Lepton Asymmetric Universe
  The recent observation of $^4$He implies that our universe has a large lepton
asymmetry. We consider the Affleck-Dine (AD) mechanism for lepton number
generation. In the AD mechanism, non-topological solitons called L-balls are
produced, and the generated lepton number is confined in them. The L-balls
protect the generated lepton number from being converted to baryon number
through the sphaleron processes. We study the formation and evolution of the
L-balls and find that the universe with large lepton asymmetry suggested by the
recent $^4$He measurement can be realized.
