Cosmology of neutrinos and extra light particles after WMAP3

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.

18 pages, 8 figures. Added in v2: an explicit comparison of our code with CAMB, some clarifications on the statistical analysis and some references. Matches version published in JCAP

References in corpus (2)

• Can sterile neutrinos be ruled out as warm dark matter candidates?
• Polarization Observations with the Cosmic Background Imager

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