Universal Lepton Asymmetry: New Constraints from the Cosmic Microwave   Background and Primordial Nucleosynthesis
  We study the primordial nucleosynthesis and cosmic age in the presence of a net lepton asymmetry as well as baryon asymmetry. We explore a previously unnoted region of the parameter space in which very large baryon densities $0.1 \le \Omega_b \le 1$ can be accommodated within the light-element constraints from primordial nucleosynthesis. This parameter space consists of $\nu_\mu$ and $\nu_\tau$ degeneracies with a small $\nu_e$ degeneracy. Constraints from cosmic microwave background fluctuations are also discussed (orito00). 
T. Kajino, M. Orito, G. J. Mathews, and R. N. Boyd