The Cosmic Neutrino Background and the Age of the Universe
Francesco de Bernardis (Rome), Alessandro Melchiorri (Rome), Licia, Verde (ICE & Princeton), Raul Jimenez (ICE & Princeton)
TL;DR
This paper uses cosmological data, including Hubble parameter measurements, to tightly constrain the effective number of relativistic particles, confirming a neutrino background with high significance and refining the universe's age estimates.
Contribution
It provides the most stringent constraints on N_eff using recent H(z) data and confirms the neutrino background with high confidence.
Findings
N_eff=3.7 (-1.2) (+1.1) at 95% CL
Neutrino background detected with >99% confidence
Universe's age constraints improved by a factor of 3
Abstract
We discuss the cosmological degeneracy between the age of the Universe, the Hubble parameter and the effective number of relativistic particles N_eff. We show that independent determinations of the Hubble parameter H(z) as those recently provided by Simon,Verde, Jimenez (2006), combined with other cosmological data sets can provide the most stringent constraint on N_eff, yielding N_eff=3.7 (-1.2) (+1.1) at 95% confidence level. A neutrino background is detected with high significance: N_eff >1.8 at better than 99% confidence level. Constraints on the age of the universe in the framework of an extra background of relativistic particles are improved by a factor 3.
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