Models of G time variations in diverse dimensions

TL;DR

This paper reviews various cosmological models across different dimensions that can explain the small observed time variation of the gravitational constant G, highlighting theoretical approaches compatible with current data.

Contribution

It compares multiple multidimensional and scalar-tensor models to identify mechanisms that account for G's small time variation consistent with observations.

Findings

Multiple models can explain small G variation

Scalar-tensor and multidimensional models are viable

Experimental bounds on G-dot are satisfied in various scenarios

Abstract

A review of different cosmological models in diverse dimensions leading to a relatively small time variation of the effective gravitational constant G is presented. Among them: 4-dimensional general scalar-tensor model, multidimensional vacuum model with two curved Einstein spaces, multidimensional model with multicomponent anisotropic "perfect fluid", S-brane model with scalar fields and two form field etc. It is shown that there exist different possible ways of explanation of relatively small time variation of the effective gravitational constant G compatible with present cosmological data (e.g. acceleration): 4-dimensional scalar-tensor theories or multidimensional cosmological models with different matter sources. The experimental bounds on G-dot may be satisfied ether in some restricted interval or for all allowed values of the synchronous time variable.