Narrow Results

The cosmological observation indicates that the effective equation of state parameter w_eff varies with z: it changes from w_eff > -1 to w_eff < -1 at z~0.2. We investigate under which condition it exhibits such behaviors based on the five-dimensional braneworld scenario. It is possible in the model with or without an energy exchange between the four-dimensional universe and the fifth dimension. However the curves of w_eff are quite different between the two cases.

We discuss the exact solutions of brane universes and the results indicate that the Friedmann equations on the branes are modified with a new density term. Then, we assume the new term as the density of dark energy. Using Wetterich's parametrization equation of state (EOS) of dark energy, we obtain that the new term varies with the redshift z. Finally, the evolutions of the mass density parameter Ω₂, dark energy density parameter Ω_x and deceleration parameter q₂ are studied.

We present an alternative geometric derivation of the quantum cosmology arising from a brane universe in the context of geodetic gravity. We set up the Regge–Teitelboim model to describe our universe, and we recover its original dynamics by thinking of such model as a second-order derivative theory. A canonical transformation brings us the internal physical geometry of the theory and induces its quantization straightforwardly.