Strong coupling in brane-induced gravity in five dimensions

Brane-induced gravity in five dimensions (Dvali–Gabadadze–Porrati model) exhibits modification of gravity at ultra-large distances, r ≫ rc = M 2 P l/M 3 where M is the five-dimensional gravity scale. This makes the model potentially interesting for explaining the observed acceleration of the Universe. We argue, however, that it has an intrinsic intermediate energy scale (M9/M4 P l) 1/5. At higher energies, the model is strongly coupled. For rc of order of the present Hubble size, the strong coupling regime occurs at distanced below tens of metres.