Ghosts in the self-accelerating DGP branch with Gauss-Bonnet effect
  The Dvali-Gabadadze-Porrati brane-world model provides a possible approach to address the late-time cosmic acceleration. However, it has subsequently been pointed out that a ghost instability will arise on the self-accelerating branch. Here, we carefully investigate whether this ghost problem could be possibly cured by introducing the Gauss-Bonnet term in the five-dimensional bulk action, a natural generalization to the Dvali-Gabadadze-Porrati model. Our analysis is carried out for a background where a de Sitter brane is embedded in an anti-de Sitter bulk. Our result shows that the ghost excitations cannot be avoided even in this modified model. 
Yen-Wei Liu, Keisuke Izumi, Mariam Bouhmadi-Lopez, Pisin Chen
hep-th astro-ph.CO gr-qc