Journal Article

Primordial density perturbations with running spectral index: impact on non-linear cosmic structures

C. Fedeli, F. Finelli and L. Moscardini

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 407, issue 3, pages 1842-1858
Published in print September 2010 | ISSN: 0035-8711
Published online September 2010 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2010.17026.x
Primordial density perturbations with running spectral index: impact on non-linear cosmic structures

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We explore the statistical properties of non-linear cosmic structures in a flat Λ cold dark matter (ΛCDM) cosmology in which the index nS of the primordial power spectrum for scalar perturbations is allowed to depend on the scale. Within the inflationary paradigm, the running of the scalar spectral index can be related to the properties of the inflation potential, and it is hence of critical importance to test it with all kinds of observations, which cover the linear and non-linear regime of gravitational instability. We focus on the amount of running αS,0(≡ d nS/d ln (k/kp)) allowed by an updated combination of cosmic microwave background (CMB) anisotropy data and the 2dF Galaxy Redshift Survey. Our analysis constrains αS,0=− 0.051+0.047−0.053 (−0.034+0.039−0.040) at 95 per cent Confidence Level when (not) taking into account primordial gravitational waves in a ratio as predicted by canonical single field inflation, in agreement with other works. For the cosmological models best fitting the data both with and without running we studied the abundance of galaxy clusters and of rare objects, the halo bias, the concentration of dark matter haloes, the Baryon Acoustic Oscillation, the power spectrum of cosmic shear and the Integrated Sachs–Wolfe effect. We find that counting galaxy clusters in future X-ray and Sunyaev–Zel'dovich surveys could discriminate between the two models, more so if broad redshift information about the cluster samples will be available. Likewise, measurements of the power spectrum of cosmological weak lensing as performed by planned all-sky optical surveys such as EUCLID could detect a running of the primordial spectral index, provided the uncertainties about the source redshift distribution and the underlying matter power spectrum are well under control.

Keywords: galaxies: clusters: general; cosmological parameters; early Universe; large-scale structure of Universe

Journal Article.  12876 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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