Cosmological Model In Presence Research Articles

Five Dimensional FRW Radiating Cosmological Model in Presence of Bulk Viscous Fluid in Scalar Tensor Theory of Gravitation

In this paper using the Saez-Ballester scalar-tensor theory of gravitation, we examined a 5-dimensional FRW cosmic space-time in a source of bulk viscous fluid in the article. To examine determinate solutions of the field equations, we used a power law between a scalar field and the universe's scale factor. Our research considers radiating flat, closed, and open models. The physical and kinematical properties of the models were explored in each scenario. In this study, we show that our model expands and is free of initial singularities, as well as that our models decelerate in a conventional manner.
 HIGHLIGHTS
 
 Using the Saez-Ballester theory and a 5-dimensional FRW space-time as a source of bulk viscous fluid, we have obtained cosmological models that can be assumed to be equivalent radiating models in closed, open, and flat space-times
 We have obtained models that are expanding and free of initial singularity
 We used a power law between a scalar field and the universe's scale factor

Microscopic Body Cosmological Model

In this paper we study Bianchi type-I cosmological model in presence of microscopic body in self-creation theory. We solve field equation by using relation B  Am ,C  An and equation of state of microscopic body. Also we discuss physical and kinematical properties and discussed stability of obtained model.

FRW cosmological models in presence of a perfect fluid within the framework of Saez-Ballester theory in five dimensional space time

In the framework of Saez-Ballester scalar-tensor theory of gravity, five-dimensional FRW space-time is considered in the presence of perfect fluid. We employed a power law between the scalar field and the universe's scale factor to get a definite solution to the field equations. Models that radiate flat, closed and open universe are shown. The model's physical features are also discussed.

A comparative study of Kaluza–Klein model with magnetic field in Lyra manifold and general relativity

Kaluza–Klein (K–K) dark energy (DE) cosmological models in presence of magnetized anisotropic fluid have been examined in normal gauge for the field equations for Lyra’s manifold where gauge function β is taken as the function of time. We have chosen the scale factor a(t)=[tkexp(t)]1n (k ≥ 0, n ≥ 0) as the generalized Hybrid expansion law which yields the time-dependent deceleration parameter (DP), to obtain the deterministic solutions of field equations, speaking to a class of models which produce the transition of the universe from the early decelerating stage to the ongoing accelerating stage. The dark energy EoS (ω) is observed to be the time-dependent and its current range for inferred models is in great concurrence with the ongoing observations. For various estimations of (n, k), we can produce a class of physically suitable DE models in K–K theory. The anisotropy of the model vanishes and become isotropic under the suitable condition. The solutions are likewise compared with the solutions in general relativity and without magnetic field. The geometric and physical properties of both the models are likewise talked about in detail.

Anisotropic Cosmological Model in Presence of Holographic Dark Energy and Quintessence

The problem of Bianchi type-III universe filled with matter and holographic dark energy (DE) components is investigated. To obtain a determinant solution, special law of variation for Hubble’s parameter proposed by Berman (Nuovo Cimento B 74: 182, 1983) has been considered. The relationship between holographic dark energy model with the quintessence dark energy has been established. Quintessence potential and dynamics of the quintessence scalar field are reconstructed, which describes the accelerated phase of the expanding universe.

Dynamics of Anisotropic Bianchi Type-III Bulk Viscous String Model with Magnetic Field

In this paper, we discuss the dynamics of spatially homogeneous and anisotropic Bianchi type-III string cosmological model in presence of bulk viscous fluid and electromagnetic field. Exact solutions of Einstein’s field equations are obtained by assuming (i) a special form of the deceleration parameter and (ii) the component \(\sigma^{1}_{1}\) of the shear scalar tensor is proportional to mean Hubble parameter. The source of magnetic field is due to an electric current produced along z-axis. The role of bulk viscosity and magnetic field in establishing string phase of universe is presented. The physical and kinematical features of solutions are also discussed in detail.

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.

Magnetized Domain Walls Cosmological Model in General Relativity

A non-static Bianchi type-III domain walls cosmological models in presence and absence of magnetic field are investigated in general theory of relativity. We assume that F12 is only the non-vanishing component of Fij. To obtain deterministic model, we assume relations B=Cn and ρ=p. Some physical properties of these models are discussed.

