English

Combinatorics of cone types in Coxeter groups

Group Theory 2026-05-06 v6 Combinatorics

Abstract

In this article, we establish some new combinatorial properties of cone types in Coxeter groups. Firstly, we show that for any element xx in a Coxeter group WW and root β\beta in its inversion set Φ(x)\Phi(x), the set of elements yWy \in W satisfying Φ(x)Φ(y)={β}\Phi(x) \cap \Phi(y) = \{ \beta \} is convex in the weak order and admits a unique minimal representative. This is strongly connected to determining the cone type of elements of WW and leads to efficient computational methods to determine whether arbitrary elements of WW have the same cone type.

Keywords

Cite

@article{arxiv.2410.22599,
  title  = {Combinatorics of cone types in Coxeter groups},
  author = {Yeeka Yau},
  journal= {arXiv preprint arXiv:2410.22599},
  year   = {2026}
}

Comments

We were made aware that Theorem 1 in the previous version is Theorem 8.1 in Reading and Speyer, "Sortable elements in infinite Coxeter groups, Transactions of the American Mathematical Society (2011), so the paper has been reorganised and exposition has been updated. Our alternative proof of Theorem 8.1 of Reading and Speyer has been repositioned to the last complimentary section

R2 v1 2026-06-28T19:40:30.108Z