Perturbative estimates suggest that extended topological defects such as cosmic strings emit few particles, but numerical simulations of the fields from which they are constructed suggest the opposite. In this paper we study the decay of the two-dimensional prototype of strings, domain walls in a simple scalar theory, solving the underlying quantum field theory in the Hartree approximation. We conclude that including the quantum effects makes the picture clear: the defects do not directly transform into particles, but there is a nonperturbative channel to microscopic classical structures in the form of propagating waves and persistent localized oscillations, which operates over a huge separation of scales. When quantum effects are included, the microscopic classical structures can decay into particles
