Towards the spectrum of a GUT from gauge invariance

Understand

The description of electroweak physics using perturbation theory is highly successful.

• Though not obvious, this is due to a subtle field-theoretical effect, the Fr\"ohlich-Morchio-Strocchi mechanism, which links the physical spectrum to that of the elementary particles.
• This works because of the special structure of the standard model, and it is not a priori clear whether it works for structurally different theories.
• Candidates for conflicts are, e.g., grand unified theories.