Non-commutative frieze patterns over quaternion algebras and other normed division rings
Abstract
Non-commutative friezes have been introduced by Berenstein and Retakh and studied further by the authors. In this paper we consider non-commutative friezes over normed division rings, like for instance Hamilton's quaternions or more general quaternion algebras. We address the fundamental question in the theory of friezes of whether over a certain subset there are finitely or infinitely many non-commutative friezes (with 1's on the boundary) for any height. As an application of a theorem bounding the norm of quiddity entries we deduce that for every norm-finite subset of a normed division ring there are only finitely many such non-commutative friezes for every height. In particular this result applies to the Lipschitz quaternions and the Hurwitz quaternions of Hamilton's quaternions. We then study more generally non-commutative friezes over Lipschitz subrings of non-split quaternion algebras (a,b)ℚ. We determine the frieze subrings for all a,b<0, and as a consequence we see that all such non-commutative friezes are known if a≤ −4 and b≤ −4.
Related
BibTeX
@misc{cuntz2026noncommutative,
title = {{Non-commutative frieze patterns over quaternion algebras and other normed division rings}},
author = {Michael Cuntz and Thorsten Holm and Peter Jorgensen},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.32257},
eprint = {2609.32257},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.32257},
}
RIS
TY - UNPB
TI - Non-commutative frieze patterns over quaternion algebras and other normed division rings
AU - Michael Cuntz
AU - Thorsten Holm
AU - Peter Jorgensen
PY - 2026
DA - 2026/09/26
PB - arXiv
DO - 10.48550/arxiv.2609.32257
UR - https://arxiv.org/abs/2609.32257
AB - Non-commutative friezes have been introduced by Berenstein and Retakh and studied further by the authors. In this paper we consider non-commutative friezes over normed division rings, like for instance Hamilton's quaternions or more general quaternion algebras. We address the fundamental question in the theory of friezes of whether over a certain subset there are finitely or infinitely many non-commutative friezes (with 1's on the boundary) for any height. As an application of a theorem bounding the norm of quiddity entries we deduce that for every norm-finite subset of a normed division ring there are only finitely many such non-commutative friezes for every height. In particular this result applies to the Lipschitz quaternions and the Hurwitz quaternions of Hamilton's quaternions. We then study more generally non-commutative friezes over Lipschitz subrings of non-split quaternion algebras (a,b)_ℚ. We determine the frieze subrings for all a,b<0, and as a consequence we see that all such non-commutative friezes are known if a≤ −4 and b≤ −4.
ER -