Wavefront speeds in power-law inflation driven by bulk viscosity and matter creation

1997 ◽  
Vol 14 (5) ◽  
pp. 1387-1391 ◽  
Author(s):  
J Gariel ◽  
G Le Denmat ◽  
N O Santos
Keyword(s):  
Power Law ◽  
Bulk Viscosity ◽  
Matter Creation

scholarly journals STUDY OF THE QUASI-ISOTROPIC SOLUTION NEAR THE COSMOLOGICAL SINGULARITY IN THE PRESENCE OF BULK VISCOSITY

2008 ◽  
Vol 17 (06) ◽  
pp. 881-896 ◽  
Author(s):  
NAKIA CARLEVARO ◽  
GIOVANNI MONTANI
Keyword(s):  
Power Law ◽  
Bulk Viscosity ◽  
Dynamical Behavior ◽  
Viscosity Coefficient ◽  
Viscous Effects ◽  
Isotropic Universe ◽  
Cosmological Singularity ◽  
Isotropic Solution ◽  
Second Order In Time ◽  
The Universe

We analyze the dynamical behavior of a quasi-isotropic universe in the presence of a cosmological fluid endowed with bulk viscosity. We express the viscosity coefficient as a power law of the fluid energy density: ζ = ζ0∊s. Then we fix s = 1/2 as the only case in which viscosity plays a significant role in the singularity physics but does not dominate the universe dynamics (as required by its microscopic perturbative origin). The parameter ζ0is left free to define the intensity of the viscous effects.In spirit of the work by Lifshitz and Khalatnikov on the quasi-isotropic solution, we analyze both Einstein and hydrodynamic equations up to first and second order in time. As a result, we get a power law solution existing only in correspondence to a restricted domain of ζ0.

HIGHER DIMENSIONAL COSMOLOGICAL MODEL IN LYRA GEOMETRY: REVISITED

2003 ◽  
Vol 12 (05) ◽  
pp. 853-860 ◽  
Author(s):  
G. P. SINGH ◽  
S. KOTAMBKAR ◽  
ANIRUDH PRADHAN
Keyword(s):  
Cosmological Model ◽  
Power Law ◽  
Bulk Viscosity ◽  
Research Work ◽  
Lyra Geometry ◽  
Universe Model ◽  
Higher Dimensional ◽  
Empty Universe ◽  
Kaluza Klein

In this paper we have revisited the research work of Rahman and Bera22on Kaluza–Klein cosmological model within the framework of Lyra Geometry. It has been shown that the empty universe model yields a power law relation without any assumption. The role of bulk viscosity on five-dimensional cosmological model is discussed. The physical behaviour of the models is examined in all cases.

scholarly journals ON THE ROLE OF VISCOSITY IN EARLY COSMOLOGY

2008 ◽  
Vol 23 (08) ◽  
pp. 1248-1252
Author(s):  
NAKIA CARLEVARO ◽  
GIOVANNI MONTANI
Keyword(s):  
Energy Density ◽  
Power Law ◽  
Bulk Viscosity ◽  
Viscosity Coefficient ◽  
Hydrodynamic Equations ◽  
Restricted Domain ◽  
Asymptotic Approach ◽  
Cosmological Singularity ◽  
Second Order In Time

We present a discussion of the effects induced by bulk viscosity on the very early Universe stability. The viscosity coefficient is assumed to be related to the energy density ρ via a power-law of the form ζ = ζ0ρs (where ζ0, s = const.) and the behavior of the density contrast in analyzed. In particular, we study both Einstein and hydrodynamic equations up to first and second order in time in the so-called quasi-isotropic collapsing picture near the cosmological singularity. As a result, we get a power-law solution existing only in correspondence to a restricted domain of ζ0. The particular case of pure isotropic FRW dynamics is then analyzed and we show how the asymptotic approach to the initial singularity admits an unstable collapsing picture.

