SEMILOCAL TOPOLOGICAL DEFECTS

Semilocal defects are those formed in field theories with spontaneously broken symmetries, where the vacuum manifold M is fibred by the action of the gauge group in a non-trivial way. Studied in this paper is the simplest such class of theories in which M congruent-to S2N-1, fibred by the action of a local U(1) symmetry. Despite M having trivial homotopy groups up to pi2N-2, this theory exhibits a fascinating variety of defects: vortices, or semilocal strings; monopoles (on which the strings terminate); and (when N = 2) textures, which may be stabilised by their associated magnetic field to produce a skyrmion.