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 $\mathrm{\Lambda }$. 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 $\mathrm{\Lambda }$ models: compatibility with the spatial flatness predicted 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, ${\mathrm{\Omega }}_{m0}\sim 0.2$, and a higher age, $H_0{t}_0\gtrsim 1$. 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.