A FAMILY OF AFFINE QUANTUM GROUP INVARIANT INTEGRABLE EXTENSIONS OF THE HUBBARD HAMILTONIAN

We construct a family of spin chain Hamiltonians, which have the affin e quantum group symmetry <Uq(g)over cap>. Their eigenvalues coincide w ith the eigenvalues of the usual spin chain Hamiltonians, but have the degeneracy of levels, corresponding to the affine <Uq(g)over cap>. Th e space of states of these spin chains is formed by the tensor product of the fully reducible representations of the quantum group. The ferm ionic representations of the constructed spin chain Hamiltonians show that we have obtained new extensions of the Hubbard Hamiltonians. All of them are integrable and have the affine quantum group symmetry. The exact ground state of such type of model is presented, exhibiting sup erconducting behavior via the eta-pairing mechanism. (C) 1997 Elsevier Science B.V.