  Motivated by stringy considerations, Randall & Sundrum have proposed a model
where all the fields and particles of physics, save gravity, are confined on a
4-dimensional brane embedded in 5-dimensional anti-deSitter space. Their
scenario features a stable bound state of bulk gravity waves and the brane that
reproduces standard general relativity. We demonstrate that in addition to this
zero-mode, there is also a discrete set of metastable bound states that behave
like massive 4-dimensional gravitons which decay by tunneling into the bulk.
These are resonances of the bulk-brane system akin to black hole quasinormal
modes--as such, they give rise to the dominant corrections to 4-dimensional
gravity. The phenomenology of braneworld perturbations is greatly simplified
when these resonant modes are taken into account, which is illustrated by
considering gravitational radiation emitted from nearby sources and early
universe physics.
