Linked from
The 30 pages that link to Representation theory, each with the reason it gives.
Gauge theoryRelated: Matter fields transform in representations of the gauge group.
Group theoryRelated: Representations turn group operations into matrices that can be analyzed.
Lie groupRelated: Representations turn Lie group symmetries into linear actions on vector spaces.
Hermann WeylRelated: Weyl used representations to classify symmetries and organize quantum states.
Emil ArtinRelated: Artin’s work connected group representations with L-functions and arithmetic.
Ado's theoremNarrower topic: Ado's theorem is an existence result at the foundation of this field.