Dark energy and viscous cosmology with variable G and Λ in an anisotropic background

2013 ◽  
Vol 91 (2) ◽  
pp. 153-157 ◽  
Author(s):  
V. Fayaz ◽  
M.R. Setare ◽  
H. Hossienkhani
Keyword(s):  
Dark Energy ◽  
Power Law ◽  
Bulk Viscosity ◽  
Deceleration Parameter ◽  
Chaplygin Gas ◽  
Density Parameter ◽  
Type I ◽  
De Sitter ◽  
Variable G And Λ ◽  
Variable G

The general Bianchi type I with dark energy in the form of standard and modified Chaplygin gas with variable G and Λ and bulk viscosity have been investigated. The de Sitter, power-law and general exponential solutions are assumed for the scale factor in each spatial direction and the corresponding cosmological models are reconstructed. Moreover, for the general exponential solutions, from which the de Sitter and power-law solutions may be obtained, we obtain models that reproduce the early universe, assumed as the inflation, and the late time accelerated expanding universe, that which yields a constant value for the deceleration parameter. We reconstruct bulk viscosity, ξ, gravitational parameter, G, cosmological term, Λ, density parameter, Ω, cosmological constant density parameter, ΩΛ, and deceleration parameter, q, for different equations of state. In the large time limit the model describes an accelerating universe wherein the effective negative pressure induced by Chaplygin gas and bulk viscous pressure are driving the acceleration.

On the equivalence of bulk viscosity and matter creation

1992 ◽  
Vol 170 (5) ◽  
pp. 373-378 ◽  
Author(s):  
J.A.S. Lima ◽  
A.S.M. Germano
Keyword(s):  
Bulk Viscosity ◽  
Matter Creation

scholarly journals Stability Analysis of Bulk Viscous Cosmology

2018 ◽  
Vol 168 ◽  
pp. 08006 ◽  
Author(s):  
M. Sharif ◽  
Saadia Mumtaz
Keyword(s):  
Power Law ◽  
Bulk Viscosity ◽  
Viscosity Coefficient ◽  
Study Phase ◽  
Universe Model ◽  
Power Law Model ◽  
Frw Universe ◽  
Dimensionless Variables ◽  
The Stability ◽  
Bulk Viscosity Coefficient

In this paper, we study phase space analysis of FRW universe model by taking a power-law model for bulk viscosity coefficient. An autonomous system of equations is developed by defining normalized dimensionless variables. We find corresponding critical points for di.erent values of the parameters to investigate stability of the system. It is found that the presence of power-law model of bulk viscosity appears as an e.ective ingredient to enhance the stability of the respective universe model.

Critical region ultrasonsic attenuation in the condensed inert gases

1983 ◽  
Vol 61 (6) ◽  
pp. 895-902 ◽  
Author(s):  
J. A. Cowan ◽  
J. W. Leech
Keyword(s):  
Power Law ◽  
Bulk Viscosity ◽  
Vapour Pressure ◽  
Critical Region ◽  
High Frequency ◽  
Inert Gases ◽  
Saturated Vapour Pressure ◽  
Critical Isochore ◽  
Saturated Vapour ◽  
Inverse Power Law

New measurements in the range 5–15 MHz are reported for Kr and Xe along the saturated vapour pressure (SVP) line and the critical isochore. Analyzed together with previous 55 Mz measurements the results indicate a limiting high frequency corresponding states behaviour in which both the attenuation and those parts of the measurements associated with bulk viscosity and critical point effects show simple inverse power law dependence on [Formula: see text].

scholarly journals Cosmic expansion with matter creation and bulk viscosity

2020 ◽  
Vol 102 (12) ◽  
Author(s):  
Víctor H. Cárdenas ◽  
Miguel Cruz ◽  
Samuel Lepe
Keyword(s):  
Bulk Viscosity ◽  
Cosmic Expansion ◽  
Matter Creation
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