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More on 8D nonsupersymmetric branes and heterotic strings

Yuta Hamada1,2,*, Arata Ishige2,†, and Yuichi Koga3,‡

  • *Contact author: yhamada@post.kek.jp
  • †Contact author: arata@post.kek.jp
  • ‡Contact author: koga.yuichi@phys.kyushu-u.ac.jp
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Phys. Rev. D 113, 046012 – Published 17 February, 2026

DOI: https://doi.org/10.1103/yb7p-425g

Abstract

We determine the maximal gauge groups arising in E8 heterotic string theory on T2. Our analysis proceeds along two approaches. First, we start the moduli space of the supersymmetric heterotic string theory on T2 focusing on points of maximal gauge enhancement. At these special points, the charge lattice can exhibit a Z2 outer automorphism corresponding to the bulk gauge symmetry. By orbifolding the worldsheet theory by it with the fermion parity, we obtain the maximal gauge group of the E8 theory. Second, we directly study the toroidal compactification of 10D E8 heterotic string. Both approaches agree, yielding a classification of 22 maximal gauge groups. For each case, we present the corresponding massless spectrum. In light of the no global symmetry/cobordism conjecture in quantum gravity, our result also offers a classification of nonsupersymmetric branes in 8D supersymmetric heterotic string theories.

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Phys. Rev. D 113, 046012– Published 17 February, 2026
  • Received 12 November 2025
  • Accepted 20 January 2026
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