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Cosmology of neutrinos and extra light particles after WMAP3

Marco Cirelli·Alessandro Strumia
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Abstract

We study how present data probe standard and non-standard properties of neutrinos and the possible existence of new light particles, freely-streaming or interacting, among themselves or with neutrinos. Our results include: sum m_nu < 0.40 eV at 99.9% C.L.; that extra massless particles have abundance Delta N_nu = 2 pm 1 if freely-streaming and Delta N_nu = 0 pm 1.3 if interacting; that 3 interacting neutrinos are disfavored at about 4 sigma. We investigate the robustness of our results by fitting to different sub-sets of data. We developed our own cosmological computational tools, somewhat different from the standard ones.

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Marco Cirelli, Alessandro Strumia. 2006-12-07. Cosmology of neutrinos and extra light particles after WMAP3. https://doi.org/10.1088/1475-7516%2F2006%2F12%2F013

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