Towards a qualitative understanding of the scattering of topological defects

Head-on collisions of strings, monopoles, and Skyrmions result in 90° scattering. We propose a unified description of these objects (for the global case) as members of a definite class of topological defects. All soliton-soliton pairs that are members of this class scatter at 90° in head-on collisions. Our analysis also shows that the scattered solitons are composed of half-portions of the original solitons. We further predict back-to-back scattering for head-on collisions of a soliton-antisoliton pair at sufficiently high energies. We argue that these qualitative aspects of scattering are common because strings, monopoles, and Skyrmions correspond to various winding-number mappings from $S^n$ to $S^n$. Our analysis concentrates on the smoothness of the field configurations and may be extendible to the scattering of gauged topological defects. For the case of strings our results lead to an understanding of intercommutivity and the accompanying formation of kinks.