2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/188036The four-dimensional Friedman flat universe, filled with an ideal fluid with a linear (oscillating) inhomogeneous equation of state (EoS) depending on time, is studied. The equations of motion are solved. It is shown that in some cases there appears a quasi-periodic universe, which repeats the cycles of phantom-type space acceleration. The appearance of future singularities resulting from various choices for the input parameters is discussed.9 pages pdf, 4 figures. To appear in European Physical Journal CGeneral Relativity and Quantum Cosmologytext