Suppressing the lower multipoles in the CMB anisotropies

By C. Contaldi, Marco Peloso, Lev Kofman, A. Linde. 2003

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The Cosmic Microwave Background (CMB) anisotropy power on the largest angular scales observed both by WMAP and COBE DMR appears to be lower than the one predicted by the standard model of cosmology with almost scale free primordial perturbations arising from a period of inflation. One can either interpret this as a manifestation of cosmic variance or as a physical effect that requires an explanation. We discuss various mechanisms that could be responsible for the suppression of such low ℓ multipoles. Features in the late time evolution of metric fluctuations may do this via the integral Sachs–Wolfe effect. Another possibility is a suppression of power at large scales in the primordial spectrum induced by a fast rolling stage in the evolution of the inflaton field at the beginning of the last 65 e-folds of inflation. We illustrate this effect in a simple model of inflation and fit the resulting CMB spectrum to the observed temperature–temperature (TT) power spectrum. We find that the WMAP observations suggest a cutoff at kc = 4.9+1.3−1.6 × 10−4 Mpc−1 at 68% confidence, but only an upper limit of kc < 7.4 × 10−4 Mpc−1 at 95%. Thus, although it improves the fit of the data, the presence of a cutoff in power spectrum is only required at a level close to 2σ. This is obtained with a prior which corresponds to equal distribution w.r.t. kc. We discuss how other choices (such as an equal distribution w.r.t. lnkc, which is natural in the context of inflation) can affect the statistical interpretation.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/842b30ffa75303bda69fcaf5f159086c56805852

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Citations in the corpus

Planck intermediate results: LI. features in the cosmic microwave background temperature power spectrum and shifts in cosmological parameters (2016, neutral): “Despite interpretation of the deficit from different perspectives (e.g. Contaldi et al. 2003; Piao et al. 2004; Iqbal et al. 2015; Chen & Lin 2016; Cai et al. 2015a), up until now, its effect on the parameter shifts has not been thoroughly explored.”
Planck2018 results (2018, background): “where H((2)) n denotes the Hankel function of the second kind (Contaldi et al. 2003).”
An alternative to the cosmological 'concordance model' (2003, background): “This is arguably a simpler way to accomodate the observed low signal at l <∼ 20, than to invoke new physics (e.g. Spergel et al. 2003; Uzan, Kirchner & Ellis 2003a; Efstathiou 2003a, Contaldi et al. 2003, Cline, Crotty & Lesgourgues 2003).”
Punctuated inflation and the low CMB multipoles (2008, background): “fast roll) stage preceding slow roll inflation, driven by a quadratic potential has been considered earlier to provide a sharp drop in the scalar power spectrum at large scales [18, 30].”
Does the small CMB quadrupole moment suggest new physics (2003, methodology): “[13] found that the data favor having such a modified primordial spectrum at the 2σ level, whereas [12] obtain weaker evidence for a cutoff.”