Level three standard modules for A2(2) and combinatorial identities

Abstract We use the Z -algebra theory developed by J. Lepowsky and R. Wilson to study the structure of level three standard modules for the affine Lie algebra A 2 (2) in the principal picture. We get their linear bases in terms of Z -operators. As a consequence we give Z -algebra proofs of the conjectures of Capparelli (1993) on two combinatorial identities.