Root system Φ in Euclidean space: finite reflection-stable system. Weyl group W = ⟨reflections through roots⟩ permutes Φ. Crystallographic root systems classified by Cartan matrix. Foundational for Lie groups + quantum groups + Coxeter…
Root system Φ in Euclidean space: finite reflection-stable system. Weyl group W = ⟨reflections through roots⟩ permutes Φ. Crystallographic root systems classified by Cartan matrix. Foundational for Lie groups + quantum groups + Coxeter…