Tolman's formula in scalar-tensor theories of gravitation

Erevan State University; Institute of Applied Problems of Physics, Armenian Academy of Sciences. Translated from Astrofizika, Vol. 34, No. 2, pp. 265–270, March–April, 1991.     

Integral conservation laws in bimetric scalar-tensor theory

We have obtained covariant expressions for conserved 4-momentum and angular momentum in a gravitational field with matter within the framework of the bimetric scalar-tensor theory of gravitation. These quantities are represented as surface integrals, allowing us to calculate their values using only data in the asymptotic region far from the source.Translated from Astrofizika, Vol. 37, No. 1, pp. 167–173, January–March, 1994.     

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.     

Cosmological models in certain scalar-tensor theories

Exact solutions of Einstein field equations are obtained in the scalar-tensor theories developed by Saez and Ballester (1985) and Lau and Prokhovnik (1986) when the line-element has the form $$ds^2 = \exp \left( {2h} \right)dt^2 - \exp \left( {2A} \right)\left( {dx^2 + dy^2 } \right) - \exp \left( {2B} \right)dz^2 $$ whereh, A andB are functions oft only. The solutions are spatially homogeneous, locally rotationally symmetric and admit a Bianchi I group of motions on hypersurfacest = constant. The dynamical behaviours of these models have also been discussed.     

Emission of gravitational waves in the scalar-tensor theory of gravitation

Erevan State University. Translated from Astrofizika, Vol. 36, No. 3, pp. 323–430, July–September, 1993.     

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.     

On stationary axially symmetric solutions of a scalar-tensor theory of gravitation

In this paper we obtain the general axially symmetric space-times in scalar-tensor theory of gravitation proposed by Sáez and Ballester. The only possible solutions of these space-times in this theory are dust solutions. One of the obtained solutions here has a similar considerations to Van Stockum dust solution. A detailed study of geometric and kinematical properties of the obtained solutions are carried out. Furthermore, closed timelike curves are present in these solutions.     

An anisotropic cosmological model in a scalar-tensor theory of gravitation

A spatially-homogeneous and anisotropic-cosmological model in a scalar-tensor theory proposed by Sen and Dunn (1971) is obtained when the source of the gravitational field is a perfect fluid with pressure equal to energy density and the metric is of Bianchi type-I. Various physical properties of the model have also been discussed.     

Field of a charged particle in a scalar-tensor theory of gravitation

Field equations in the scalar-tensor theory of gravitation, proposed by Saez and Ballester (Phys. Lett. A 113: 467, 1986), are obtained for a static charged point mass with the aid of a spherically symmetric metric. A closed form exact solution of the field equations is presented and may be considered as describing the field due to a charged mass point at the origin surrounded by a scalar-tensor field.     

Exact Bianchi type-II vacuum-cosmological model in a scalar-tensor theory of gravitation

An exact Bianchi type-II vacuum-cosmological model is obtained in the scalar-tensor theory of gravitation proposed by Dunn. The behaviour of the model is discussed.     

Conformally flat static space-time in the general scalar-tensor theory of gravitation

Explicit vacuum field equations in the general scalar-tensor theory of gravitation proposed by Nordtvedt are obtained with the aid of the most general conformally flat spherically-symmetric static space-time. It is shown that the most general conformally flat spherically-symmetric static solution of Nordtvedt-Barker vacuum field equations is simply the empty flat space-time of general relativity.     

Five dimensional dark energy model in a scalar-tensor theory of gravitation

A five dimensional Kaluza-Klein dark energy model with variable equation of state (EoS) parameter and a constant deceleration parameter is presented in Saez and Ballester (Phys. Lett. A 113:467, 1986) scalar-tensor theory of gravitation. Some physical and kinematical properties of the model are also discussed.     

Bianchi type-VI0 vacuum model in the general scalar-tensor theory of gravitation

The spatially-homogeneous and anisotropic Bianchi type-VI₀ cosmological model is obtained in the Nordtvedt-Barker general scalar-tensor theories of gravitation. Exact solutions of the Nordtvedt-Barker field equations in vacuum are presented and studied.     

Bianchi type-IX cosmic strings in a scalar-tensor theory of gravitation

Bianchi type-IX space-time is considered in the presence of cosmic string source in the frame work of a scalar- tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1985). Exact cosmological models representing geometric (Nambu) string, p string and baratropic string are discussed in this theory. Some physical and kinematical properties of the models are also studied.     

Five dimensional string cosmological models in a scalar-tensor theory of gravitation

Five dimensional Kaluza-Klein space-time is considered in the presence of cosmic string source in the frame work of scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113, 467 (1985)). Exact cosmological models, which represent Nambu, Takabayasi and Reddy strings are presented. Some physical and kinematical properties of the models are also discussed.     

Some plane symmetric inhomogeneous cosmological models in the scalar-tensor theory of gravitation

The present study deals with the inhomogeneous plane symmetric models in scalar-tensor theory of gravitation. We used symmetry group analysis method to solve the field equations analytically. A new class of similarity solutions have been obtained by considering the inhomogeneous nature of metric potential. The physical behavior and geometrical aspects of the derived models are also discussed.     

The equivalence between General Relativity and scalar-tensor theories of gravity

The equivalence between General Relativity and scalar-tensor theories is discussed. Vacuum solutions of the Brans-Dicke theory of gravity are shown to behave ambiguously whenever attempts are made to interpret them as Einstein's solutions generated by an effective energymomentum tensor.Work supported by CNPq, Brazil     

On birkhoff’s theorem in the bimetric scalar-tensor theory of gravitation

It is shown that in the most general version of the bimetric scalar-tensor theory of gravitation, a spherically symmetric vacuum gravitational field is static if the gravitational scalar does not depend on time. This result is generalized to certain cases in which a source is present, including an electromagnetic field. Both branches of solutions with a variable and a constant scalar field are considered. Translated from Astrofizika, Vol. 40, No. 2, pp. 281–290, April–June, 1997.     

Bianchi type-VI0 cosmological model in the general scalar-tensor theory of gravitation

The exact Bianchi type-VI₀ stiff-fluid cosmological model is obtained in the Nordtvedt-Barker general scalar-tensor theory of gravitation. Some properties of the model are discussed.