Dark energy in five-dimensional Brans-Dicke cosmology with dimensional reduction

We explore a 5D Brans-Dicke scalar cosmology by conjecturing that the four-dimensional Hubble parameter varies as H =εφs,ε ∈ R and s is some unknown power index and that the extra-dimensions compactify as the visible dimensions expand as b(t) ≈ ax(t),x ∈ R-.We mainly discuss the case x =-1.For critical values of ε close to unity,it was observed that the acceleration of the universe occurs at redshift close to z =0.8 which indicates that in our model,accelerated expansion of the universe began only recently.Several interesting points are revealed and discussed in some detail.