Topological defects with a nonsymmetric core

We demonstrate that field theories involving explicit breaking of continous symmetries incorporate two generic classes of topological defects each of which is stable for a particular range of parameters. The first class includes defects of the usual type where the symmetry gets restored in the core and vacuum energy gets trapped there. We show, however, that these defect solutions become unstable for certain ranges of 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 case, initially spherical, bubblelike configurations are simulated numerically and shown to evolve generically towards a planar collapse. In the string case, the decay of the symmetric core vortex resembles the decay of a semilocal string to a Skyrmion with the important difference that while the Skyrmion is unstable and decays to the vacuum, the resulting nonsymmetric vortex is topologically stable.