Non-singular solutions in multidimensional cosmology with perfect fluid: acceleration and variation of \(G\) (Q2457712)

Some time ago (in the mid thirties of the 20th century) Milne and Dirac had discussed cosmological models containing gravitational constant weakly changing in time. The paper deals with consequences of such an assumption by considering the dynamics of an ideal fluid cosmological models both isotropic and anisotropic. Irrespective to anisotropy (that is for the general anisotropic case) the authors obtained two solutions with accelerated expansion of our 3-space in which the obtained changes in the gravitational constant are negligibly small. The solutions depend upon the parameter \(w\) controlling the pressure. For \(w>1\) the obtained solution is describing the ``superstiff'' matter while for \(w<-1\) the solution is describing a phantom matter. Exact definitions of these two regimes are given in the paper.