  We characterize the three-orbital Hubbard model using state-of-the-art
determinant quantum Monte Carlo (DQMC) simulations with parameters relevant to
the cuprate high-temperature superconductors. The simulations find that doped
holes preferentially reside on oxygen orbitals and that the ({\pi},{\pi})
antiferromagnetic ordering vector dominates in the vicinity of the undoped
system, as known from experiments. The orbitally-resolved spectral functions
agree well with photoemission spectroscopy studies and enable identification of
orbital content in the bands. A comparison of DQMC results with exact
diagonalization and cluster perturbation theory studies elucidates how these
different numerical techniques complement one another to produce a more
complete understanding of the model and the cuprates. Interestingly, our DQMC
simulations predict a charge-transfer gap that is significantly smaller than
the direct (optical) gap measured in experiment. Most likely, it corresponds to
the indirect gap that has recently been suggested to be on the order of 0.8 eV,
and demonstrates the subtlety in identifying charge gaps.
