2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/115890Regionally averaged relativistic cosmologies have recently been considered as a possible explanation for the apparent late time acceleration of the Universe. This contribution reports on a mean field description of the backreaction in terms of a minimally coupled regionally homogeneous scalar field evolving in a potential, then giving a physical origin to the various phenomenological scalar fields generically called quintessence fields. As an example, the correspondence is then applied to scaling solutions.To appear in the Proceedings of the SF2A conference, June 2006. One reference correctedAstrophysicsGeneral Relativity and Quantum Cosmologytext