Local gauge invariance and formation of topological defects

In superconductors. and in other systems with a local U(1) gauge invariance , there are two mechanisms that form topological defects in phase transitio ns. In. addition to the standard Kibble mechanism, thermal fluctuations of the magnetic field also lead to defect formation. This mechanism is specifi c to local gauge theories, predicts a qualitatively different spatial defec t distribution and is the dominant source for topological defects in slow t ransitions. I review the arguments that lead to these conclusions and discu ss possibilities of testing the scenario in superconductor experiments.