Superconducting cosmic strings in grand unified models

Witten's U(1)xU(1) superconducting string is re-examined under more general assumptions and is shown to carry a component of unbroken U(1) flux. Embedding the model in a theory with a larger symmetry reveals that generally there are many solutions, obtainable from the original by group transformations, which under certain circumstances lie in a complete representation. Interpolation between different core fields along the string produces monopole-like lumps which do not permit the passage of current. Some cosmological implications are briefly discussed. (orig.)