Brans–Dicke theory

The Brans Dicke theory ( sometimes referred to as Jordan - Brans Dicke theory ) is a classical field theory and one of the simplest extensions of General Relativity (GR ). It was developed in 1961 by Robert Henry thickness and Carl H. Brans, which they used earlier work by Pascual Jordan. It is the best known and simplest representative of so-called scalar - tensor theories of gravitation. These are gravitational theories in which in addition to the metric of the scalar fields ART additional problems that - generate the curvature of space - together with the metric occurring in the ART.

The theory contains a free parameter and approaches for up to indistinguishability of ART, so that it can not be falsified in principle experiments. But precision measurements during the Cassini - Huygens mission have shifted the allowed range on a big step from the previous strongest results.

Definition

The effect of Brans Dicke theory is

Here g is the metric, R is the trace of the Ricci tensor, a dimensionless parameter, a scalar field and the effect of matter fields, which is assumed to be independent of.

In contrast to the type in which the effect is given by, there is an additional scalar field that couples over the curvature. This leads to modified motion equations:

Wherein the energy -momentum tensor and T is its trace. T is, according to the first equation is a source of the scalar field, which, as shown in the second equation, contributes to the curvature. This is different from the theory of the type in which the equations of motion are represented by. This modification leads to a change predictions for certain gravitational effects such as the deflection of light by massive bodies or the perihelion of the planet. Through experiments were therefore the allowed values ​​for the coupling constant which can be chosen as a free parameter and controls the size of the deviations from the predictions of GR are very limited.