Density-matrix renormalization-group method in momentum space.

A momentum-space approach of the density-matrix renormalization-group ~DMRG! method is developed. Ground-state energies of the Hubbard model are evaluated using this method and compared with exact diagonalization as well as quantum Monte Carlo results. It is shown that the momentum-space DMRG is a very useful numerical tool for studying the Hubbard model and other fundamental models of interacting electrons in two dimensions. For the Hubbard model in two dimensions, the momentum-space DMRG method reproduces accurately the exact diagonalization results of ground-state energies on a 434 lattice and yields new upper bounds of ground-state energies on an 838 lattice. @S0163-1829~96!52416-1#