An alternative to the cosmological “concordance model”

Abstract

Abstract. Precision measurements of the cosmic microwave background by WMAP are believed to have established a flat Λ-dominated universe, seeded by nearly scale-invariant adiabatic primordial fluctuations. However by relaxing the hypothesis that the fluctuation spectrum can be described by a single power law, we demonstrate that an Einstein-de Sitter universe with zero cosmological constant can fit the data as well as the best concordance model. Moreover unlike a Λ-dominated universe, such an universe has no strong integrated Sachs-Wolfe effect, so is in better agreement with the low quadrupole seen by WMAP. The main concern is that the Hubble constant is required to be rather low: H 0 46 km s −1 Mpc −1 ; we discuss whether this can be consistent with observations. Furthermore for universes consisting only of baryons and cold dark matter, the amplitude of matter fluctuations on cluster scales is too high, a problem which seems generic. However, an additional small contribution (Ω X ∼ 0.1) of matter which does not cluster on small scales, e.g. relic neutrinos with mass of order eV or a "quintessence" with w ∼ 0, can alleviate this problem. Such models provide a satisfying description of the power spectrum derived from the 2dF galaxy redshift survey and from observations of the Ly-α forest. We conclude that Einstein-de Sitter models can indeed accommodate all data on the large scale structure of the Universe, hence the Hubble diagram of distant type Ia supernovae remains the only direct evidence for a non-zero cosmological constant.

Is the Velocity Interpretation of the Redshift of Spectral Lines in Accordance with Astronomical Data?

“…show not only a better agreement with the expansion tests but, in addition, they perfectly fit the BAO power spectrum and as pointed out by Blanchard et al [6] have no strong integrated Sachs-Wolfe effect and are in better agreement with the low quadrupole seen by WMAP.…”

Constraints on intergalactic dust from quasar colours

“…However, in Ref. [8] it was demonstrated how the recent CMB anisotropy observations can be explained also by an Einstein-de Sitter cosmology with no dark energy if one allows for a low Hubble parameter, H 0 50 km/s/Mpc, the value currently favoured by gravitational lensing time delay measurements [9]. It is further argued that conflict with large scale structure measurements can be avoided by suppressing cluster scale mass fluctuations assuming a small but non-negligible hot dark matter component.…”

Are domain walls ruled out?

“…[19]). In particular, analyses of the recent measurements of the temperature-luminosity relation of distant clusters observed with XMM-Newton and Chandra satellites, seem to be consistent with higher values of Ω m ∼ 0.8 ( [24]).…”