A photon mass on the brane

We discuss the impact of a bulk photon mass in a Dvali–Gabadadze–Porrati type brane model with Maxwell terms both on the brane and in the bulk, as proposed by Dvali, Gabadadze and Shifman. The motivation to include the bulk photon mass is to suppress radiation loss into the bulk. We point out that this modifies the photon propagator in such a way that it generates a small photon mass on the brane. Compatibility with present bounds on a photon mass imply that the transition to five-dimensional distance laws for the electromagnetic potentials would appear only at super-horizon length scales, thus excluding any direct detection possibility of a transition from four-dimensional to five-dimensional distance laws in electromagnetic interactions. We also include results on fermion propagators with Dirac terms on the brane and in the bulk.