Barotropic Fluid Distribution Research Articles

Kaluza-Klein Cosmological Models with Barotropic Fluid Distribution

Kaluza-Klein cosmological models have been investigated for barotropic fluid distribution with time dependent gravitational constant and cosmological constant in the context of general relativity. We have used Hybrid Expansion Law (HEL), a product of power-law and exponential type of functions, to obtain determinate solutions of the Einstein’s field equations. In this paper, we have mainly discussed the graphical behavior of the results for three different cases of interest in modern cosmology.

Inflationary scenario in Bianchi Type V space-time for a barotropic fluid distribution with variable bulk viscosity and vacuum energy density

We examine an inflationary scenario in Bianchi Type V space-time for a barotropic fluid distribution with variable bulk viscosity and decaying vacuum energy density. We observe that the matter density ρ, the coefficient of bulk viscosity ζ and the expansion θ all diverge at τ = 0. The spatial volume increases with time, representing an inflationary scenario. The deceleration parameter q 0 corresponding to a decelerated universe. The vacuum energy density Λ decreases with time. The entropy per unit volume is proportional to the absolute temperature. The energy conditions (weak, dominant and strong) are discussed for the model. The reality condition ρ + p ≥ 0 is violated for the inflationary model due to the presence of a scalar field (φ). We also discuss the importance of Bianchi Type V model where the anisotropy dies away during the inflationary era. We also calculate the inflationary parameters and compare the results with the Planck data and discuss their compatibility with anisotropy and BAO estimates. The cosmological constant Λ is a function of time without break general covariance. We also discuss the bounds of the model, how the model isotropizes, where the fluid goes after inflation and how viscosity may realize a graceful exit from inflation to a radiation dominated era.

C-field cosmology for barotropic fluid distribution with variable bulk viscosity and vacuum energy (Λ) in Friedmann–Robertson–Walker (FRW) space–time

A cosmological model that admits barotropic fluid distribution and a negative energy massless scalar creation field as a source in the presence of bulk viscosity and vacuum energy (Λ) in Friedmann–Robertson–Walker space–time is investigated. It has been shown that the model satisfies observational tests and is thus an alternative to the standard Big Bang model. The model is free from real singularity and particle horizon. The creation field increases with time, which matches Hoyle and Narlikar (Proc. Roy. Soc. A, 282, 178 (1964). doi:10.1098/rspa.1964.0225 ). To get the deterministic results, we have assumed that the coefficient of bulk viscosity, ζαρ1/2, where ρ is the matter density, ρ = 3H2, Λ ∼ H2, where H is the Hubble parameter. The model satisfies the energy conditions (weak, dominant, and strong). The deceleration parameter, q < 0, shows that the model represents an accelerating phase of the universe.

LRS Bianchi Type II tilted barotropic fluid cosmological model with heat conduction in general relativity

A tilted cosmological model is studied for a barotropic fluid distribution with heat conduction in the framework of a compact Bianchi Type II space-time. To get a deterministic solution in terms of cosmic time t, we have used the supplementary condition R = S n between the metric potentials R and S, where n is a constant. The shear tensor σ ij for the tilted model satisfies the trace-free condition σ ij v j = 0, where v i is the fluid velocity vector. In a special case, the model becomes non-tilted. The heat conduction vector q i also satisfies the trace-free condition q i v i = 0. The spatial volume increases as time increases, and the model represents an inflationary scenario. The model for a barotropic fluid distribution represents decelerating and accelerating phases of the universe, matching with the astronomical observations. Anisotropy is maintained throughout, but in a special case the model isotropizes. The particle horizon and entropy are discussed. We have also discussed the stiff fluid case with physical and geometrical aspects of the models.

Spatially homogeneous anisotropic Bianchi Type I inflationary universe for barotropic fluid distribution with variable bulk viscosity

Spatially homogeneous anisotropic Bianchi Type I inflationary universe for barotropic fluid distribution with variable bulk viscosity Raj Bali Abstract Spatially homogeneous anisotropic Bianchi Type I inflationary scenario for barotropic fluid distribution with variable bulk viscosity is investigated. To get the deterministic and realistic model, we have assumed Ρ Α 3H2, ζ Α Ρ1/2 as considered by Barrow (1988) and Gron (1990) where Ρ is the matter density, Ρ the bulk viscosity, H the Hubble parameter and conservation equation Tji;j=0 is taken into account. We find that bulk viscosity prevents the matter density to vanish. The model in general represents anisotropic universe but at late time, it isotropizes. The spatial volume increases with time representing inflationary scenario. The energy conditions as given by Kolassis et al. (1998), Chatterjee and Banerjee (2004) are discussed. The energy condition Ρ + p > 0 is violated due to the presence of scalar field (φ) in inflationary universe. Full Text: PDF DOI: 10.15640/ijpa.v3n2a3

