Tensor Theory Of Gravitation Research Articles

A Bianchi Type -V Cosmological Model in Brans - Dicke Theory of Gravitation

Bianchi type - V space time is considered in the presence of perfect fluid source in the scalar - tensor theory of gravitation proposed by Brans and Dicke [Phys. Rev.124, 925,1961]. With the help of special law of variation for Hubble’s parameter presented by Bermann [Nuovo Cimento B74, 182, 1983] a cosmological model with negative constant deceleration parameter is obtained in the presence of perfect fluid with disordered radiation. Some physical and kinematical properties of the model are also discussed.

A Cosmological Model with Negative Constant Deceleration Parameter in a Scalar-Tensor Theory

With the help of a special law of variation for Hubble's parameter presented by Bermann [Nuovo Cimento B (1983), 74, 182], a cosmological model with negative constant deceleration parameter is obtained in the framework of Saez-Ballester [Phys. Lett (1985), Al 13, 467] scalar -- tensor theory of gravitation. Some physical and kinematical properties of the model are, also, discussed.

Axially Symmetric String Cosmological Model In Brans-Dicke Theory of Gravitation

By adopting the co-moving coordinate system, an exact axially symmetric cosmological model with string dust cloud source is obtained in the framework of Brans-Dicke [Phys. Rev. 124, 925, (1961) Scalar – tensor theory of gravitation. Some physical and kinematical properties of the model are also discussed.

On Einstein–Rosen Cosmic Strings in a Scalar Tensor Theory of Gravitation

Explicit field equations of a scalar tensor theory of gravitation proposed by Saez and Ballester are obtained with the aid of Einstein–Rosen cylindrically symmetric metric in the presence of cosmic string source. The field equations being highly non–linear static and non–static cases have been considered separately. It is observed that in the static case the geometric strings do not exist while in the non–static case cosmological model does not exist in this theory.

General Relativity and Cosmology Derived From Principle of Maximum Power or Force

The field equations of general relativity are shown to derive from the existence of a limit force or of a limit power in nature. The limits have the value of c^4/4G and c^5/4G. The proof makes use of a result by Jacobson. All known experimental data is consistent with the limits. Applied to the universe, the limits predict its darkness at night and the observed scale factor. Some experimental tests of the limits are proposed. The main counter-arguments and paradoxes are discussed, such as the transformation under boosts, the force felt at a black hole horizon, the mountain problem, and the contrast to scalar--tensor theories of gravitation. The resolution of the paradoxes also clarifies why the maximum force and the maximum power have remained hidden for so long. The derivation of the field equations shows that the maximum force or power plays the same role for general relativity as the maximum speed plays for special relativity.

HIGHER DIMENSIONAL SZEKERES' SPACE–TIME IN BRANS–DICKE SCALAR TENSOR THEORY

The generalized Szekeres family of solution for quasi-spherical space–time of higher dimensions are obtained in the scalar tensor theory of gravitation. Brans–Dicke field equations expressed in Dicke's revised units are exhaustively solved for all the subfamilies of the said family. A particular group of solutions may also be interpreted as due to the presence of the so-called C-field of Hoyle and Narlikar and for a chosen sign of the coupling parameter. The models show either expansion from a big bang type of singularity or a collapse with the turning point at a lower bound. There is one particular case which starts from the big bang, reaches a maximum and collapses with the in course of time to a crunch.

Bianchi type-I cosmological effective stiff fluid model in Saez and Ballester theory

The problem of viscous fluid distribution in Bianchi type I space-time is considered here in a new scalar tensor theory of gravitation proposed by Saez and Ballester (1986). Particular solutions of the field equations are derived assuming the viscous coefficient to be the power functions of energy density. Some physical and geometrical properties of the solutions are also discussed.

A string cosmological model in a scalar – Tensor theory of gravitation

An exact Boanchi type -I string cosmological model is obtained in a scalar-tensor theory of gravitation proposed by Saez and Ballester (1985). Some physical properties of the model are also discussed.

Bianchi VI0cosmological model in Saez and Ballester theory

The problem of perfect fluid distribution in spatially homogeneous and anisotropic Bianchi type VI0 space-time is considered in a scalar tensor theory of gravitation proposed by Saez and Ballester (1985). Exact solutions of the field equations are derived when the metric potentials are functions of cosmic time only. Some physical and geometrical properties of the solutions are also discussed.

QUANTUM COSMOLOGY AND WORMHOLES IN SOME SCALAR–TENSOR THEORIES

We consider quantum cosmology for some scalar–tensor theories of gravitation in the case of homogeneous and isotropic cosmological models. We present quantum solutions corresponding to cosmological term: (i) λ(ϕ) = 0 and (ii) λ(ϕ) = 3qϕ. In the first case we find a solution that can be interpreted as a quantum wormhole since it satisfies the Hawking–Page regularity conditions. Also, we obtain the WKB approximation.

