Cosmological Parameters and the case for Cold Dark Matter

Abstract

Determinations of the main cosmological parameters are reviewed and the implications for cold dark matter discussed. There is no longer an age problem for an $Ω_o = 1, Λ= 0$ model and, if anything, there is now an age problem for low $Ω_o, Λ> 0$ models. Large scale structure and CMB fluctuation data are best fitted by a mixed dark matter $Ω_o$ = 1 universe. Difficulties for this model with cluster evolution, the baryon content of clusters, high z Lyman $α$ galaxies, and the evidence from Type Ia supernovae favouring low $Ω_o, Λ> 0$ models, are discussed critically.