Physics Letters B (Nov 2015)

Cosmologically safe QCD axion as a present from extra dimension

  • Masahiro Kawasaki,
  • Masaki Yamada,
  • Tsutomu T. Yanagida

DOI
https://doi.org/10.1016/j.physletb.2015.08.043
Journal volume & issue
Vol. 750, no. C
pp. 12 – 16

Abstract

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We propose a QCD axion model where the origin of PQ symmetry and suppression of axion isocurvature perturbations are explained by introducing an extra dimension. Each extra quark–antiquark pair lives on branes separately to suppress PQ breaking operators. The size of the extra dimension changes after inflation due to an interaction between inflaton and a bulk scalar field, which implies that the PQ symmetry can be drastically broken during inflation to suppress undesirable axion isocurvature fluctuations.