Dark energy, QCD axion, BICEP2, and trans-Planckian decay constant
  Discrete symmetries allowed in string compactification are the mother of all
global symmetries which are broken at some level. We discuss the resulting
pseudo-Goldstone bosons, in particular the QCD axion and a temporary
cosmological constant, and inflatons. We also comment on some implications of
the recent BICEP2 data.
