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. 
Jihn E. Kim
hep-ph astro-ph.CO hep-ex