Non-invertible Symmetries in Weyl Fermions, and Applications to Fermion-Boundary Scattering Problem
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| Format: | Preprint |
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2026
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| author | Wei, Pengcheng Zheng, Yunqin |
| author_facet | Wei, Pengcheng Zheng, Yunqin |
| contents | We construct a family of non-invertible topological defects in two-dimensional theories of $n$ Weyl fermions. The construction relies on the existence of $G$-symmetric conformal boundary conditions for $n$ Dirac fermions. Upon unfolding, these boundary conditions become topological defects $\mathcal D$ of $n$ Weyl fermions that intertwine the two $G$-representations, and they are generically non-invertible. For $G=U(1)^n$, we show that $\mathcal D$ is a duality defect associated with gauging a finite Abelian group $Γ$, and we give an explicit algorithm for determining $Γ$ and its action on the fermions. We also show that the same finite-Abelian gauging description applies in certain restricted examples with non-Abelian $G$. By contrast, for certain non-Abelian symmetry structures, including the $G=SU(2)$ symmetry appearing in the $1$-$5$-$7$-$8$-$9$ problem, we prove that $\mathcal D$ cannot be realized as a duality defect for gauging any finite Abelian group. Finally, we explain how the duality-defect perspective gives a streamlined derivation of fermion scattering from a conformal boundary. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_19363 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Non-invertible Symmetries in Weyl Fermions, and Applications to Fermion-Boundary Scattering Problem Wei, Pengcheng Zheng, Yunqin High Energy Physics - Theory Strongly Correlated Electrons We construct a family of non-invertible topological defects in two-dimensional theories of $n$ Weyl fermions. The construction relies on the existence of $G$-symmetric conformal boundary conditions for $n$ Dirac fermions. Upon unfolding, these boundary conditions become topological defects $\mathcal D$ of $n$ Weyl fermions that intertwine the two $G$-representations, and they are generically non-invertible. For $G=U(1)^n$, we show that $\mathcal D$ is a duality defect associated with gauging a finite Abelian group $Γ$, and we give an explicit algorithm for determining $Γ$ and its action on the fermions. We also show that the same finite-Abelian gauging description applies in certain restricted examples with non-Abelian $G$. By contrast, for certain non-Abelian symmetry structures, including the $G=SU(2)$ symmetry appearing in the $1$-$5$-$7$-$8$-$9$ problem, we prove that $\mathcal D$ cannot be realized as a duality defect for gauging any finite Abelian group. Finally, we explain how the duality-defect perspective gives a streamlined derivation of fermion scattering from a conformal boundary. |
| title | Non-invertible Symmetries in Weyl Fermions, and Applications to Fermion-Boundary Scattering Problem |
| topic | High Energy Physics - Theory Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2605.19363 |