Universe Evolution in a 5D Ricci-flat Cosmology

We use Wetterich's parameterization equation of state (EOS) of dark energy to a $5D$ Ricci-flat cosmological solution and we suppose the universe contains three major components: matter, radiation and dark energy. By using the relation between the scale factor and the redshift $z$, we show that the two arbitrary functions contained in the $5D$ solution could be solved out analytically in terms of the variable $z$. Thus the whole $5D$ solution could be constructed uniquely if the current values of the three density parameters $\Omega_{m0}$, ${\Omega_{r0}}$, $\Omega_{x0}$, the EOS $w_{0}$%, and the bending parameter $b$ contained in the EOS are all known. Furthermore, we find that all the evolutions of the mass density $\Omega_{m} $, the radiation density ${\Omega_{r}}$, the dark energy density $\Omega_{x}$, and the deceleration parameter $q$ depend on the bending parameter $b$ sensitively. Therefore it is deserved to study observational constraints on the bending parameter $b$.