2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/114589Here, it is found that dark energy and dark matter emerge from the gravitational sector, if non-linear term of scalar curvature is added to Einstein-Hilbert lagrangian. An equation of state for dark energy, having the form $p_{\rm de} = - ρ_{\rm de} + f(a) (with $p_{\rm de}(ρ_{\rm de})$ being the pressure(density) for dark energy, $f(a)$ being a function of scale feactor $a(t)$ and $t$ being the cosmic time) is explored. Interestingly, this equation of state leads to a phantom barrier ${\rm w}_{\rm de} = p_{\rm de}/ρ_{\rm de} = - 1$ at $a = a_{\rm w}$. It is found that when $a < a_{\rm w}, {\rm w}_{\rm de} > - 1$ and ${\rm w}_{\rm de} < - 1$ for $a > a_{\rm w},$ showing a transition from non-phantom to phantom phase at $a = a_{\rm w} < a_0 (a_0$ being current scale factor of the universe). PACS no.: 98.80 Cq.10 PAGES. To appear in Phys. Lett. BAstrophysicsGeneral Relativity and Quantum CosmologyHigh Energy Physics - Theorytext