Combinatorial invariance for the coefficient of $q$ in Kazhdan-Lusztig polynomials

Fuente: arXiv
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Main Authors: Barkley, Grant T., Gaetz, Christian, Lam, Thomas
Format: Preprint
Published: 2026
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author Barkley, Grant T.
Gaetz, Christian
Lam, Thomas
author_facet Barkley, Grant T.
Gaetz, Christian
Lam, Thomas
contents We prove the combinatorial invariance of the coefficient of $q$ in Kazhdan--Lusztig polynomials for arbitrary Coxeter groups. As a result, we obtain the Combinatorial Invariance Conjecture, of Lusztig and of Dyer, also for Bruhat intervals of length at most $6$. We also prove the Gabber--Joseph conjecture for the second-highest $Ext$ group of a pair of Verma modules, as well as the combinatorial invariance of the dimension of this group, and of the numbers of frozen and of mutable variables in the cluster structure on Richardson varieties.
format Preprint
id arxiv_https___arxiv_org_abs_2601_07793
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Combinatorial invariance for the coefficient of $q$ in Kazhdan-Lusztig polynomials
Barkley, Grant T.
Gaetz, Christian
Lam, Thomas
Combinatorics
Representation Theory
20F55 (Primary) 14M15, 17B10 (Secondary)
We prove the combinatorial invariance of the coefficient of $q$ in Kazhdan--Lusztig polynomials for arbitrary Coxeter groups. As a result, we obtain the Combinatorial Invariance Conjecture, of Lusztig and of Dyer, also for Bruhat intervals of length at most $6$. We also prove the Gabber--Joseph conjecture for the second-highest $Ext$ group of a pair of Verma modules, as well as the combinatorial invariance of the dimension of this group, and of the numbers of frozen and of mutable variables in the cluster structure on Richardson varieties.
title Combinatorial invariance for the coefficient of $q$ in Kazhdan-Lusztig polynomials
topic Combinatorics
Representation Theory
20F55 (Primary) 14M15, 17B10 (Secondary)
url https://arxiv.org/abs/2601.07793