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Unpaired Weyl fermion on an axion string in a finite lattice

Jonathan D. Kroth* and Srimoyee Sen†

  • *Contact author: jdkroth@iastate.edu
  • †Contact author: srimoyee08@gmail.com
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Phys. Rev. D 112, 034510 – Published 26 August, 2025

DOI: https://doi.org/10.1103/twkg-8p31

Abstract

Domain wall fermions use a 2n-dimensional spacetime defect embedded in (2n+1)-dimensional spacetime to realize massless lattice Dirac fermions. Recent work has extended this idea to realize a single unpaired Weyl fermion in a finite lattice. Here, we realize the same using a 2n-dimensional string defect embedded in (2n+2)-dimensional spacetime on a finite lattice for n=1. This string is a lattice version of the continuum axion string described in Callan-Harvey [Nucl. Phys. B250, 427 (1985)]. Our results are obtained in a Hamiltonian formulation in Minkowski spacetime. Extending the results to Euclidean spacetime and to n>1 is straightforward. This work has applications to lattice chiral gauge theories and axion cosmology.

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Phys. Rev. D 112, 034510– Published 26 August, 2025
  • Received 16 June 2025
  • Accepted 8 August 2025
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