2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/20988A self-energy-functional approach is applied to construct cluster approximations for correlated lattice models. It turns out that the cluster-perturbation theory (Senechal et al, PRL 84, 522 (2000)) and the cellular dynamical mean-field theory (Kotliar et al, PRL 87, 186401 (2001)) are limiting cases of a more general cluster method. Results for the one-dimensional Hubbard model are discussed with regard to boundary conditions, bath degrees of freedom and cluster size.4 pages, final version with minor changesStrongly Correlated ElectronsSuperconductivitytext