In models involving more than one U(1)’-charged scalar field (as is often the case in grand unified theories) the cosmic strings which emerge may be more complicated than simple Nielsen-Olesen flux tubes. In particular, strings can form with domain walls or with log-infinite contributions to the mass. A universe with these strings is very different from one in which there are only Nielsen-Olesen-type flux tubes.

• Received 3 May 1988

DOI:https://doi.org/10.1103/PhysRevD.38.1100