Power Spectrum

• P(k) today should look something like this (though be careful when combining data - the normalizations are not obvious). Note: 1) the turnover point indicative of the equality time, 2) large-scale (small k) fluctuations maintain their primordial shape (P(k) ∝ kn), 3) small-scale (large k) fluctuations have been processed as they successively entered the horizon

Garcia-Bellido (2002)

• Here is P(k) from the 2dF survey (Lahav et al. 2002) along with the best-fit cosmological model (see caption of image). As stated in the caption, the fit is computed in a range where linear theory holds. The 2dF power spectrum is the most current, and improves on previous surveys. The Sloan survey promises to improve yet again the measurement of P(k)

Lahav et al. and the 2dF Galaxy Redshift Survey Team (2002)

• Based on the fit to the 2dF power spectrum (and previous results) we are nailing down the cosmological parameters. The "concordance model" is a spatially flat, Λ-CDM universe (i.e. the nature of dark matter appears to be "cold"). Things are consistent with CMB and other data. Shown below is a comparison of cosmological parameters from the 2dF power spectrum results and published CMB results (n is primordial spectral index, Ω_b is baryonic matter density, Ω_c is CDM matter density, h is Hubble constant). Note the tight agreement between two completely different data sets. Further below is a comparison of cosmological parameters obtained from various sources such as LSS, CMB, supernovae measurements (SN) and data from HST

Garcia-Bellido (2002)

Garcia-Bellido (2002)

• Based on all these data sets, the cosmological parameters in the current concordance model are:
  Ω_m = (1-Ω_Λ) ≈ 0.3
  Ω_bh² ≈ 0.02
  h ≈ 0.7
  primordial spectrum index n ≈ 1
  
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