TOPOLOGICAL DEFECTS WITH A NONSYMMETRIC CORE

We demonstrate that field theories involving explicit breaking of cont inous symmetries incorporate two generic classes of topological defect s each of which is stable for a particular range of parameters. The fi rst class includes defects of the usual type where the symmetry gets r estored in the core and vacuum energy gets trapped there. We show, how ever, that these defect solutions become unstable for certain ranges o f parameters and decay not to the vacuum but to another type of stable defect where the symmetry in not restored in the core. In the wall ca se, initially spherical, bubblelike configurations are simulated numer ically and shown to evolve generically towards a planar collapse. In t he string case, the decay of the symmetric core vortex resembles the d ecay of a semilocal string to a Skyrmion with the important difference that while the Skyrmion is unstable and decays to the vacuum, the res ulting nonsymmetric vortex is topologically stable.