Constraints on Dark Energy from Supernovae, Gamma‐Ray Bursts, Acoustic Oscillations, Nucleosynthesis, Large‐Scale Structure, and the Hubble Constant

The luminosity distance versus redshift law is now measured using supernovae and γ-ray bursts, and the angular size distance is measured at the surface of last scattering by the CMB and at z = 0.35 by baryon acoustic oscillations. In this paper, this data is fit to models for the equation of state with w = -1, w = constant, and w ( z ) = w 0 + w a (1 - a ). The last model is poorly constrained by the distance data, leading to unphysical solutions where the dark energy dominates at early times unless the large-scale structure and acoustic scale constraints are modified to allow for early-time dark energy effects. A flat ΛCDM model is consistent with all the data.