Vacuum instability in the presence of solitons

Metastable vacua appear in many models of high energy physics such as supersymmetry breaking models. Stability of the false vacua against quantum tunneling is usually assumed to be sufficient to ensure viability of such models. In this talk, I discuss a new type of classical instability of the false vacuum when topological solitons are present. If the topology of the vacuum manifold allows for the existence of defects such as cosmic strings or monopoles, the true vacuum can be "seeded" within the cores of these defects and render the false vacuum parametrically unstable. I discuss two recently published examples of such instabilities.