Combinatorial bases of principal subspaces for the affine Lie algebra of type

We consider principal subspaces WL(kΛ0) and WN(kΛ0) of standard module L(kΛ0) and generalized Verma module N(kΛ0) at level k≥1 for the affine Lie algebra of type . By using the theory of vertex operator algebras, we find combinatorial bases of principal subspaces in terms of quasi-particles. From quasi-particle bases, we obtain character formulas for WL(kΛ0) and WN(kΛ0).