DENSITY-MATRIX RENORMALIZATION-GROUP CALCULATION OF CORRELATION-FUNCTIONS IN THE ONE-DIMENSIONAL HUBBARD-MODEL

We have studied correlation functions of the one-dimensional Hubbard model using the density-matrix numerical renormalization-group approach. The singularity exponents of the momentum distribution at k=k(F) and 3k(F), as well as the power-law singularity of the spin-correlation function, are computed for large U (U/t=10(3)). The momentum-distribution exponent at k=k(F) and the spin-correlation exponent are in agreement with the analytic results, while the calculated exponent for momentum distribution at k=3k(F) is about 3/4, which disagrees with the analytically predicted value 9/8. We also discuss several techniques for an accurate calculation of the correlation functions.