Model neutron stars with a constant scalar field in the bimetric scalar-tensor theory of gravitation. Different versions of the equation of state

In our preceding paper we found solutions for the equations of the bimetric scalar—tensor theory of gravitation for neutron stars, in which the scalar field is constant while the metric tensor satisfies the equations of the general theory of relativity. In the present paper we find analogous solutions for different versions of the equation of state of the matter of a neutron star.

Neutron stars in the bimetric scalar—tensor theory of gravitation. II. solutions with a variable scalar field

Solutions of the equations of the bimetric scalar—tensor theory of gravitation with a variable scalar field are found for configurations of superdense matter with different versions of the equation of state. The possible existence of static superdense and supermassive configurations is established for all of the versions of the equation of state of superdense matter used.

The massless scalar field as an alternative to dark matter

Abstract It is shown that if the scalar gravitational field in the generalized scalar—tensor theory of gravitation is taken into account, the cosmological requirement for the existence of dark matter is less strong.

Dynamics of a self-gravitating thin string in scalar - tensor theories of gravitation

We examine the dynamics of a self-gravitating string in the scalar - tensor theories of gravitation by considering it to be described by a thin tube of matter. For a class of solutions, we obtain in the generic case that the extrinsic curvature of the worldsheet of the central line is null in the limit where the radius of the string tends to zero. However, if we impose a specific constraint on the behaviour of the solution then we find that only the mean curvature of the worldsheet of the central line vanishes, which is just the Nambu - Goto dynamics. This analysis can include the massless dilatonic theories of gravity.

Inflationary Solutions for Higher Dimensional Anisotropic Cosmological Model in Scalar-Tensor Theory II

This is the second paper of the series where we have considered Brans-Dicke (B-D) theory as well as general scalar tensor theory of gravitation in higher dimensional space-time model in the false vacuum state. We have examined whether inflationary solutions are possible both for constant or variable coupling parameter ω. Also the nature of the scalar field and the coupling parameter are discussed in the asymptotic limit.

Inflationary solutions for anisotropic model in scalar-tensor theory

In this paper we have studied B-D theory and general scalar tensor theory of Gravitation for anisotropic cosmological model in the false vacuum state. The possibility of both exponential inflation and power function inflation are examined for constant or variable coupling parameter ω. Also asymptotic limit of the scalar field and ω are discussed.

Exact solutions of a flat cosmological model in BSTT

We solve the cosmological equations for the bimetric scalar—tensor theory of gravitation (BSTT) for a flat model of the Friedmann type with the equation of state p = ae. In the initial stage of expansion, the energy density of the scalar field dominates over the energy density of matter. As a result, the behavior of the solution in this limit does not depend on a. For later stages of expansion of the Universe, the solution obtained goes to a special solution having the form of a power law function of time. In this case, the relative change in the gravitational scalar is proportional to the Hubble parameter. In the limit of large values for the parameter of the theory, only a simple solution with zero value of the constant of integration goes to the corresponding Friedmann solution of general relativity theory.

Inflationary solutions in general scalar tensor theory of gravitation

Extended inflation solution in Brans-Dicke theory given by Mathiazhagan and Johri (MJ) is shown as the unique solution only if the scale factor is assumed to be a power function of the scalar field. Only the consistent solution amongst the set of solutions given by Patra, Roy and Ray is found identical to the MJ solution. Both exponential inflation and power function inflation are studied in general scalar tensor theory where the parameter to is a function of the scalar, field. It is noted that exponential inflation is forbidden in Brans-Dicke theory wherew is a constant.

Axisymmetric stationary vacuum fields in the general scalar tensor theory

It is show that axisymmetric stationary vacuum solutions of the general scalar tensor theory of gravitation proposed by Nordvedt and later discussed by Barker and others can be obtained from the solutions of the axisymmetric stationary Einstein vacuum fields and also from the axisymmetric static vacuum fields of the general scalar tensor theory. The scalar tensor analogue of the Kerr solution has been obtained.

The Palatini variational principle for the general Bergmann–Wagoner–Nordtvedt theory of gravitation

The Hilbert variational principle for the Bergmann–Wagoner–Nordtvedt scalar–tensor theory of gravitation is presented in a general form, yielding the field equations in arbitrary units. Applying then the Palatini method of variation to this action integral, the connection can be shown to be an integrable Weyl connection, even if the matter part contains explicitly the connection coefficients. However, the resulting field equations always appear in the wrong unit system, or turn out to be wrong in a general gauge.