Tracking quintessence would require two cosmic coincidences

Good tracking requires that the quintessence energy fraction slowly increase while the roll λ ≡ -d ln V/ anti κdφ slowly decreases, but is not yet truly slow-rolling. The supernova bound on the present quintessence equation of state requires either (1) a cosmological constant or other fine-tuned ''crawling quintessence'' or (2) ''roll-over quintessence'' that tracked until recently, but now became slow rolling, because of a sharp increase in potential curvature. Thus, fine-tuning is required by constant equation of state and inverse power potentials, but can be avoided by the SUGRA and Skordis-Albrecht potentials and other good trackers, provided quintessence energy domination and slow roll both began only recently. This makes the time in which we live special in two respects. (orig.)