Constraints from high redshift supernovae upon scalar field cosmologies

Recent observations of high-redshift type Ia supernovae have placed stringent constraints on the cosmological constant {Λ}. We explore the implications of these SNe observations for cosmological models in which a classically evolving scalar field currently dominates the energy density of the Universe. Such models have been shown to share the advantages of {Λ} models: compatibility with the spatial flatness predicted by inflation; a Universe older than the standard Einstein--de Sitter model; and, combined with cold dark matter, predictions for large-scale structure formation in good agreement with data from galaxy surveys. Compared to the cosmological constant, these scalar field models are consistent with the SNe observations for a lower matter density, Ωₘ₀~0.2, and a higher age, H₀t₀1. Combined with the fact that scalar field models imprint a distinctive signature on the cosmic microwave background anisotropy, they remain currently viable and should be testable in the near future.