Brane $f(\cal R)$ gravity

We consider a brane world scenario in which the bulk action is assumed to have the form of a generic function of the Ricci scalar $f(\mathcal{R})$ and derive the resulting Einstein field equations on the brane. In a constant curvature bulk a conserved geometric quantity appears in the field equations which can be associated with matter. We present cosmological and spherically symmetric solutions by assuming specific forms for $f(\mathcal{R})$ and show that the former can explain an accelerated expanding universe while the latter may account for galaxy rotation curves.