WMAP 5-year constraints on lepton asymmetry and radiation energy density: Implications for Planck

Abstract

In this paper we set bounds on the radiation content of the Universe and neutrino properties by using the WMAP-5 year CMB measurements complemented with most of the existing CMB and LSS data (WMAP5+All),imposing also self-consistent BBN constraints on the primordial helium abundance. We consider lepton asymmetric cosmological models parametrized by the neutrino degeneracy parameter and the variation of the relativistic degrees of freedom, due to possible other physical processes occurred between BBN and structure formation epochs. We find that WMAP5+All data provides strong bounds on helium mass fraction and neutrino degeneracy parameter that rivals the similar bounds obtained from the conservative analysis of the present data on helium abundance. We also find a strong correlation between the matter energy density and the redshift of matter-radiation equality, z_re, showing that we observe non-zero equivalent number of relativistic neutrinos mainly via the change of the of z_re, rather than via neutrino anisotropic stress claimed by the WMAP team. We forecast that the CMB temperature and polarization measurements observed with high angular resolutions and sensitivities by the future Planck satellite will reduce the errors on these parameters down to values fully consistent with the BBN bounds.

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Cited by in corpus (11)

• Primordial Nucleosynthesis: from precision cosmology to fundamental physics
• EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-Poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension
• Relic density of neutrinos with primordial asymmetries
• Cosmological lepton asymmetry with a nonzero mixing angle θ_{13}
• Detecting sterile neutrinos with KATRIN like experiments
• Improved constraints on lepton asymmetry from the cosmic microwave background
• Probing the Effective Number of Neutrino Species with Cosmic Microwave Background
• Lepton Asymmetric Universe
• Constraints on neutrino masses from WMAP5 and BBN in the lepton asymmetric universe
• Particle asymmetries in the early universe
• CP violation in bilinear R-parity violation and its consequences for the early universe