The consensus of opinion in cosmology is that the Universe is currently undergoing a period of accelerated expansion. With current and proposed high precision experiments it offers the hope of being able to discriminate between the two competing models that are being suggested to explain the observations, namely a cosmological constant or a time dependent “quintessence” model. The latter suffers from a plethora of scalar field potentials all leading to similar late time behavior of the universe and, hence, to a lack of predictability. In this paper, we develop a model independent approach which simply involves parametrizing the dark energy equation of state in terms of known observables. This allows us to analyze the impact dark energy has had on cosmology without the need to refer to particular scalar field models and opens up the possibility that future experiments will be able to constrain the dark energy equation of state in a model independent manner.

• Received 22 August 2002

DOI:https://doi.org/10.1103/PhysRevD.67.063521