Gauss-Bonnet braneworld redux: A novel scenario for the bouncing universe

We propose a new scenario for the bouncing universe in a simple five-dimensional braneworld model in the framework of Einstein-Gauss-Bonnet gravity, which works even with ordinary matter on the brane. In this scenario, the so-called branch singularity located at a finite physical radius in the bulk spacetime plays an essential role. We show that a three-brane moving in the bulk may reach and pass through it in spite of the fact that it is a curvature singularity. The bulk spacetime is extended beyond the branch singularity in the C^0 sense and then the branch singularity is identified as a massive thin shell. From the bulk point of view, this process is the collision of the three-brane with the shell of branch singularity. From the point of view on the brane, this process is a sudden transition from the collapsing phase to the expanding phase of the universe. The present result opens a completely new possibility to achieve the bouncing brane universe as a higher-curvature effect.