2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/184779We demonstrate that a suitable coupling between a quintessence scalar field and a pressureless cold dark matter (CDM) fluid leads to a constant ratio of the energy densities of both components which is compatible with an accelerated expansion of the Universe.12 pages, LaTeX; new material on the stability analysis and on the interaction potential added, reference list enlarged and updated; to be published in PLBAstrophysicsGeneral Relativity and Quantum CosmologyHigh Energy Physics - Phenomenologytext