On the formation of non-topological string networks

We review recent simulations of the formation of a particular class of non-topological defects known as semilocal strings during a phase transition. Semilocal strings have properties that are intermediate between topological cosmic strings and stable electroweak strings, and therefore the observation that they could form in substantial quantities during a cosmological phase transition has implications for structure formation, baryogenesis, etc. At the same time, and from a purely theoretical point of view, they provide a very good testing ground for investigating the role of gauge fields in defect formation. (C) 1998 Published by Elsevier Science B.V. All rights reserved.