Properties ofZ2strings

We discuss various properties of cosmic strings formed by symmetry breaking of the form G→K×$Z_2$. The unbroken $Z_2$ can be embedded in different U(1) subgroups of G, giving topologically equivalent but dynamically different strings. We obtain the string mass in terms of the Higgs-field vacuum expectation value for various values of the gauge and quartic Higgs-field coupling constants by numerical calculation. We find that in a wide range of realistic cases, unless there is an intermediate K×U(1) phase, the lowest-mass embedding gives strings which are gauge equivalent to antistrings, in which case the beadlike solitons of Hindmarsh and Kibble do not occur.