Annexes in affine Coxeter complexes

Fuente: arXiv
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Main Author: Masters, Megan
Format: Preprint
Published: 2026
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author Masters, Megan
author_facet Masters, Megan
contents We introduce the annex of an element $x$ in a Coxeter group as the set of elements $y$ such that $x \nleq y$ with respect to Bruhat order. This notion provides a complementary perspective to the study of Bruhat intervals and their interpretation via folded galleries. We establish general properties of annexes and show that in affine Coxeter groups the annex of any fixed element is finite. In rank-two affine Coxeter complexes, we further describe the geometric structure of annex boundaries using descent sets and configurations of parallel reflections. These results offer a new geometric viewpoint on the structure of the Bruhat order.
format Preprint
id arxiv_https___arxiv_org_abs_2603_15529
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Annexes in affine Coxeter complexes
Masters, Megan
Group Theory
Combinatorics
20F65, 20F55, 51F15, 20E42, 51E24, 05E45
We introduce the annex of an element $x$ in a Coxeter group as the set of elements $y$ such that $x \nleq y$ with respect to Bruhat order. This notion provides a complementary perspective to the study of Bruhat intervals and their interpretation via folded galleries. We establish general properties of annexes and show that in affine Coxeter groups the annex of any fixed element is finite. In rank-two affine Coxeter complexes, we further describe the geometric structure of annex boundaries using descent sets and configurations of parallel reflections. These results offer a new geometric viewpoint on the structure of the Bruhat order.
title Annexes in affine Coxeter complexes
topic Group Theory
Combinatorics
20F65, 20F55, 51F15, 20E42, 51E24, 05E45
url https://arxiv.org/abs/2603.15529