$q$-deformation of chromatic polynomials and graphical arrangements

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Main Authors: Nian, Tongyu, Tsujie, Shuhei, Uchiumi, Ryo, Yoshinaga, Masahiko
Format: Preprint
Published: 2024
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_version_ 1866916675771695104
author Nian, Tongyu
Tsujie, Shuhei
Uchiumi, Ryo
Yoshinaga, Masahiko
author_facet Nian, Tongyu
Tsujie, Shuhei
Uchiumi, Ryo
Yoshinaga, Masahiko
contents We first observe a mysterious similarity between the braid arrangement and the arrangement of all hyperplanes in a vector space over the finite field $\mathbb{F}_q$. These two arrangements are defined by the determinants of the Vandermonde and the Moore matrix, respectively. These two matrices are transformed to each other by replacing a natural number $n$ with $q^n$ ($q$-deformation). In this paper, we introduce the notion of ``$q$-deformation of graphical arrangements'' as certain subarrangements of the arrangement of all hyperplanes over $\mathbb{F}_q$. This new class of arrangements extends the relationship between the Vandermonde and Moore matrices to graphical arrangements. We show that many invariants of the ``$q$-deformation'' behave as ``$q$-deformation'' of invariants of the graphical arrangements. Such invariants include the characteristic (chromatic) polynomial, the Stirling number of the second kind, freeness, exponents, basis of logarithmic vector fields, etc.
format Preprint
id arxiv_https___arxiv_org_abs_2412_08290
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle $q$-deformation of chromatic polynomials and graphical arrangements
Nian, Tongyu
Tsujie, Shuhei
Uchiumi, Ryo
Yoshinaga, Masahiko
Combinatorics
Rings and Algebras
We first observe a mysterious similarity between the braid arrangement and the arrangement of all hyperplanes in a vector space over the finite field $\mathbb{F}_q$. These two arrangements are defined by the determinants of the Vandermonde and the Moore matrix, respectively. These two matrices are transformed to each other by replacing a natural number $n$ with $q^n$ ($q$-deformation). In this paper, we introduce the notion of ``$q$-deformation of graphical arrangements'' as certain subarrangements of the arrangement of all hyperplanes over $\mathbb{F}_q$. This new class of arrangements extends the relationship between the Vandermonde and Moore matrices to graphical arrangements. We show that many invariants of the ``$q$-deformation'' behave as ``$q$-deformation'' of invariants of the graphical arrangements. Such invariants include the characteristic (chromatic) polynomial, the Stirling number of the second kind, freeness, exponents, basis of logarithmic vector fields, etc.
title $q$-deformation of chromatic polynomials and graphical arrangements
topic Combinatorics
Rings and Algebras
url https://arxiv.org/abs/2412.08290