An alternative to the cosmological 'concordance model'
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 po...
| Main Authors: | , , , |
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| Format: | Journal article |
| Language: | English |
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2003
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| _version_ | 1797064469497511936 |
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| author | Blanchard, A Douspis, M Rowan-Robinson, M Sarkar, S |
| author_facet | Blanchard, A Douspis, M Rowan-Robinson, M Sarkar, S |
| author_sort | Blanchard, A |
| collection | OXFORD |
| description | 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 {\em 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 problem is that the Hubble constant is required to be rather low: $H_0 \simeq 46$ km/s/Mpc; 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 ($\Omega_X \sim 0.1$) of matter which does not cluster on small scales, e.g. relic neutrinos with mass of order eV or a `quintessence' with $w \sim 0$, 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 {\em direct} evidence for a non-zero cosmological constant. |
| first_indexed | 2024-03-06T21:14:46Z |
| format | Journal article |
| id | oxford-uuid:3f66240c-1cf7-423e-89d5-b94cae4a5ce6 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T21:14:46Z |
| publishDate | 2003 |
| record_format | dspace |
| spelling | oxford-uuid:3f66240c-1cf7-423e-89d5-b94cae4a5ce62022-03-26T14:31:46ZAn alternative to the cosmological 'concordance model'Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:3f66240c-1cf7-423e-89d5-b94cae4a5ce6EnglishSymplectic Elements at Oxford2003Blanchard, ADouspis, MRowan-Robinson, MSarkar, SPrecision 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 {\em 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 problem is that the Hubble constant is required to be rather low: $H_0 \simeq 46$ km/s/Mpc; 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 ($\Omega_X \sim 0.1$) of matter which does not cluster on small scales, e.g. relic neutrinos with mass of order eV or a `quintessence' with $w \sim 0$, 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 {\em direct} evidence for a non-zero cosmological constant. |
| spellingShingle | Blanchard, A Douspis, M Rowan-Robinson, M Sarkar, S An alternative to the cosmological 'concordance model' |
| title | An alternative to the cosmological 'concordance model' |
| title_full | An alternative to the cosmological 'concordance model' |
| title_fullStr | An alternative to the cosmological 'concordance model' |
| title_full_unstemmed | An alternative to the cosmological 'concordance model' |
| title_short | An alternative to the cosmological 'concordance model' |
| title_sort | alternative to the cosmological concordance model |
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