  Multi-band quasi-particle calculations based on perturbation theory and
dynamical mean field methods show that the creation of a photoemission hole
state in Sr$_2$RuO$_4$ is associated with a highly anisotropic self-energy.
Since the narrow Ru-derived $d_{xz,yz}$ bands are more strongly distorted by
Coulomb correlations than the wide $d_{xy}$ band, charge is partially
transferred from $d_{xz,yz}$ to $d_{xy}$, thereby shifting the $d_{xy}$ van
Hove singularity close to the Fermi level.
