Cosmological Scalar in the Jordan-Brans-Dicke Theory. I

A variant of the Jordan-Brans-Dicke (JBD) theory is examined which contains a cosmological scalar that is written so that on going to the Einstein representation it becomes the ordinary cosmological constant of general relativity theory. This paper is divided into two parts. In Part I we examine the cosmological solutions for the Einstein representation of the JBD theory, i.e., in the presence of a minimally coupled scalar field. In Part II we shall study the cosmological solutions in the proper representation of the JBD theory with a self consistent scalar field. The analysis of these solutions is of interest in connection with modern concepts of the evolution of the universe, in particular, with the observed acceleration of cosmological expansion and estimates of the density of dark matter and dark energy.__________Translated from Astrofizika, Vol. 48, No. 3, pp. 455–462 (August 2005).     

关于有挠时空理论中的宇宙模型

本文阐明了引力规范理论的自治性.以简单的R+Q~2理论为例讨论了宇宙模型.挠率的存在并不改变标准宇宙模型的结果.     

Some results in the general scalar tensor theory

Raychaudhuri-type equations are written for a cosmological model filled with a perfect fluid and obeying the equations of general scalar-tensor theory proposed by Nordtvedt. It is found that a non-rotating cosmological model may, in general, have a minimum volume. The Hawking-Penrose energy condition suggests that the singularity can be avoided in this theory.     

Relativistic non-zero pressure cosmology

A further extension of the theory of interacting matter-radiation cosmological models is presented. The neutrino contribution to the radiation field is explicitly included. A discussion and interpretation of the observables within the theory is given. Mean evolutionary corrections for galaxies are shown to be implied by these models. Finally, as an example we present a cosmological interpretation of quasars.     

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.     

Bianchi type-III cosmological model in four- and five-dimensional bimetric theory of relativity

Four- and five-dimensional Bianchi type-III cosmological model in Rosen (1980) bimetric theory of gravitation is considered. Restricting to a particular type of background metric, it is observed that the Bianchi type-III cosmological model does not exist in case of both meson field and mesonic perfect fluid. Hence only vacuum model can be obtained.     

Modified equations in the theory of induced gravity. Solution to the cosmological constant problem

This research is an extension of the author’s works, in which conformally invariant generalization of string theory was suggested to higher-dimensional objects. Special cases of the proposed theory are Einstein’s theory of gravity and string theory. This work is devoted to the formation of self-consistent equations of the theory of induced gravity in the presence of matter in the form of a perfect fluid that interacts with scalar fields. The study is done to solve these equations for the case of the cosmological model. In this model time-evolving gravitational and cosmological “constants” take place which are determined by the square of scalar fields. The values of which can be matched with the observational data. The equations that describe the theory have solutions that can both match with the solutions of the standard theory of gravity as well as it can differ from it. This is due to the fact that the fundamental “constants” of the theory, such as gravitational and cosmological, can evolve over time and also depend of the coordinates. Thus, in a rather general case the theory describes the two systems (stages): Einstein and “evolving”. This process is similar to the phenomenon of phase transition, where the different phases (Einstein gravity system, but with different constants) transit into each other.     

Some general results in self-creation cosmologies

Raychaudhuri-type equations are written for a cosmological model filled with perfect fluid and obeying the equations of a self-creation theory recently proposed by G. A. Barber. In addition some general results on spatially homogeneous cosmological models are obtained. The Hawking-Penrose energy condition suggests that the singularity can be avoided in this theory.     

The Cosmological Scalar in the Jordan-Brans-Dicke Theory. II.

Cosmological solutions are examined in the proper representation of the JBD theory with a dominant nonminimally coupled scalar field. It is shown that only the introduction of a cosmological scalar that transforms to the ordinary cosmological constant in the Einstein representation enables a phase of evolution with a uniform and then an accelerated expansion of the universe over cosmological time scales. __________ Translated from Astrofizika, Vol. 48, No. 4, pp. 633–640 (November 2005).     

Ages of the universe for FRW-type models in wesson's 5D variable mass theory of gravity

The age of the universe is computed for spatially homogeneous and isotropic cosmological models of the relativistic Wesson's 5D variable mass theory of gravity. It is shown that if the pressure in the mass dimension is negligible, ages old enough to agree with the observations can only be obtained if the cosmological constant is different from zero. In addition, unlike the standard FRW models in Einstein's 4D theory, the age value itself is not affected by the nature of the matter content (matter and radiation dominated models give the same age).     

