Wormhole on DGP brane
  We analyze a spacetime structure on a new brane configuration constructed recently in the Dvali-Gabadadze-Porrati braneworld context. The brane, embedded on a five-dimensional bubble of nothing, has a wormhole structure. It is an exact solution without any matter fields, and thus the energy conditions for matter fields are trivially satisfied. We see that, under the traversability condition, the size of the bubble should be larger than 10^{10}cm or so. 
Yoshimune Tomikawa, Tetsuya Shiromizu, Keisuke Izumi
gr-qc