COHERENT PAIRING STATES FOR THE HUBBARD-MODEL

We consider the Hubbard model and its extensions on bipartite lattices . We define a dynamical group based on the eta-pairing operators intro duced by Yang, and define coherent pairing states, which are combinati ons of eigenfunctions of eta-operators. These states permit exact calc ulations of numerous physical properties of the system, including ener gy, various fluctuations and correlation functions, including pairing off-diagonal long-range order to all orders. This approach is compleme ntary to BCS, in that these are superconducting coherent states associ ated with the exact model, although they are not eigenstates of the Ha miltonian.