No abstract

We investigate, in the context of five-dimensional (5D) Brans-Dicke theory of gravity, the idea that macroscopic matter configurations can be generated from pure vacuum in five dimensions, an approach first proposed by Wesson and collaborators in the framework of 5D general relativity. We show that the 5D Brans-Dicke vacuum equations when reduced to four dimensions (4D) lead to a modified version of Brans-Dicke theory in 4D. As an application of the formalism, we obtain two 5D extensions of 4D O'Hanlon and Tupper vacuum solution and show that they lead two different cosmological scenarios in 4D.

It is shown that in the weak field approximation solutions of Brans-Dicke equations are simply related to the solutions General Relativity equations for the same matter distribution. A simple method is developed which permits to obtain Brans-Dicke solutions from Einstein solutions when both theories are considered in their linearized forms. To illustrate the method some examples found in the literature are discussed.

The gravitational field of cosmic vacuum strings and domain walls in the context of Brans–Dicke theory of gravity are investigated. Using the weak field approximation, the solutions which describe the space–time and the scalar field generated by these topological structures are found, the results are compared with the ones obtained in General Relativity.

The gravitational field of a global monopole in the context of Brans-Dicke theory of gravity is investigated. The space-time and the scalar field generated by the monopole are obtained by solving the field equations in the weak field approximation. A comparison is made with the corresponding results predicted by General Relativity.