Temperature variation in the dark cosmic fluid in the late universe

Brevik, Iver

doi:10.1142/s0217732316500504

Cited by 23 publications

(23 citation statements)

References 18 publications

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“…As a (logarithmic) mean of their observations we infer ζ 0 ∼ 10 5 Pa s. The analysis of Sasidharan and Mathew [12] leads to a value for ζ 0 that is somewhat larger, about 7 × 10 7 Pa s. This is roughly in agreement also with Velten and Schwarz [30]. Recent considerations by us led to comparable results [10,13,43]. However, these values are seen to be somewhat large in comparison to our predictions above (cf.…”

Section: Numerical Considerationssupporting

confidence: 89%

Characteristic properties of two different viscous cosmology models for the future universe

Normann

Brevik

2017

Mod. Phys. Lett. A

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We analyze characteristic properties of two different cosmological models: (i) a one-component dark energy model where the bulk viscosity ζ is associated with the fluid as a whole, and (ii) a two-component model where ζ is associated with a dark matter component ρm only, the dark energy component considered inviscid. Shear viscosity is omitted. We assume throughout the simple equation of state p = wρ, with w a constant. In the one-component model we consider two possibilities, either to take ζ proportional to the scalar expansion (equivalent to the Hubble parameter), in which case the evolution becomes critically dependent on the value of the small constant α = 1 + w and the magnitude of ζ. Second, we consider the case ζ = const., where a de Sitter final stage is reached in the future. In the two-component model we consider only the case where the dark matter viscosity ζm is proportional to the square of ρm, where again a de Sitter form is found in the future. In this latter case the formalism is supplemented by a phase space analysis. As a general result of our considerations we suggest that a value ζ0 ∼ 10 6 Pa s for the present viscosity is reasonable, and that the two-component model seems to be favored. 95.36.+x

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Section: Numerical Considerationssupporting

confidence: 89%

Characteristic properties of two different viscous cosmology models for the future universe

Normann

Brevik

2017

Mod. Phys. Lett. A

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“…We mention also the even better agreement with the conservative estimate recently given in Refs. [42] and [6], where the interval 10 4 Pa s < ζ 0 < 10 6 Pa s is found. Also Ref.…”

Section: The Magnitude Of ζmentioning

confidence: 81%

General Bulk-Viscous Solutions and Estimates of Bulk Viscosity in the Cosmic Fluid

Normann

Brevik

2016

Entropy

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Abstract:We derive a general formalism for bulk viscous solutions of the energy-conservation equation for ρ(a, ζ), both for a single-component and a multicomponent fluid in the Friedmann universe. For our purposes, these general solutions become valuable in estimating the order of magnitude of the phenomenological viscosity in the cosmic fluid at present. H(z) observations are found to put an upper limit on the magnitude of the modulus of the present-day bulk viscosity. It is found to be ζ 0 ∼ 10 6 Pa·s, in agreement with previous works. We point out that this magnitude is acceptable from a hydrodynamic point of view. Finally, we bring new insight by using our estimates of ζ to analyze the fate of the future universe. Of special interest is the case ζ ∝ √ ρ for which the fluid, originally situated in the quintessence region, may slide through the phantom barrier and inevitably be driven into a big rip. Typical rip times are found to be a few hundred Gy.Keywords: viscous cosmology; bulk viscosity; big rip; fate of the universe PACS: 98.80.Jk; 95.35.+d; 95.36.+x

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“…Note that the visco-elastic properties of astrophysical media are justifiable under the condition that the astrofluid is strongly coupled (i.e., 1 ≪ Γ < Γ c ). [58] Indeed, the astrophysical media which show the visco-elastic behavior obey such definition and accounted as large-scale cosmic fluids. What is the origin of attractive forces which can cause coagulation of the charged dust particles in different astrophysics media and thus leads to the formation of strongly coupled systems?…”

Section: Discussionmentioning

confidence: 99%

Modified Potential Around a Moving Test Charge in Strongly Coupled Dusty Plasma

Shahmansouri¹,

Farokhi²,

Khodabakhshi³

2017

Commun. Theor. Phys.

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The theory of dynamical (wake) potential behind a moving test charge in a weakly coupled dusty plasma is extended to that including of strong interaction between dust grains. Such strong interaction is included in the dielectric response function by a generalized hydrodynamic (GH) fluid model. It is shown that the strong interaction between dusts including the lattice spacing correction has a significant effect on the wake potential in dusty plasma. This may be used to investigate basic features of phase transition and possibility of lattice formation of dusty plasma.

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Temperature variation in the dark cosmic fluid in the late universe

Cited by 23 publications

References 18 publications

Characteristic properties of two different viscous cosmology models for the future universe

Characteristic properties of two different viscous cosmology models for the future universe

General Bulk-Viscous Solutions and Estimates of Bulk Viscosity in the Cosmic Fluid

Modified Potential Around a Moving Test Charge in Strongly Coupled Dusty Plasma

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