Resurrection of large lepton number asymmetries from neutrino flavor   oscillations
  We numerically solve the evolution equations of neutrino three-flavor density matrices, and show that, even if neutrino oscillations mix neutrino flavors, large lepton number asymmetries are still allowed in certain limits by Big Bang Nucleosynthesis (BBN). 
Gabriela Barenboim, William H. Kinney, Wan-Il Park
hep-ph astro-ph.CO