Compact connected Lie groups are classified, up to isomorphism, by their root data. In the semisimple case this reduces to the familiar lattice data between the root and weight lattices; in the reductive case the ambient lattices in the root datum also record the central torus directions and their relation to the semisimple part.
Knowledge Status
Geometry
Discussion
Root Datum Classification identifies how roots and root data encode compact connected Lie groups. In concrete terms, it formalizes the statement that compact connected Lie groups are classified, up to isomorphism, by their root data..