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).