The Cosmic Neutrino Background and the Age of the Universe

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.

JCAP, in press

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• Detecting sterile neutrinos with KATRIN like experiments
• Probing the Effective Number of Neutrino Species with Cosmic Microwave Background
• Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies
• Anisotropies in the Cosmic Neutrino Background after WMAP 5-year Data
• On measuring the absolute scale of baryon acoustic oscillations
• A critical discussion on the $H_0$ tension
• The connection between cosmology and neutrino physics