We review some applications of relativistic shells that are relevant in the
context of quantum gravity/quantum cosmology. Using a recently developed
approach, the stationary states of this general relativistic system can be
determined in the semiclassical approximation. We suggest that this technique
might be of phenomenological relevance in the context of the brane-world
scenario and we draw a picture of the general set-up and of the possible
developments.Comment: 4 pages, LaTeX. To appear in the proceedings of the Eleventh Marcel
Grossmann Meeting on General Relativity, July 23-29, 2006, Freie Universitaet
Berlin, Berlin, Germany (http://www.icra.it/mg/mg11