The Cosmological Constant $Λ$, the Age of the Universe and Dark Matter: Clues from the Ly$α$-Forest

Abstract

Evidence for a positive cosmological constant $Λ$, derived from the Ly$α$-forest in high-resolution spectra of quasars, leads to a closed, low-density, $Λ$-dominated universe. The analysis is based on the assumption of a universal shell structure expanding predominantly with the Hubble flow. Supporting evidence comes from two pairs of very wide absorption lines in the spectra of two quasars separated by 8 arcmin on the sky. These results contradict the higher values of the density parameter $Ω_{M,0}$ derived, for example, from clusters of galaxies by the pure gravitational instability theory. Implications thereof and for the amount of non-baryonic dark matter in the universe are discussed with some $Λ$-dominated models, in particular with $Ω_{M,0} = 0.2$ and with pure baryonic models. The evidence points to low-density, closed models with spherical metric, expanding forever.