Global Structure of Symmetries in Particle Physics

Seth Koren shows how global symmetry structure and field-space topology affect particle-physics predictions beyond the usual analysis of small field fluctuations. Different possible global forms of the Standard Model gauge group imply different model-independent predictions for fractionally charged particles. Collider searches for these particles could identify the gauge-group structure and exclude unification models. The talk then examines axion theories, using the DFSZ model to show how the global properties of scalar fields and gauge symmetries modify axion strings and can resolve the cosmological domain-wall problem.