The spontaneous breaking of a metastable string

We consider the phase transition of a string with tension $\eps_1$ to a string with a smaller tension $\eps_2$. The transition proceeds through quantum tunneling, and we calculate in arbitrary number of dimensions the pre-exponential factor multiplying the leading semiclassical exponential expression for the rate of the process. At $\eps_2=0$ the found formula for the decay rate also describes a break up of a metastable string into two pieces.