Bianchi type-V bulk viscous cosmological models with particle creation in Brans-Dicke theory

The Bianchi type-V cosmological model with viscous fluid and creation particle in Brans-Dicke theory has been considered. The present paper deals with Bianchi type-V cosmological model with bulk viscosity and particle creation described by full causal thermodynamics in Brans-Dicke theory. We have discussed two types of solutions of the average scale factor for a Bianchi type-V model by using a variation law of Hubble’s parameter, which yields a constant value of the deceleration parameter. The exact solutions to the corresponding field equations are obtained in quadrature form. The solutions to the Einstein field equations are obtained for power law and exponential form. The cosmological parameters have been discussed in detail.     

The general class of Bianchi cosmological models with viscous fluid and particle creation in Brans-Dicke theory

This paper deals with the general class of Bianchi cosmological models with bulk viscosity and particle creation described by full causal thermodynamics in Brans-Dicke theory. We discuss three types of average scale-factor solutions for the general class of Bianchi cosmological models by using a special law for the deceler- ation parameter which is linear in time with a negative slope. The exact solutions to the corresponding field equations are obtained in quadrature form and solutions to the Einstein field equations are obtained for three different physically viable cosmologies. All the physical parameters are calculated and discussed in each model.     

Cosmological solution in Brans-Dicke theory involving particle creation

By considering the Robertson-Walker line element exact cosmological solutions have been obtained by taking spin-half-generated particles as matter sources in the Jordan-Brans-Dicke theory. There exist exact solutions for which the gravitational constant decreases linearly with time and the mass of the Universe increases proportionally to the square of its age while the density decreases with time. The results have been studied corresponding to the three values of curvature index. It has been shown that the expansion law is determined by the particles created by the expansion itself.     

Qualitative analysis of cosmological models in Brans-Dicke theory

Isotropic and homogeneous cosmological models with a perfect fluid cource in Brans-Dicke theory are investigated from the point of view of dynamical system theory.Work partially supported by CNPq (Brazil).     

Anisotropic bulk viscous cosmological models with particle creation

This paper is devoted to the study of role of particle creation and bulk viscosity on evolution of homogeneous and anisotropic model of the universe represented by Bianchi type I space time metric. Particle creation and bulk viscosity have been considered as separated irreversible processes. In order to discuss physical and geometrical behaviour of the model, a new set of exact solutions of Einstein’s field equation have been obtained in non-causal, truncated and full causal theories. Dynamical behaviours of models have also been discussed.     

Axially symmetric string cosmological models in Brans-Dicke theory of gravitation

Axially symmetric string cosmological models are obtained in a scalar- tensor theory of gravitation proposed by Brans and Dicke (Phys. Rev. 124:925, 1961). Some physical and geometrical properties of the models are also discussed. The models are anisotropic and free from singularities.     

The cosmological model of Brans-Dicke theory

We use the generalized Brans-Dicke theory, in which the Pauli metric is identified to be the physical space-time metric, to study the Universe in different epochs. Exact analytical expressions for dilaton field , cosmological radiusR and density parameter are obtained fork=+1,0,–1 Universe in the radiation-dominated epoch. For matter dominated Epoch, exact analytical expressions for Hubble parameterH, cosmological radius, dilaton field, deceleration factorq, density parameter and the gravitational coupling of the ordinary matter are obtained for the flat Universe. Other important results are: (1) the density parameter is always less than unity for the flat Universe because the dilaton field plays a role as an effective dark matter, and (2) the new Brans-Dicke parameter must be larger than 31.75 in order to consistent with the observed data.     

A class of cosmological solutions of Brans-Dicke theory with cosmological constant

We present a class of exact cosmological solutions of Brans-Dicke (B-D) equations with cosmological constant in flat Robertson-Walker metric. These solutions are based on the relation øR ⁿ= constant between the B-D field and the scale factor of the universe. This relation turns out to be consistent with the equation of statep =m for the cosmic matter, provided thatn andm are suitably related to each other. Several special cases and asymptotic solutions are derived and discussed.     

An anisotropic cosmological model in Brans-Dicke theory

Solutions of Brans-Dicke field equations are obtained when the source of the gravitational field is a perfect fluid with pressure equal to energy density and the metric is cylindrically symmetric of Marder-type. Various physical and geometrical properties of the model have been discussed. Finally the solutions have been transformed to the original form of Brans-Dicke (1961) theory and then through unit transformation to a general form.     

Exact Bianchi type-I cosmological model with matter in Brans-Dicke theory

In this paper an exact solution of the Brans-Dicke field equations in the presence of stiff matter is obtained for the Bianchi type-I cosmological space-time. The new solution represents an anisotropic homogeneous cosmological model which tends to anisotropic expansion. The behaviour of the solution near the singularities and late stages of the expansion is discussed.     

Slowly rotating cosmological perfect fluids in Brans-Dicke theory

The Brans-Dicke field equations for a perfect fluid distribution representing slowly rotating fluid spheres are investigated. Exact solutions are obtained for differential rotation and perfect dragging by imposing some physical restrictions on the matter rotation (r,t). The physical properties are discussed fork=±1.     

Plane symmetric cosmological models with negative constant deceleration parameter in self creation theory

In this paper, we have investigated plane symmetric cosmological models with negative constant deceleration parameter in Barber’s (Gen. Relativ. Gravit. 14:117, 1982) second self-creation theory in presence of perfect fluid source. For this we use a special law of variation for Hubble parameter proposed by Bermann (Nuovo Cim. B 74:182, 1983) that yields a constant deceleration parameter model of the universe. Some physical properties of the models and entropy are discussed and studied.     

Slowly rotating cosmological viscous fluid universe in Brans-Dicke theory

The Brans-Dicke field equations for a viscous distribution representing slowly rotating fluid spheres are investigated. Exact solutions are obtained for differential rotation by imposing physical restrictions on the matter rotation (r,t). The physical properties are discussed fork=±1.     

Friedmann cosmology with a cosmological constant in the modified Brans-Dicke theory

Homogenous isotropic cosmologies in the presence of a cosmological constant A are studied in the modified Brans-Dicke theory. A class of exact solutions are obtained in Dicke's revised units for empty space as well as for the models filled with dust or radiation. Behaviour of these models near the singularity are discussed.     

A String cosmological model in Brans-Dicke theory of gravitation

A spatially homogeneous and anisotropic exact Bianchi type-I string cosmological model is investigated in Brans-Dicke (1961) scalar-tensor theory of gravitation. Some properties of the model are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Exact Bianchi type-VI0 vacuum cosmological model in Brans-Dicke theory

We present an exact solution of the vacuum Brans-Dicke field equations for cosmological models of Bianchi type-VI₀. The solution represents anisotropic universe which has no analogy in Einstein's theory.     

Exact Bianchi type VI0 cosmological solutions with matter in Brans-Dicke theory

We present an exact solution of the Brans-Dicke equations for cosmological models of Bianchi type VI₀ with stiff matter. The solution represents anisotropic universe which has its analogy in Einstein's theory. The corresponding result for a plane symmetry Bianchi type I model is obtained as a special case.