Cosmological perturbations of axion with a dynamical decay constant

Takeshi Kobayashi, Fuminobu Takahashi

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1 Citation (Scopus)


A QCD axion with a time-dependent decay constant has been known to be able to accommodate high-scale inflation without producing topological defects or too large isocurvature perturbations on CMB scales. We point out that a dynamical decay constant also has the effect of enhancing the small-scale axion isocurvature perturbations. The enhanced axion perturbations can even exceed the periodicity of the axion potential, and thus lead to the formation of axionic domain walls. Unlike the well-studied axionic walls, the walls produced from the enhanced perturbations are not bounded by cosmic strings, and thus would overclose the universe independently of the number of degenerate vacua along the axion potential.

Original languageEnglish
Article number056
JournalJournal of Cosmology and Astroparticle Physics
Issue number8
Publication statusPublished - 2016 Aug 25


  • axions, Cosmic strings
  • cosmological perturbation theory
  • domain walls
  • monopoles
  • physics of the early universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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