Bianchi type-V Cosmological Model Research Articles

Locally-rotationally-symmetric Bianchi type-V cosmology in general relativity

A spatially homogeneous locally-rotationally-symmetric (LRS) Bianchi type-V cosmological model is considered with a perfect fluid in general relativity. We present two types of cosmologies (power-law and exponential forms) by using a law of variation for the mean Hubble parameter that yields a constant value for the deceleration parameter. We discuss the physical properties of the non-flat and flat models in each cosmology. Exact solutions that correspond to singular and non-singular models are presented. In a generic situation, models can be interpolated between different phases of the Universe. We find that a constant value for the deceleration parameter is reasonable for a description of different phases of the Universe. We arrive at the conclusion that the Universe decelerates when the value of the deceleration parameter is positive whereas it accelerates when the value is negative. The dynamical behaviours of the solutions and kinematical parameters like expansion, shear and the anisotropy parameter are discussed in detail in each section. Exact expressions for look-back time, luminosity distance and event horizon vs. redshift are derived and their significances are discussed in some detail. It has been observed that the solutions are compatible with the results of recent observations.

Bianchi type-V cosmological models with perfect fluid and heat flow in Saez-Ballester theory

In this paper we discuss the variation law for Hubble’s parameter with average scale factor in a spatially homogeneous and anisotropic Bianchi type-V space-time model, which yields constant value of the deceleration parameter. We derive two laws of variation of the average scale factor with cosmic time, one is of power-law type and the other is of exponential form. Exact solutions of Einstein field equations with perfect fluid and heat conduction are obtained for Bianchi type-V space-time in these two types of cosmologies. In the cosmology with the power-law, the solutions correspond to a cosmological model which starts expanding from the singular state with positive deceleration parameter. In the case of exponential cosmology, we present an accelerating non-singular model of the Universe. We find that the constant value of deceleration parameter is reasonable for the present day Universe and gives an appropriate description of evolution of Universe. We have also discussed different types of physical and kinematical behaviour of the models in these two types of cosmologies.

Bianchi type-V cosmological models with perfect fluid and dark energy

We consider a self-consistent system of Bianchi type-V cosmology and binary mixture of perfect fluid and dark energy. The perfect fluid is taken to be one obeying the usual equation of state p=γρ with γ∈[0,1]. The dark energy is considered to be either the quintessence or Chaplygin gas. Exact solutions to the corresponding Einstein equations are obtained as a quadrature. The cases of disordered radiation and models with power-law and exponential expansion have discussed in detail. For large t, the models tend to be isotropic.

Bianchi type-V anisotropic cosmological models in certain theories of gravitation with perfect fluid distribution

Exact Bianchi type-V cosmological models are presented in Einstein’s theory of gravitation with cosmological constant Λ in case of perfect fluid distribution. Also obtained Bianchi type-V cosmological models in a scalar-tensor theory of gravitation proposed by Saez and Ballester (1986) in case of perfect fluid distribution using and without using negative constant deceleration parameter. Some physical and geometrical properties of the models are also discussed.

Exact Bianchi type-V perfect fluid cosmological models in Brans–Dicke theory of gravitation

Exact Bianchi type-V cosmological models are obtained in a scalar-tensor theory of gravitation proposed by Brans and Dicke (Phys. Rev. 124:925, 1961) in the presence of perfect fluid distribution. Some physical and geometrical properties of the models are also discussed.

An exact Bianchi type-V cosmological model in Saez-Ballester theory of gravitation

An exact Bianchi type-V cosmological model is obtained in a scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986) in case of perfect fluid distribution. Some physical properties of the model are also discussed.

Some cosmological models with heat and null radiation flow

Some New Bianchi type-V cosmological models, incorporating heat flow and null radiation flow, along with perfect fluid distribution have been discussed. The physical and kinematical behaviors of the models have been analyzed.

Bianchi Type-V universe with a viscous fluid and Λ-term

We have studied the evolution of a homogeneous, anisotropic universe given by a Bianchi Type-V cosmological model filled with viscous fluid, in the presence of cos- mological constant Λ. The role of viscous fluid and Λ-term in the Bianchi Type-V universe has been studied.

Conformally flat tilted Bianchi Type-V cosmological models in general relativity

We have investigated two conformally flat tilted Bianchi Type-V cosmological models in general relativity. To get a determinate solution, we have assumed a supplementary conditionA =B n between metric potentials wheren is a constant. The behaviour of the model forn = 2 is discussed in detail. Various physical and geometrical aspects of the models are also discussed.

A Bianchi type-V cosmological model with spin matter

Analytic solutions of a particular anisotropic Bianchi type-V cosmological model with spin matter have been found. In the radiation epoch, when the spin energy is larger than the anisotropic energy (i.e. ), the initial singularity can be avoided. We have incorporated the Guth inflationary Universe model into the Einstein - Cartan theory of gravitation which is useful for studying cosmological models with some kind of anisotropy. The inflationary solutions depend on the value of . When , the Universe does not have an inflationary phase. The implications of these solutions will be discussed in the text. This anisotropic model can also evolve to an isotropic one.

Dynamical systems approach to tilted Bianchi cosmologies: Irrotational models of type V.

We write the Einstein field equations for the irrotational tilted Bianchi type-V cosmological models as an autonomous differential equation in terms of expansion-normalized dimensionless variables. The theory of dynamical systems is then used to give a complete qualitative description of the evolution of the models with nonextreme tilt.

Minisuperspace example of non-Lagrangian quantization.

We present the construction of a Hamiltonian description for a (non-Lagrangian) Bianchi type-V cosmological model using the solutions of the equations of motion as a starting point. We study the quantization of the model and compare our results to those found using a more standard approach.

Vacuum bianchi type-V cosmological models in Ross and Dunn scalar-tensor theories of gravitation

It is shown that the relativistic analogues of vacuum Bianchi type-V cosmological models, in the scalar-tensor theories of gravitation proposed by Ross and Dunn, do not exist.

Numerical nucleosynthesis results for Bianchi type-V cosmological models

Results of numerical calculations of helium-4 and deuterium abundances in a wide range of Bianchi type-V locally rotationally-symmetric cosmological models are presented. The tabulated element abundances show that these models generically yield helium fractions which are unacceptably large compared with the available observational data.

Tilted Bianchi type-V cosmological model in the scale-covariant theory

We derive tilted Bianchi type-V cosmological models in the scale-covariant theory. The solution for radiation is discussed separately from that for the non-radiative case.

Study of a Bianchi type-V cosmological model with torsion

A Bianchi type-V exact solution of the Einstein-Cartan theory representing several classes of perfect-fluid homogeneous cosmological models is studied. With the introduction of an effective energy-momentum tensor, a dual description of the solution is given within the framework of general relativity, whereby it is shown that the two theories, although formally equivalent, provide physically inequivalent interpretations of the solution. Examined in some detail are the singularity behavior as well as other features of the models.