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arXiv · 2510.15241

Orbits and self-twuality in set systems and delta-matroids

Zhuo Li·Xian'an Jin·Qi Yan
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Abstract

We introduce a new group action on set systems, constructed as a semidirect product of a permutation group and a group generated by twist and loop complementation operations on a single element. This action extends the ribbon group framework of Abrams and Ellis-Monaghan from ribbon graphs to set systems, facilitating a systematic investigation of self-twuality. We prove that different forms of self-twuality propagate through orbits under the group action and establish a characterization of the orbit of a vf-safe delta-matroid via multimatroids. As an application, we analyze orbits of ribbon-graphic delta-matroids. Our work answers a question posed by Abrams and Ellis-Monaghan and provides a unified algebraic framework for studying self-twuality in combinatorial structures.

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Zhuo Li, Xian'an Jin, Qi Yan. 2025-10-17. Orbits and self-twuality in set systems and delta-matroids. https://arxiv.org/abs/2510.15241

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