Bulk observers in nonfactorizable geometries - art. no. 085017

We consider five-dimensional nonfactorizable geometries where the transvers e dimension is bounded and the remaining (parallel) dimensions are not. We study the construction of effective theories at distances much longer than the transverse size. An observer unable to resolve the transverse direction can only measure distances along the parallel dimensions, but the nonfacto rizable geometry makes the length of a curve along the parallel dimension s ensitive to where on the transverse direction the curve lies. We show that long geodesics that differ in their end points only by shifts along the tra nsverse direction all have the same length to within the observer's resolut ion. We argue that this is the correct notion of distance in the effective theory for a bulk observer. This allows us to present a consistent interpre tation of what is measured by observers that live either on a brane or in t he bulk.