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Related papers: Kazhdan-Lusztig polynomials of thagomizer matroids

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We report on various results, conjectures, and open problems related to Kazhdan-Lusztig polynomials of matroids. We focus on conjectures about the roots of these polynomials, all of which appear here for the first time.

Combinatorics · Mathematics 2017-03-16 Katie Gedeon , Nicholas Proudfoot , Benjamin Young

We define the equivariant Kazhdan-Lusztig polynomial of a matroid equipped with a group of symmetries, generalizing the nonequivariant case. We compute this invariant for arbitrary uniform matroids and for braid matroids of small rank.

Combinatorics · Mathematics 2016-11-23 Katie Gedeon , Nicholas Proudfoot , Ben Young

In this paper, we focus on the equivariant inverse Kazhdan--Lusztig polynomials of thagomizer matroids, a natural family of graphic matroids associated with the complete tripartite graphs $K_{1,1,n}$. These polynomials were introduced by…

Combinatorics · Mathematics 2025-10-14 Alice L. L. Gao , Yun Li , Matthew H. Y. Xie

The equivariant Kazhdan-Lusztig polynomial of a matroid was introduced by Gedeon, Proudfoot, and Young. Gedeon conjectured an explicit formula for the equivariant Kazhdan-Lusztig polynomials of thagomizer matroids with an action of…

Combinatorics · Mathematics 2019-02-05 Matthew H. Y. Xie , Philip B. Zhang

We introduce the Z-polynomial of a matroid, which we define in terms of the Kazhdan-Lusztig polynomial. We then exploit a symmetry of the Z-polynomial to derive a new recursion for Kazhdan-Lusztig coefficients. We solve this recursion,…

Combinatorics · Mathematics 2017-06-20 Nicholas Proudfoot , Ben Young , Yuan Xu

We associate to every matroid M a polynomial with integer coefficients, which we call the Kazhdan-Lusztig polynomial of M, in analogy with Kazhdan-Lusztig polynomials in representation theory. We conjecture that the coefficients are always…

Combinatorics · Mathematics 2016-07-04 Ben Elias , Nicholas Proudfoot , Max Wakefield

The thagomizer matroid, realized as the graphic matroid of the complete tripartite graph $K_{1,1,n}$, has full automorphism group isomorphic to the hyperoctahedral group whenever $n \ge 2$. In the equivariant setting for this action, we…

Combinatorics · Mathematics 2026-02-12 Matthew H. Y. Xie , Philip B. Zhang , Michael X. X. Zhong

We study the way in which equivariant Kazhdan-Lusztig polynomials, equivariant inverse Kazhdan-Lusztig polynomials, and equivariant Z-polynomials of matroids change under the operation of relaxation of a collection of stressed hyperplanes.…

Combinatorics · Mathematics 2022-02-15 Trevor Karn , George Nasr , Nicholas Proudfoot , Lorenzo Vecchi

We give a concrete combinatorial interpretation of the coefficients of the Kazhdan-Lusztig polynomials of Dowling geometries, a family of matroids which generalizes braid matroids of types A and B. Furthermore, we interpret the coefficients…

Combinatorics · Mathematics 2026-05-06 Luis Ferroni , Matt Larson

The Kazhdan-Lusztig polynomial of a matroid was introduced by Elias, Proudfoot and Wakefield, whose properties need to be further explored. In this paper we prove that the Kazhdan-Lusztig polynomials of fan matroids coincide with Motzkin…

Combinatorics · Mathematics 2018-02-13 Linyuan Lu , Matthew H. Y. Xie , Arthur L. B. Yang

Motivated by the concepts of the inverse Kazhdan-Lusztig polynomial and the equivariant Kazhdan-Lusztig polynomial, Proudfoot defined the equivariant inverse Kazhdan-Lusztig polynomial for a matroid. In this paper, we show that the…

Combinatorics · Mathematics 2021-05-19 Alice L. L. Gao , Matthew H. Y. Xie , Arthur L. B. Yang

We present a formula which relates the Kazhdan-Lusztig polynomial of a matroid $M$, as defined by Elias, Proudfoot and Wakefield, to the Kazhdan--Lusztig polynomials of the matroid obtained by deleting an element, and various contractions…

Combinatorics · Mathematics 2023-06-13 Tom Braden , Artem Vysogorets

We compute the Kazhdan-Lusztig polynomial of the uniform matroid of rank n-1 on n elements by proving that the i-th coefficient of is equal to the number of ways to choose i non-intersecting chords in an (n-i+1)-gon. We also show that the…

Combinatorics · Mathematics 2015-12-22 Nicholas Proudfoot , Max Wakefield , Benjamin Young

Gao and Xie (2021) conjectured that the inverse Kazhdan-Lusztig polynomial of any matroid is log-concave. Although the inverse Kazhdan-Lusztig polynomial may not always have only real roots, we conjecture that the Hadamard product of an…

Combinatorics · Mathematics 2025-04-25 Matthew H. Y. Xie , Philip B. Zhang

We prove the positivity of Kazhdan-Lusztig polynomials for sparse paving matroids, which are known to be logarithmically almost all matroids, but are conjectured to be almost all matroids. The positivity follows from a remarkably simple…

Combinatorics · Mathematics 2020-06-19 Kyungyong Lee , George D. Nasr , Jamie Radcliffe

The Kazhdan-Lusztig polynomial of a matroid was introduced by Elias, Proudfoot, and Wakefield [{\it Adv. Math. 2016}]. Let $U_{m,d}$ denote the uniform matroid of rank $d$ on a set of $m+d$ elements. Gedeon, Proudfoot, and Young [{\it J.…

Combinatorics · Mathematics 2018-06-29 Alice L. L. Gao , Linyuan Lu , Matthew H. Y. Xie , Arthur L. B. Yang , Philip B. Zhang

We provide a combinatorial interpretation of the Kazhdan--Lusztig polynomial of the matroid arising from the braid arrangement of type $\mathrm{A}_{n-1}$, which gives an interpretation of the intersection cohomology Betti numbers of the…

Combinatorics · Mathematics 2024-01-31 Luis Ferroni , Matt Larson

We introduce $q$-analogues of uniform matroids, which we call $q$-niform matroids. While uniform matroids admit actions of symmetric groups, $q$-niform matroids admit actions of finite general linear groups. We show that the equivariant…

Combinatorics · Mathematics 2018-09-05 Nicholas Proudfoot

Kazhdan-Lusztig-Stanley polynomials are a combinatorial generalization of Kazhdan-Lusztig polynomials of for Coxeter groups that include g-polynomials of polytopes and Kazhdan-Lusztig polynomials of matroids. In the cases of Weyl groups,…

Algebraic Geometry · Mathematics 2018-06-15 Nicholas Proudfoot

In analogy with the classical Kazhdan-Lusztig polynomials for Coxeter groups, Elias, Proudfoot and Wakefield introduced the concept of Kazhdan-Lusztig polynomials for matroids. It is known that both the classical Kazhdan-Lusztig polynomials…

Combinatorics · Mathematics 2021-08-16 Alice L. L. Gao , Matthew H. Y. Xie
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