2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/34244Assuming a flat Friedmann-Robertson-Walker cosmology with a single perfect fluid, we propose a pressure-density ratio that evolves as a specific universal function of the scale parameter. We show that such a ratio can indeed be consistent with several observational constraints including those pertaining to late-time accelerated expansion. Generic dynamical scalar field models of Dark energy (with quadratic kinetic terms in their Lagrange density) are shown to be in accord with the proposed equation-of-state ratio, provided the current matter density parameter $Ω_{m0} < 0.23$ - a value {\it not} in agreement with recent measurements.5 pages Revtex, 2 eps figures, a reference and a comment addedGeneral Relativity and Quantum CosmologyAstrophysicsHigh Energy Physics - Theorytext