Constraining evolution of quintessence with CMB and SNIa data

The equation of state of the hypothetical dark energy component, which constitutes about two-thirds of the critical density of the Universe, may be very different from that of a cosmological constant. Employing a phenomenological model, we investigate semianalytically the constraints imposed on the scalar quintessence by supernovae observations, and by the acoustic scale extracted from recent cosmic microwave background data. We show that a universe with a quintessence-dominated phase in the dark age is consistent with the current observational constraints.