Core Phase Transitions for Embedded Topological Defects

Vortices in superfluid 3He-B have been observed to undergo a core transition. We discuss the analog phenomenon in relativistic field theories which admit embedded global domain walls, vortices and monopoles with a core phase structure. They are present in scalar field theories with approximate global symmetries which are broken both spontaneously and in parts explicitly. For a particular range of parameters their symmetric core exhibits an instability and decays into the nonsymmetric phase.