Vertex-algebraic structure of principal subspaces of the basic modules for twisted affine Lie algebras of type A2n−1(2),Dn(2),E6(2)

We obtain a presentation of principal subspaces of the basic modules for the twisted affine Kac-Moody Lie algebras of type A2n−1(2), Dn(2) and E6(2). Using this presentation, we construct exact sequences among these principal subspaces, and use these exact sequences to obtain recursions satisfied by graded dimensions of the principal subspaces. Solving these recursions, we obtain the graded dimensions of the principal subspaces.