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We describe how the chromatic symmetric function of two graphs glued at a single vertex can be expressed as a matrix multiplication using certain information of the two individual graphs. We then prove new $e$-positivity results by using a…

组合数学 · 数学 2025-03-26 Foster Tom , Aarush Vailaya

In 1993, Stanley and Stembridge conjectured that a chromatic symmetric function of any $(3+1)$-free poset is $e$-positive. Guay-Paquet reduced the conjecture to $(3+1)$- and $(2+2)$-free posets which are also called natural unit interval…

组合数学 · 数学 2022-02-15 Seung Jin Lee , Sue Kyong Y. Soh

Richard P. Stanley defined the chromatic symmetric function of a simple graph and has conjectured that every tree is determined by its chromatic symmetric function. Recently, Takahiro Hasebe and the author proved that the order…

组合数学 · 数学 2018-07-23 Shuhei Tsujie

We propose a conjectural counting formula for the coefficients of the chromatic symmetric function of unit interval graphs using reinforcement learning. The formula counts specific disjoint cycle-tuples in the graphs, referred to as…

组合数学 · 数学 2024-10-28 Gergely Bérczi , Jonas Klüver

In this paper, we extend the chromatic symmetric function $X$ to a chromatic $k$-multisymmetric function $X_k$, defined for graphs equipped with a partition of their vertex set into $k$ parts. We demonstrate that this new function retains…

组合数学 · 数学 2022-09-29 Logan Crew , Evan Haithcock , Josephine Reynes , Sophie Spirkl

The chromatic symmetric function of a graph is a generalization of the chromatic polynomial. The key motivation for studying the structure of a chromatic symmetric function is to answer positivity conjectures by Stanley in 1995 and Gasharov…

组合数学 · 数学 2014-11-10 Ryan Kaliszewski

Let G be a graph, and let $\chi$G be its chromatic polynomial. For any non-negative integers i, j, we give an interpretation for the evaluation $\chi$ (i) G (--j) in terms of acyclic orientations. This recovers the classical interpretations…

组合数学 · 数学 2020-02-06 Olivier Bernardi , Philippe Nadeau

We prove a new signed elementary symmetric function expansion of the chromatic quasisymmetric function of any natural unit interval graph. We then use a sign-reversing involution to prove a new combinatorial formula for K-chains, which are…

组合数学 · 数学 2024-05-09 Foster Tom

For a natural unit interval order $P$, we describe proper colorings of the incomparability graph of $P$ in the language of heaps. We also introduce a combinatorial operation, called a \emph{local flip}, on the heaps. This operation defines…

组合数学 · 数学 2024-04-22 Byung-Hak Hwang

In the vector space of symmetric functions, the elements of the basis of elementary symmetric functions are (up to a factor) the chromatic symmetric functions of disjoint unions of cliques. We consider their graph complements, the functions…

组合数学 · 数学 2021-11-16 Logan Crew , Sophie Spirkl

We introduce $H$-chromatic symmetric functions, $X_{G}^{H}$, which use the $H$-coloring of a graph $G$ to define a generalization of Stanley's chromatic symmetric functions. We say two graphs $G_1$ and $G_2$ are $H$-chromatically equivalent…

组合数学 · 数学 2022-05-23 Nancy Mae Eagles , Angèle M. Foley , Alice Huang , Elene Karangozishvili , Annan Yu

Stanley defined the chromatic symmetric function of a graph, and Shareshian and Wachs introduced a refinement, namely the chromatic quasisymmetric function of a labeled graph. In this paper, we define the chromatic quasisymmetric function…

组合数学 · 数学 2017-09-07 Brittney Ellzey

Combinatorics, in particular graph theory, has a rich history of being a domain of successful applications of tools from other areas of mathematics, including topological methods. Here, we survey the study of the Hom-complexes, and the ways…

代数拓扑 · 数学 2007-05-23 Dmitry N. Kozlov

We establish Guay-Paquet's unpublished linear relation between certain chromatic symmetric functions by relating his algebra on paths to the $q$-Klyachko algebra. The coefficients in this relations are $q$-hit polynomials, and they come up…

组合数学 · 数学 2022-08-09 Philippe Nadeau , Vasu Tewari

Chromatic quasisymmetric functions of labeled graphs were defined by Shareshian and Wachs as a refinement of Stanley's chromatic symmetric functions. In this extended abstract, we consider an extension of their definition from labeled…

组合数学 · 数学 2017-04-17 Brittney Ellzey

In Stanley's seminal 1995 paper on the chromatic symmetric function, he stated that there was no known graph that was not contractible to the claw and whose chromatic symmetric function was not $e$-positive, namely, not a positive linear…

组合数学 · 数学 2020-05-21 Samantha Dahlberg , Angele Foley , Stephanie van Willigenburg

For a $(3+1)$-free poset $P$, we define a hybrid of $P$-tableaux and cylindric tableaux called cylindric $P$-tableaux. We introduce $P$-analogs of cylindric Schur functions, defined by a determinantal formula, and prove that they are the…

组合数学 · 数学 2022-11-10 Isaiah Siegl

Let $\mathfrak g$ be a Borcherds algebra with the associated graph $G$. We prove that the chromatic symmetric function of $G$ can be recovered from the Weyl denominator identity of $\mathfrak g$ and this gives a Lie theoretic proof of…

组合数学 · 数学 2021-05-21 G. Arunkumar

The machinery of noncommutative Schur functions is a general approach to Schur positivity of symmetric functions initiated by Fomin-Greene. Hwang recently adapted this theory to posets to give a new approach to the Stanley-Stembridge…

组合数学 · 数学 2022-11-10 Jonah Blasiak , Holden Eriksson , Pavlo Pylyavskyy , Isaiah Siegl

The chromatic quasisymmetric functions (csf) of Shareshian and Wachs associated to unit interval orders have attracted a lot of interest since their introduction in 2016, both in combinatorics and geometry, because of their relation to the…

组合数学 · 数学 2023-11-17 Michele D'Adderio , Roberto Riccardi , Viola Siconolfi