  Studying the antiferromagnetic phase of the Hubbard model by dynamical mean
field theory, we observe striking differences with static (Hartree-Fock) mean
field: The Slater band is strongly renormalized and spectral weight is
transferred to spin-polaron side bands. Already for intermediate values of the
interaction $U$ the overall bandwidth is larger than in Hartree-Fock, and the
gap is considerably smaller. Such differences survive any renormalization of
$U$. Our photoemission experiments for Cr-doped V$_2$O$_3$ show spectra
qualitatively well described by dynamical mean field theory.
