Axion strings are superconducting

Hajime Fukuda*, Aneesh V. Manohar, Hitoshi Murayama, Ofri Telem

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


We explore the cosmological consequences of the superconductivity of QCD axion strings. Axion strings can support a sizeable chiral electric current and charge density, which alters their early universe dynamics. We examine the possibility that shrinking axion string loops can become effectively stable remnants called vortons, supported by the repulsive electromagnetic force of the string current. We find that vortons in our scenario are generically unstable, and so do not pose a cosmological difficulty. Furthermore, if a primordial magnetic field (PMF) exists in the early universe, a large current is induced on axion strings, creating a significant drag force from interactions with the surrounding plasma. As a result, the strings are slowed down, which leads to an orders of magnitude enhancement in the number of strings per Hubble volume. Finally, we study potential implications for the QCD axion relic abundance. The QCD axion window is shifted by orders of magnitude in some parts of our parameter space.

Original languageAmerican English
Article number52
JournalJournal of High Energy Physics
Issue number6
StatePublished - Jun 2021
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2021, The Author(s).


  • Beyond Standard Model
  • Solitons Monopoles and Instantons


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