Symmetry adapted states for Hubbard clusters

The application of spin, pseudo spin and space group symmetry to find symmetry adapted states for the square planar Hubbard model is discussed. An approach based on pseudo spin configurations and the application of Young tableaux to the permutation group is presented. The method is illustrated for the case of a 4*4 cluster and the complete classification of the states for this cluster is given. It is shown that the linear dimension of the largest matrix block is reduced by three orders of magnitude by application of the above symmetries. (C) 1998 American Institute of Physics. [S0022-2488(98)00612-4].