Tilted Bianchi Type I dust fluid magnetized cosmological model in general relativity

Tilted Bianchi Type I perfect fluid cosmological model in presence of magnetic field is investigated. To get a determinate solution, we assume p = 0 and A = BC, where A, B and C are metric potentials. A special model is also investigated in the absence of magnetic field. The various physical and geometrical aspects of both the models are also discussed. The effect of the magnetic field on the model is also discussed.

Bianchi Type I Magnetized Barotropic Perfect Fluid Cosmological Model in General Relativity

Bianchi Type I barotropic perfect fluid cosmological model in presence of magnetic field, is investigated. To get the deterministic model, we have also assumed that σ11αθ where σ11 is the eigen-value of shear tensor σij and θ the expansion in the model. The behavior of the model in presence and absence of magnetic field and singularities in the model are also discussed.

A dynamical approach to the cosmological constant

This Letter presents an exact analytic solution of a simple cosmological model in presence of both nonrelativistic matter and scalar field where Einstein's cosmological constant Λ appears as an integration constant. Unlike Einstein's cosmological constant ascribed to vacuum energy, the dark energy density and the energy density of the ordinary matter decrease at the same rate during the expansion of the universe. Therefore the model is free of the coincidence problem. Comparing the predictions using this model with the current cosmological observations shows that the results are consistent.

Bianchi Type I string dust cosmological model with magnetic field in general relativity

Bianchi Type I string dust cosmological models in presence and absence of magnetic field following the techniques used by Letelier and Stachel, are investigated. To get the deterministic solution, we have assumed that σ 1 1 is proportional to the expansion (θ) where σ 1 1 is the eigen value of shear tensor (σ ) and which leads to A=N(BC)−n , n>0 where A,B,C are metric potentials and $n=\frac{\ell +1/3}{\ell -2/3}$ , N and l are constants. The behaviour of the models in presence and absence of magnetic field are discussed. The other physical and geometrical aspects of the model are also discussed.

Cylindrically symmetric inhomogeneous universe with electromagnetic field in string cosmology

Cylindrically symmetric inhomogeneous string cosmological model in presence of electromagnetic field is investigated. We have assumed that F 23 is the only non-vanishing component of F ij . To get the deterministic solution, it has been assumed that the expansion (θ) in the model is proportional to the eigen value σ 1 1 of the shear tensor σ i j . The physical and geometric aspects of the model are also discussed.

Tilted bianchi type v bulk viscous cosmological models in general relativity

Conformally flat tilted Bianchi type V cosmological models in presence of a bulk viscous fluid and heat flow are investigated. The coefficient of bulk viscosity is assumed to be a power function of mass density. Some physical and geometric aspects of the models are also discussed.

Perfect and viscous fluid cosmological models in presence of scalar fields for anisotropic metric

An exact solution of Einstein equations representing a perfect fluid model in the presence of a zero-mass scalar field is obtained for an anisotropic metric. The effect of dissipative processes on the model is also discussed. Different physically valid forms of the scale factors in the three spatial directions give rise to some distinct models. The physical behaviour of these models is discussed in detail. Some of the perfect fluid models exhibit the ‘cigar’ singularity.

Singularity-free RW viscous fluid cosmological models in presence of massive scalar fields

Singularity-free Robertson-Walker cosmological models (RWCM) are developed by considering the cosmic matter as composed of interacting viscous fluid (with zero bulk viscosity) and massive scalar (meson) field. Solutions are obtained for two different cases, viz., when the Hubble's parameterH is epoch independent and whenH is epoch dependent. A solution corresponding to RWCM with only the massive scalar field as the matter content is also presented. Essential physical behaviour of the models developed are discussed in detail.

Singularity-free RW viscous fluid cosmological models in presence of massive scalar fields

Singularity-free RW viscous fluid cosmological models in presence of massive scalar fields

Magneto-viscous fluid cosmological models in presence of zero-mass scalar field

A viscous fluid cosmological model in presence of magnetic field and zero-mass scalar fields is developed. The non-negativity condition of viscous fluid pressure prescribes a certain minimum value oft vis-a-vis of the scale factorQ(t) and at this epoch the model is found to be singularity free.