Features in the primordial power spectrum: constraints from the CMB and the limitation of the 2dF and SDSS redshift surveys to detect them

We allow a more general (step-function) form of the primordial power spectrum than the usual featureless power-law Harrison–Zeldovich (with spectral index n = 1) power spectrum, and fit it to the latest Cosmic Microwave Background data sets. Although the best-fitting initial power spectrum can differ significantly from the powerlaw shape, and contains a dip at scales k ∼ 0.003 hMpc, we find that Ωm ≈ 0.24, consistent with previous analyses that assume power-law initial fluctuations. We also explore the feasibility of the early releases of the 2dF and SDSS galaxy redshifts surveys to see these features, and we find that even if features exist in the primordial power spectrum, they are washed out by the window functions of the redshift surveys on scales k < 0.03 hMpc.