  We study the long distance behaviour of brane theories with quasi-localized
gravity. The 5D effective theory at large scales follows from a holographic
renormalization group flow. As intuitively expected, the graviton is
effectively four dimensional at intermediate scales and becomes five
dimensional at large scales. However in the holographic effective theory the
essentially 4D radion dominates at long distances and gives rise to scalar
anti-gravity. The holographic description shows that at large distances the GRS
model is equivalent to the model recently proposed by Dvali, Gabadadze and
Porrati (DGP), where a tensionless brane is embedded into 5D Minkowski space,
with an additional induced 4D Einstein-Hilbert term on the brane. In the
holographic description the radion of the GRS model is automatically localized
on the tensionless brane, and provides the ghost-like field necessary to cancel
the extra graviton polarization of the DGP model. Thus, there is a holographic
duality between these theories. This analysis provides physical insight into
how the GRS model works at intermediate scales; in particular it sheds light on
the size of the width of the graviton resonance, and also demonstrates how the
holographic RG can be used as a practical tool for calculations.
