Wormholes and compactification

The possibility of connecting a region where some dimensions are compact to another region where compactification does not exist is examined in the context of some simple models. There we find the matching of compactified to uncompactified space, through a wall of positive energy density per unit surface, given that the Einstein's equations hold, implies the existence of a wormhole. The possibility of spontanous nucleating a phase of compactified space in the midst of an uncompactified one is briefly discussed. (author)