2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/9478A new single-dynamical-scalar-field model of dark energy is proposed, in which either higher derivative terms nor structures of extra dimension are needed. With the help of a fixed background vector field, the parameter for the effective equation of state of dark energy may cross $w=-1$ in the evolution of the universe. After suitable choice of the potential, the crossing $w=-1$ and transition from decelerating to accelerating occur at $z\approx 0.2$ and $z\approx 1.7$, respectively.7 pages, 4 figuresAstrophysicstext