An alternative to the cosmological "concordance model"

作者：Blanchard A^*; Douspis M; Rowan Robinson M; Sarkar S

来源：Astronomy & Astrophysics, 2003, 412(1): 35-44.

DOI：10.1051/0004-6361:20031425

• cosmology : theory
• cosmology : cosmic microwave background
• cosmology : large scale structure of Universe
• cosmology : cosmological parameters

Precision measurements of the cosmic microwave background by WMAP are believed to have established a flat Lambda-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 Lambda-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 similar or equal to 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 (Omega(X) similar to 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 similar to 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-alpha 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.

• 出版日期2003-12