Dynamics of the universe as a "test 3-brane" in a 5D bulk
  In this paper we study the dynamics of a 5D bulk space-time with our universe as a "test 3-brane" located in the bulk, an idealized model of a topological object whose physical properties is negligible in comparison with that of the bulk. Our universe experiences acceleration and its equation of state parameter crosses the phantom divide line due to the geometry of the bulk space-time. 
Hossein Farajollahi, Arvin Ravanpak
gr-qc hep-th