Brane induced cosmological acceleration and crossing of w_{eff}=-1

Abstract

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 $z\sim 0.2$. 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.