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Dark radiation and inflationary freedom after Planck 2015
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Università di Roma “La Sapienza”, Italy.
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Number of Authors: 5
2016 (English)In: Physical Review D, ISSN 2470-0010, Vol. 93, no 8, 083523Article in journal (Refereed) Published
Abstract [en]

The simplest inflationary models predict a primordial power spectrum (PPS) of the curvature fluctuations that can be described by a power-law function that is nearly scale invariant. It has been shown, however, that the low-multipole spectrum of the cosmic microwave background anisotropies may hint at the presence of some features in the shape of the scalar PPS, which could deviate from its canonical power-law form. We study the possible degeneracies of this nonstandard PPS with the active neutrino masses, the effective number of relativistic species, and a sterile neutrino or a thermal axion mass. The limits on these additional parameters are less constraining in a model with a nonstandard PPS when including only the temperature autocorrelation spectrum measurements in the data analyses. The inclusion of the polarization spectra noticeably helps in reducing the degeneracies, leading to results that typically show no deviation from the Lambda CDM model with a standard power-law PPS. These findings are robust against changes in the function describing the noncanonical PPS. Albeit current cosmological measurements seem to prefer the simple power-law PPS description, the statistical significance to rule out other possible parametrizations is still very poor. Future cosmological measurements are crucial to improve the present PPS uncertainties.

Place, publisher, year, edition, pages
2016. Vol. 93, no 8, 083523
National Category
Physical Sciences
URN: urn:nbn:se:su:diva-130863DOI: 10.1103/PhysRevD.93.083523ISI: 000374960700001OAI: diva2:934126
Available from: 2016-06-08 Created: 2016-06-07 Last updated: 2016-06-08Bibliographically approved

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Gerbino, Martina
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Department of PhysicsThe Oskar Klein Centre for Cosmo Particle Physics (OKC)Nordic Institute for Theoretical Physics (Nordita)
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