  We consider the decay of a metastable domain wall. The transition proceeds
through quantum tunneling, and we calculate in arbitrary number of dimensions
the preexponential factor multiplying the leading semiclassical exponential
expression for the rate of the process. We find that the effect of the motion
in transverse directions reduces to a renormalization of the tension of the
edge of the wall in the semiclassical exponent. This behavior is similar to the
one previously found for breaking of a metastable string. However this simple
property is generally lost for spontaneous decay of higher-dimensional branes.
