2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/217168We study a system in which the quantum dynamics of electrons depend on the particle density in their neighborhood. For any on-site repulsive interaction, we show that the exact two-body and three-body ground states are bound states. We also discuss the finite density case in a mean-field framework and we show that the system can undergo an unusual transition from an effective attractive interaction to a repulsive one, when varying the electron density.6 pages, 6 EPS figures, minor modifications and references addedStrongly Correlated Electronstext