Extended Weak Order for the Rank 3 Universal Coxeter Group

Fuente: arXiv
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Autori principali: Barkley, Grant, Defant, Colin, Hersh, Patricia, McCammond, Jon, McConville, Thomas, Speyer, David E
Natura: Preprint
Pubblicazione: 2025
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_version_ 1866912562925273088
author Barkley, Grant
Defant, Colin
Hersh, Patricia
McCammond, Jon
McConville, Thomas
Speyer, David E
author_facet Barkley, Grant
Defant, Colin
Hersh, Patricia
McCammond, Jon
McConville, Thomas
Speyer, David E
contents The weak order is a classical poset structure on a Coxeter group; it is a lattice when the group is finite but merely a meet-semilattice when the group is infinite. Motivated by problems in Kazhdan--Lusztig theory, Matthew Dyer introduced the extended weak order, a poset that contains a copy of the weak order as an order ideal, and he conjectured that the extended weak order for any Coxeter group is a lattice. We prove Dyer's conjecture for the rank 3 universal Coxeter group. This is the first non-spherical, non-affine Coxeter group for which Dyer's conjecture has been proven.
format Preprint
id arxiv_https___arxiv_org_abs_2509_00871
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Extended Weak Order for the Rank 3 Universal Coxeter Group
Barkley, Grant
Defant, Colin
Hersh, Patricia
McCammond, Jon
McConville, Thomas
Speyer, David E
Combinatorics
Group Theory
20F55, 17B22, 06B23
The weak order is a classical poset structure on a Coxeter group; it is a lattice when the group is finite but merely a meet-semilattice when the group is infinite. Motivated by problems in Kazhdan--Lusztig theory, Matthew Dyer introduced the extended weak order, a poset that contains a copy of the weak order as an order ideal, and he conjectured that the extended weak order for any Coxeter group is a lattice. We prove Dyer's conjecture for the rank 3 universal Coxeter group. This is the first non-spherical, non-affine Coxeter group for which Dyer's conjecture has been proven.
title Extended Weak Order for the Rank 3 Universal Coxeter Group
topic Combinatorics
Group Theory
20F55, 17B22, 06B23
url https://arxiv.org/abs/2509.00871