Sterile neutrinos, lepton asymmetries, primordial elements: how much of each?

Abstract

We investigate quantitatively the extent to which having a primordial leptonic asymmetry (n_nu \neq n_nubar) relaxes the bounds on light sterile neutrinos imposed by BBN and LSS. We adopt a few assumptions that allow us to solve the neutrino evolution equations over a broad range of mixing parameters and asymmetries. For the general cases of sterile mixing with the electron or muon neutrino, we identify the regions that can be reopened. For the particular case of a LSND-like sterile neutrino, soon to be rejected or confirmed by MiniBooNE, we find that an asymmetry of the order of 10^-4 is needed to lift the conflicts with cosmology.

18 pages, 2 figures. v2: References and minor comments added. Matches version published on PRD

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• Multi-momentum and multi-flavour active-sterile neutrino oscillations in the early universe: role of neutrino asymmetries and effects on nucleosynthesis
• Unveiling secret interactions among sterile neutrinos with big-bang nucleosynthesis
• Revisiting cosmological bounds on radiative neutrino lifetime
• Primordial lepton asymmetries in the precision cosmology era: Current status and future sensitivities from BBN and the CMB
• MiniBooNE Results and Neutrino Schemes with 2 sterile Neutrinos: Possible Mass Orderings and Observables related to Neutrino Masses
• Minimal dark energy: key to sterile neutrino and Hubble constant tensions?
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• WMAP 5-year constraints on lepton asymmetry and radiation energy density: Implications for Planck
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• Constraints on primordial lepton asymmetries with full neutrino transport
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• Constraints on new physics around the MeV scale with cosmological observations
• Light sterile neutrinos from a late phase transition
• Testing Primordial Abundances With Sterile Neutrinos
• Return of the Lepton Number: Sterile Neutrino Dark Matter Production and the Revival of the Shi-Fuller Mechanism
• Exploring Ultralight Scalar Assistance in Sterile Neutrino Dark Matter: Cold Spectrum and Unusual X/Gamma-ray Signatures
• The effect of primordial fluctuations on neutrino oscillations
• Challenge to Anomalous Phenomena in Solar Neutrino