The formation rate of semilocal strings
  We carry out three-dimensional numerical simulations to investigate the formation rate of semilocal strings. We find that the back-reaction of the gauge fields on the scalar field evolution is substantial, and leads to a significant formation rate in the parameter regime where the semilocal strings are classically stable. The formation rate can be as large as a third of that for cosmic strings, depending on the model parameters. 
Ana Achucarro, Julian Borrill and Andrew R Liddle