Series of Lie Groups

For various series of complex semi-simple Lie algebras g(t) equipped with irreducible representations V (t), we decompose the tensor powers of V (t) into irreducible factors in a uniform manner, using a tool we call diagram induction. In particular, we interpret the decompostion formulas of Deligne [4] and Vogel [23] for decomposing g respectively for the exceptional series and k ≤ 4 and all simple Lie algebras and k ≤ 3, as well as new formulas for the other rows of Freudenthal’s magic chart. By working with Lie algebras augmented by the symmetry group of a marked Dynkin diagram, we are able to extend the list [2] of modules for which the algebra of invariant regular functions under a maximal nilpotent subalgebra is a polynomial algebra. Diagram induction applied to the exterior algebra furnishes new examples of distinct representations having the same Casimir eigenvalue.