New scenario of QCD axion clump formation. Part I. Linear analysis

Naoya Kitajima, Kazuhiro Kogai, Yuko Urakawa

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


The QCD axion acquires the potential through the non-perturbative effect of the QCD matters around the QCD phase transition. During this period, the direct interaction between the axion and the QCD matters sets in. Focusing on the impact of this direct interaction, we propose two scenarios where the fluctuation of the axion can rapidly grow, potentially leading to the formation of axion miniclusters even if the Peccei-Quinn (PQ) symmetry was already broken during inflation. The first scenario assumes that the primordial curvature perturbation at the horizon scale during the QCD epoch was significantly enhanced and the second one assumes that the initial misalignment was tuned around the hilltop of the potential.

Original languageEnglish
Article number039
JournalJournal of Cosmology and Astroparticle Physics
Issue number3
Publication statusPublished - 2022 Mar 1


  • axions
  • physics of the early universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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