  A strong-coupling expansion for models of correlated electrons in any
dimension is presented. The method is applied to the Hubbard model in $d$
dimensions and compared with numerical results in $d=1$. Third order expansion
of the Green function suffices to exhibit both the Mott metal-insulator
transition and a low-temperature regime where antiferromagnetic correlations
are strong. It is predicted that some of the weak photoemission signals
observed in one-dimensional systems such as $SrCuO_2$ should become stronger as
temperature increases away from the spin-charge separated state.
