  Over the last few years several extra-dimensional models have been introduced
in attempt to deal with the hierarchy problem. These models can lead to rather
unique and spectacular signatures at Terascale colliders such as the LHC and
ILC. The ADD and RS models, though quite distinct, have many common feature
including a constant curvature bulk, localized Standard Model(SM) fields and
the assumption of the validity of the EH action as a description of
gravitational interactions.
