 Peter–Weyl theorem

The Peter–Weyl theorem is a fundamental result in the representation theory of compact topological groups. It describes how the regular representation of a compact group can be decomposed into irreducible representations. Here's a brief overview of the main points of the theorem: 1. **Compact Groups**: The theorem applies specifically to compact groups, which are groups that are also compact topological spaces. Examples include \(SU(n)\), \(SO(n)\), and \(U(n)\).