Wormholes and Cosmic Strings

A gravitational scenario is proposed where the euclidean action is invariant under the isotropic and homogeneous version of the euclidean U(1) group of local transformations of the scale factor and scalar matter field, interpreting the trace of the second fundamental form as the gauge field. The model allows spontaneous breakdown of some involved symmetries, including possibly diffeomorphism invariance, and leads to the formation of topological deffects. In particular, we consider here the case of the wormhole-induced formation of cosmic strings.