  The competition between commensurate and incommensurate spin-density-wave
phases in the infinite-dimensional single-band Hubbard model is examined with
quantum Monte Carlo simulation and strong and weak coupling approximations.
Quantum fluctuations modify the weak-coupling phase diagram by factors of order
unity and produce remarkable agreement with the quantum Monte Carlo data, but
strong-coupling theories (that map onto effective Falicov-Kimball models)
display pathological behavior. The single-band model can be used to describe
much of the experimental data in Cr and its dilute alloys with V and Mn.
