where Id is the identity operator. Here, the latter interpretation, which follows from (G6), is intended. The highest weight representations of s l ( 2 , C ) are indexed by μ for μ = 0, 1/2, 1,.... (The highest weights are actually 2 μ = 0, 1, 2,..., but the notation here is adapted to that of s o ( 3 ; 1 ) . ) The tensor products of two such complex linear factors then form the irreducible complex linear representations of s l ( 2 , C ) ⊕ ⊕ s l ( 2 , C ) .