2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/29857A new theoretical analysis of the current-charge and charge-charge propagators is presented for the Hubbard model, using the static approximation for the Composite Operator Method. This approximation manifestly preserves a sum rule which governs the single-site dynamics. We compare our results with those obtained by numerical analysis.14 pages, 3 EPS figures, RevTeX, to be published in Physics Letters AStrongly Correlated Electronstext