Combinatorial Bases of Feigin–Stoyanovsky's Type Subspaces of Level 2 Standard Modules for

Abstract

Let be an affine Lie algebra of type and L(Λ) its standard module with a highest weight vector v Λ. For a given ℤ-gradation , we define Feigin–Stoyanovsky's type subspace as By using vertex operator relations for standard modules we reduce the Ponicaré–Brikhoff–Witt spanning set of W(Λ) to a basis and prove its linear independence by using Dong–Lepowsky intertwining operators.