Brans-Dicke Scalar-tensor Theory Of Gravitation Research Articles

Brans-Dicke accelerated cosmologies with fermionic sources

In the framework of the Brans-Dicke scalar-tensor theory of gravitation, we investigate the role of a self-interacting fermionic field in a universe filled with dust and radiation constituents. This model is shown to present a variety of behaviors, depending on the parameters chosen. In particular, we find that the fermionic field is capable of promoting a transition from an initially decelerated, radiation-dominated period to a later accelerated regime where the fermion prevails. The Brans-Dicke field is found to approach a constant value, and an intermediary matter-dominated era is observed. The dependence of the acceleration on the fermionic potential was also investigated. On a second analysis, the possibility of a direct energy exchange between the constituents was considered, using the dynamical pressure approach. On this later formulation a three-era cosmological regime emerged.

Dark Range of ω In Brans-Dicke Gravity

The variational field equations of Brans-Dicke scalar-tensor theory of gravitation that is coupled to a mass-varying sterile neutrino field are presented in Riemannian and non-Riemannian setting in the language of exterior differential forms over four-dimensional spacetime. In a gravitational plane wave geometry in Rosen coordinates, with the scalar field set equal to a constant, the field equations admit ghost neutrino solutions. These correspond to Majorana spinor configurations for which the total neutrino stress-energy-momentum tensor vanishes. We show here that in the absence of a sterile neutrino in the gravitational wave geometry, there are scalar field configurations for which the total scalar field stress-energy-momentum tensor vanishes for negative values of the Brans-Dicke parameter —3/2 < ω < 0.

Astronomical tests of relativity: beyond parameterized post-Newtonian formalism (PPN), to testing fundamental principles

AbstractBy the early 1970s, the improved accuracy of astrometric and time measurements enabled researchers not only to experimentally compare relativistic gravity with the Newtonian predictions, but also to compare different relativistic gravitational theories (e.g., the Brans-Dicke Scalar-Tensor Theory of Gravitation). For this comparison, Kip Thorne and others developed the Parameterized Post-Newtonian Formalism (PPN), and derived the dependence of different astronomically observable effects on the values of the corresponding parameters.Since then, all the observations have confirmed General Relativity. In other words, the question of which relativistic gravitation theory is in the best accordance with the experiments has been largely settled. This does not mean that General Relativity is the final theory of gravitation: it needs to be reconciled with quantum physics (into quantum gravity), it may also need to be reconciled with numerous surprising cosmological observations, etc. It is, therefore, reasonable to prepare an extended version of the PPN formalism, that will enable us to test possible quantum-related modifications of General Relativity.In particular, we need to include the possibility of violating fundamental principles that underlie the PPN formalism but that may be violated in quantum physics, such as scale-invariance, T-invariance, P-invariance, energy conservation, spatial isotropy violations, etc. In this paper, we present the first attempt to design the corresponding extended PPN formalism, with the (partial) analysis of the relation between the corresponding fundamental physical principles.

Nonexistence of Plane Symmetric String Cosmological Model in Brans-Dicke Theory of Gravitation

Field equations in Brans-Dicke scalar-tensor theory of gravitation are obtained with the aid a non-static plane symmetric metric in the presence of massive string source. It is shown that a non-static string model, in this theory, does not exist when the sum of the energy density and the tension density of the cosmic string vanishes.

Exact Brans-Dicke-Bianchi type-V solutions

AbstractSpatially homogeneous cosmological models of the Bianchi type-V are considered in the Brans-Dicke scalar-tensor theory of gravitation. Exact solutions are given in the vacuum case as well as for models filled with dust, radiation or stiff matter.

Exact Brans-Dicke-Bianchi Type-II Solutions

Exact solutions of Bianchi type-II models are obtained in the Brans-Dicke scalar-tensor theory of gravitation. The behaviour of the solutions near the initial singularity and at later stages of the expansion is discussed.

Equations governing the oscillations of a self-gravitating elastic sphere under the influence of gravitational waves

We consider the influence of a plane gravitational wave on the following Newtonian system: a self-gravitating elastic sphere without rotation. We determine the equation governing the elastic oscillations within the framework of the general relativity. We include dissipative processes by using a simple relativistic model of viscoelasticity. If the wavelength is much larger than the dimension of the elastic sphere, we transform these equations into the form derived by Ashby and Dreitlein previously. We also determine the equations governing the elastic oscillations within the framework of the Brans-Dicke scalar-tensor theory of gravitation.

Field of a charged particle in Brans-Dicke theory of gravitation

Field equations in the Brans-Dicke scalar-tensor theory of gravitation are obtained for a static charged point mass with the aid of a spherically symmetric conformally flat 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 in a conformally flat space.