Structure formation and the time dependence of quintessence

We discuss the influence of dark energy on structure formation, especially the effects on sigma (8). Our interest is particularly focused on quintessence models with a time-dependent equation of state and non-negligible quintessence component in the early universe. We obtain an analytic expression for sigma (8) valid for a large class of dark energy models. We conclude that structure formation is a good indicator for the history of dark energy and use our results to set constraints on quintessence models.