C-field cosmological model for barotropic fluid distribution with bulk viscosity and decaying vacuum energy (Λ) in FRW space–time

A solution of Einstein’s field equations that admits barotropic fluid distribution and a negative-energy massless scalar creation field as a source in the presence of bulk viscosity and time-dependent vacuum energy density (Λ) is investigated. It is shown that a cosmological model based on this solution satisfies observational tests and is thus a viable alternative to the standard Big Bang model. The present model is free from real singularity and particle horizon. The creation field increases with time, which matches the result as obtained by Hoyle and Narlikar (Proc. Roy. Soc. A, 282, 178 (1964)). The vacuum energy density, Λ ∼ t–2, matches the result as obtained by Bertolami (Nuovocim. B, 93, 36 (1986)). The spatial volume increases exponentially with time. Thus the model has an inflationary scenario. The deceleration parameter q < 0 indicating that the model represents accelerating expansion of the universe. The presence of the creation field prevents matter density from vanishing and it remains constant for large t. We also observe that bulk viscosity slows down the rate of decrease of volume expansion.

C-Field Cosmological Model for Barotropic Fluid Distribution with Varying Λ in FRW Space Time

A cosmological model for barotropic fluid distribution in creation field cosmology with varying cosmological constant (Λ) in FRW space-time is investigated. To get the deterministic model satisfying conservation equation, we have assumed \(\varLambda = \frac{1}{R^{2}}\) as considered by Chen and Wu (in Phys. Rev. D 41:695, 1990) where R is scale factor. We find that creation field (C) increases with time, which matches with the result of HN Theory (in Hoyle and Narlikar, Proc. R. Astron. Soc. A 282:178, 1964), \(\varLambda\sim\frac{1}{t^{2}}\), the spatial volume increases with time and deceleration parameter q<0 which shows that universe is accelerating. This result matches with recent observations. The inflationary scenario exists in the models and the results so obtained match with astronomical observations. The various special cases of the model (21) viz. dust filled universe (γ=0) and radiation dominated era (ρ=3p), ρ=p (stiff fluid universe) are also discussed. The models are free from horizon.

Bianchi type V viscous fluid cosmological models in presence of decaying vacuum energy

Bianchi type V viscous fluid cosmological model for barotropic fluid distribution with varying cosmological term $\Lambda$ is investigated. We have examined a cosmological scenario proposing a variation law for Hubble parameter $H$ in the background of homogeneous, anisotropic Bianchi type V space-time. The model isotropizes asymptotically and the presence of shear viscosity accelerates the isotropization. The model describes a unified expansion history of the universe indicating initial decelerating expansion and late time accelerating phase. Cosmological consequences of the model are also discussed.

Bianchi type I magnetized cosmological model for barotropoic fluid distribution in Lyra geometry

Bianchi type I cosmological model for barotropic fluid distribution with magnetic field in Lyra geometry is investigated. To get the deterministic solution in terms of comic time t, we have assumed that (eigenvalue of shear tensor ) is proportional to expansion (q). This leads to A = (BC)n, where A, B and C are metric potentials and n is a constant. We also assume that current is flowing along x-axis, therefore, the magnetic field is in yz-plane. The behaviour of the model in the presence and absence of the magnetic field is discussed. We find that the model starts with a big-bang and the expansion in the model decreases as time increases. The displacement vector decreases slowly with time. The model possesses point type and cigar type singularities under different conditions. It has been shown that particle horizon exists in the model. The present investigation is new and is different from other author’s solution. The physical and geometrical aspects of the model in the presence and absence of magnetic field are also discussed. Key words: Bianchi I, magnetized, cosmological, barotropic, Lyra geometry.

Cosmological Models with Variable G in C-Field Cosmology

Cosmological models with variable G in C-field cosmology for barotropic fluid distribution in FRW space-time are investigated. To get the deterministic model of the universe, we have assumed that G=Rn where R is the scale factor and n the constant. To obtain the results in terms of cosmic time t, we have assumed n=−1. We find that for n=−1, Creation field (C) and spatial volume increase with time, G and ρ (matter density) decreases with time, the model represent accelerating universe. Thus inflationary scenario exists in the model. The model is also free from horizon. The results so obtained match with the astronomical observations.

Bianchi Type-III Cosmological Models with Time Dependent Displacement Vector for Barotropic Fluid Distribution in Lyra Geometry

Bianchi Type-III cosmological models for perfect fluid distribution with time dependent displacement field in the framework of Lyra geometry are investigated. To get the deterministic model of the universe, we have assumed two conditions (i) shear (σ) is proportional to the expansion (θ). This leads to B=Cn where B and C are metric potentials and n is a constant. (ii) Universe is filled with barotropic fluid distribution which leads to p=γρ, 0≤γ≤1, p being isotropic pressure and ρ the energy density. The physical and geometrical aspects of the model with a special case and singularities in the models are also discussed.