEC for the bulk viscous warm dark matter during certain evolutionary epochs of the Universe. Nevertheless, this negated the possibility of having a ‘solely’ viscous-driven late acceleration in Einstein gravity within the NEC limit. In the present study, we investigate a model of the universe composed of mixed dark matter components, with viscous dark matter (vDM), and inviscid cold dark matter (CDM) as its constituents, in the context of R + 2λTvm gravity, and show that the model predicts late acceleration by satisfying NEC, critical energy condition (CEC) and second law of thermodynamics (SLT) throughout the evolution, even in the absence of a cosmological constant. One intriguing feature observed in this model is the possibility of having a negative bulk viscous coefficient and yet satisfying the second law of thermodynamics. Finally, by applying both theoretical and observational constraints on the model parameters, we determined the best-fit values of model parameters and thereby analyzed the evolutionary behavior of some relevant cosmological observables.

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Singularities and soft-Big Bang in a viscous ΛCDM model

Cited by 10 publications

References 96 publications

A no-singular early-time viscous cosmological model

A no-singular early-time viscous cosmological model

Finite-time cosmological singularities and the possible fate of the Universe

Bulk viscous late acceleration under near equilibrium conditions in f(R, T) gravity with mixed dark matter

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