Skyrmions and monopoles - isolated and arrayed

There are two basic types of three-dimensional topological soliton, namely skyrmions and monopoles. This article reviews some of the features of such solitons, concentrating on static multi-skyrmions and multi-monopoles with structure group SU(2), and focusing in particular on periodic arrays. An isolated multi-skyrmion typically has a regular, for example polyhedral, structure; and there are multi-monopoles which look very similar. However, when it comes to infinite arrays of solitons - chains, walls or crystals - then the skyrmion and monopole systems behave rather differently.