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Singularity Selector: Topological Chirality via Non-Abelian Loops around Exceptional Points

Quantum Physics 2025-12-23 v1

Abstract

Chirality is more than a geometric curiosity; it governs measurable asymmetries across nature, from enantiomer-selective drugs and left-handed fermions in particle physics to handed charge transport in Weyl semimetals. We extend this universal concept to non-Hermitian systems by defining topological chirality, an invariant that emerges whenever an exceptional-points (EP) pair is present. Built from the non-commutative fundamental group and its braid representation, topological chirality acts as a singularity selector: clockwise EP loops occupy a homotopy class that avoids EPs, whereas counter-clockwise mirrors are equivalent only if they cross the EPs themselves. We confirm this binary rule in an optical microcavity and a non-Hermitian topological band. The same two-sheeted topology governs EP pairs in spin systems, photonic crystals and hybrid light-matter structures, where EP encirclements have already been demonstrated, so the framework transfers without alteration and confirms its experimental viability. Our findings lay the cornerstone for interpreting loop-sensitive observables such as spectral vorticity, the complex Berry phase and the non-Abelian holonomy. Finally, a gluing-of-planes construction extends the invariant to an n-sheeted surface hosting 2m EPs, unifying higher-order EP pairs.

Keywords

Cite

@article{arxiv.2512.18789,
  title  = {Singularity Selector: Topological Chirality via Non-Abelian Loops around Exceptional Points},
  author = {Kyu-Won Park and KyeongRo Kim and Kabgyun Jeong},
  journal= {arXiv preprint arXiv:2512.18789},
  year   = {2025}
}

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R2 v1 2026-07-01T08:35:38.275Z