Non-vacuum cosmological solutions of 5D variable mass theory of gravity

A class of non-vacuum expanding cosmological solutions of Wesson's 5D theory of gravity with variable rest mass is derived. The models are spatially homogeneous and isotropic and the source of gravitation is a pressureless fluid (dust) plus a cosmological constant term. The general and unified solution is found for the equations and some properties of different limiting cases are studied. Particularly, it is shown that for null cosmological constant the predicted age of the universe is smaller than the ones of the 4D FRW models.     

Bianchi type-I string cosmological models in bimetric theory of gravitation

Bianchi type-I string cosmological models are obtained in bimetric theory of gravitation proposed by Rosen (Gen. Relativ. Gravit. 4:435, 1973). Established the existence of string cosmological models, unlike the earlier authors, in this theory and studied some physical and geometrical properties.     

On the V/Vm test for a recently published list of bright QSO's

When the V/V_m test is appropriately applied to a recently-published list of bright QSO's the result is closely consistent with the local hypothesis of the nature of QSO's. When an appropriate plot of these QSO's is made in a redshift-magnitude diagram there is no evidence of the density of points increasing reciprocally with flux, as it must do according to the cosmological theory. This new data, therefore, confirms the disproof of the cosmological theory given in Cardiff Preprint No. 88.     

Accelerated expansion from non-linear derivative interaction and Gauss–Bonnet invariant

We discuss in this letter a new cosmological model including both a non-linear derivative interaction and a Gauss–Bonnet invariant. The first interaction term appears in the theory with the Galilean shift symmetry, whereas the second term is motivated from string theory and plays a crucial role in Chern–Simons gravitational theories as well as in the renormalization of quantum field theories in curved spacetime. It is shown that the presence of both the cubic interaction and the Gauss–Bonnet invariant term supply amazingly prosperous cosmological phenomenologies, which are explored in some detail.     

Perihel-Bewegung und kosmologische Singularität in TREDERS Gravitationstheorie

In the framework of TREDER 's gravitational theory we elaborate the consequences of a class of field equations for some solar-system effects and their connection to the problem of cosmological singularity. These equations read on special conditions with components of the energy momentum tensor, KRONECKER 's symbol, tetrad components). ω is a real parameter. If we choose the integration constants of the static spherically symmetric vacuum case in such a way that red shift is the same like that of EINSTEIN 's theory and the source of gravitational field is that of a point mass we obtain for the perihelion rotation the expression is EINSTEINS value of the perihelion rotation.) For we obtain But only if ω > 2/5 cosmological models exist which have no cosmological singularity. On the other hand for ω > 2/5 the value is greater than.     

Varying Fundamental Constants from a String-inspired Brane World Model

We report results on the construction of cosmological braneworld models in the context of the Einstein-Gauss-Bonnet gravity, which include the leading correction to the Einstein-Hilbert action suggested by superstring theory. We obtain and study the equations governing the dynamics of the standard cosmological models. We find that they can be written in the same form as in the case of the Randall-Sundrum model but with time-varying four-dimensional gravitational and cosmological constants. Finally, we discuss the cosmological evolution predicted by these models and their compatibility with observational data. This revised version was published online in July 2006 with corrections to the Cover Date.     

Micro and Macro Cosmological Model in Barber's Second Self-Creation Theory

A spatially homogeneous anisotropic Bianchi type-I cosmological model in the Barber's second self-creation theory is constructed when the gravitational field is generated by a mixture of micro and macro matter fields represented by meson field and perfect fluid respectively. The physical and geometrical features of the micro and macro cosmological model are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

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 missing mass problem and the cosmological constant problem in the Brans-Dicke theory

The missing mass problem and the cosmological constant problem, which arised in the theory of general relativity, are re-examined in the Brans-Dicke theory. It is shown that the two problems can be solved in simple ways in the Brans-Dicke theory.     

An inflationary cosmological model in Dunn's scalar-tensor theory of gravitation

The gravitational field equations in Dunn's scalar-tensor theory of gravitation are generalized by including a cosmological constant. The resulting equations are solved for a Robertson-Walker line-element with flat three-space. The solution represents a cosmological model that develops into an inflationary era.