  We have studied the ground state of the two-dimensional Hubbard model by
using the adaptive sampling quantum monte carlo method. We found enhancement of
the d-wave correlation function, the spin gap and the coexistence of both the
commensurate and incommensurate peaks in $S(\vec{q})$, which does not
contradict a recent experimental finding that both the resonance peak and the
incommensurate peaks reside in the same doping level of YBCO and BSCCO.
