title: Dark energy: recent observations and future prospects.
abstract: Dark energy presents us with a challenging puzzle: understanding the new physics seen in the acceleration of the expansion of the Universe. Measurements using type-Ia supernovae (SNe) first detected this acceleration, and this approach remains the most direct route to studying the details of the Universe's expansion history that can teach us more about the nature of the dark energy. Such measurements are, however, extremely demanding in both precision and accuracy, since the different dark-energy models predict very small differences in the expansion history. While several cosmological probes may reach the required statistical uncertainties, the key measurement limit will be the systematic uncertainty. The supernova-measurement approach has the advantage of well-studied systematic uncertainties, allowing a next-generation experiment to be pursued. We briefly review the progress to date and examine the promise of future surveys with large numbers of SNe and well-bounded systematics.
authors.affiliation: Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
authors.forename: Saul
authors.initials: S
authors.lastname: Perlmutter