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  • Open Access

Axion strings from string axions

James M. Cline*

Christos Litos† and Wei Xue‡

  • Institute for Fundamental Theory, Physics Department, University of Florida, Gainesville, Florida 32611, USA

  • *Contact author: jcline@physics.mcgill.ca
  • †Contact author: c.litos@ufl.edu
  • ‡Contact author: weixue@ufl.edu
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Phys. Rev. D 111, 123558 – Published 30 June, 2025

DOI: https://doi.org/10.1103/21zb-lzb9

Abstract

A favored scenario for axions to be dark matter is for them to form a cosmic string network that subsequently decays, allowing for a tight link between the axion mass and relic abundance. We discuss an example in which the axion is protected from quantum gravity effects that would spoil its ability to solve the strong CP problem: namely, a string theoretic axion arising from gauge symmetry in warped extra dimensions. Axion strings arise following the first-order Randall-Sundrum compactification phase transition forming at the junctions of three bubbles during percolation. Their tensions are at the low scale associated with the warp factor, and are parametrically smaller than the usual field-theory axion strings relative to the scale of their decay constant. Simulations of string network formation by this mechanism must be carried out to see whether the axion mass-relic density relation depends on the new parameters in the theory.

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Information

Phys. Rev. D 111, 123558– Published 30 June, 2025
  • Received 15 January 2025
  • Accepted 16 June 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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