Spin-$s$ $Q$-systems: Twist and Open Boundaries

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Hauptverfasser: He, Yi-Jun, Hou, Jue, Liu, Yi-Chao, Tan, Zi-Xi
Format: Preprint
Veröffentlicht: 2025
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author He, Yi-Jun
Hou, Jue
Liu, Yi-Chao
Tan, Zi-Xi
author_facet He, Yi-Jun
Hou, Jue
Liu, Yi-Chao
Tan, Zi-Xi
contents In integrable spin chains, the spectral problem can be solved by the method of Bethe ansatz, which transforms the problem of diagonalization of the Hamiltonian into the problem of solving a set of algebraic equations named Bethe equations. In this work, we systematically investigate the spin-$s$ XXX chain with twisted and open boundary conditions using the rational $Q$-system, which is a powerful tool to solve Bethe equations. We establish basic frameworks of the rational $Q$-system and confirm its completeness numerically in both cases. For twisted boundaries, we investigate the polynomiality conditions of the rational $Q$-system and derive physical conditions for singular solutions of Bethe equations. For open boundaries, we uncover novel phenomena such as hidden symmetries and magnetic strings under specific boundary parameters. Hidden symmetries lead to the appearance of extra degeneracies in the Hilbert space, while the magnetic string is a novel type of exact string configuration, whose length depends on the boundary magnetic fields. These findings, supported by both analytical and numerical evidences, offer new insights into the interplay between symmetries and boundary conditions.
format Preprint
id arxiv_https___arxiv_org_abs_2502_15636
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Spin-$s$ $Q$-systems: Twist and Open Boundaries
He, Yi-Jun
Hou, Jue
Liu, Yi-Chao
Tan, Zi-Xi
High Energy Physics - Theory
Statistical Mechanics
Mathematical Physics
Exactly Solvable and Integrable Systems
In integrable spin chains, the spectral problem can be solved by the method of Bethe ansatz, which transforms the problem of diagonalization of the Hamiltonian into the problem of solving a set of algebraic equations named Bethe equations. In this work, we systematically investigate the spin-$s$ XXX chain with twisted and open boundary conditions using the rational $Q$-system, which is a powerful tool to solve Bethe equations. We establish basic frameworks of the rational $Q$-system and confirm its completeness numerically in both cases. For twisted boundaries, we investigate the polynomiality conditions of the rational $Q$-system and derive physical conditions for singular solutions of Bethe equations. For open boundaries, we uncover novel phenomena such as hidden symmetries and magnetic strings under specific boundary parameters. Hidden symmetries lead to the appearance of extra degeneracies in the Hilbert space, while the magnetic string is a novel type of exact string configuration, whose length depends on the boundary magnetic fields. These findings, supported by both analytical and numerical evidences, offer new insights into the interplay between symmetries and boundary conditions.
title Spin-$s$ $Q$-systems: Twist and Open Boundaries
topic High Energy Physics - Theory
Statistical Mechanics
Mathematical Physics
Exactly Solvable and Integrable Systems
url https://arxiv.org/abs/2502.15636