Are cosmological neutrinos free-streaming?

Abstract

Precision data from cosmology suggest neutrinos stream freely and hence interact very weakly around the epoch of recombination. We study this issue in a simple framework where neutrinos recouple instantaneously and stop streaming freely at a redshift z_i. The latest cosmological data imply z_i < 1500, the exact constraint depending somewhat on the assumed prior on z_i. This bound translates into a limit on the coupling strength between neutrinos and majoron-like particles phi, implying tau > 1 x 10^10 s (m_2/50 meV)^3 for the decay nu_2 -> nu_1+phi.

4 pages, 2 figures

References in corpus (6)

• Observational bounds on the cosmic radiation density
• Constraint on the Effective Number of Neutrino Species from the WMAP and SDSS LRG Power Spectra
• Cosmological neutrino mass detection: The best probe of neutrino lifetime
• Nonlinear corrections to the cosmological matter power spectrum and scale-dependent galaxy bias: implications for parameter estimation
• Anisotropies in the Cosmic Neutrino Background after WMAP 5-year Data
• Conservative Estimates of the Mass of the Neutrino from Cosmology