A numerical approach to ground-state dynamical correlation functions from
Density Matrix Renormalization Group (DMRG) is developed. Using sum rules,
moments of a dynamic correlation function can be calculated with DMRG, and with
the moments the dynamic correlation function can be obtained by the maximum
entropy method. We apply this method to one-dimensional spinless fermion
system, which can be converted to the spin 1/2 Heisenberg model in a special
case. The dynamical density-density correlation function is obtained.Comment: 11 pages, latex, 4 figure