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In this note we classify when a skew Schur function is a positive linear combination of power sum symmetric functions. We then use this to determine precisely when any scalar multiple of a skew Schur function is the chromatic symmetric…

组合数学 · 数学 2018-09-03 Soojin Cho , Stephanie van Willigenburg

We introduce path-conjoined graphs defined for two rooted graphs by joining their roots with a path, and investigate the chromatic symmetric functions of its two generalizations: spider-conjoined graphs and chain-conjoined graphs. By using…

组合数学 · 数学 2026-02-04 E. Y. J. Qi , D. Q. B. Tang , D. G. L. Wang

A graph is Schur-positive if its chromatic symmetric function expands nonnegatively in the Schur basis. All claw-free graphs are conjectured to be Schur-positive. We introduce a combinatorial object corresponding to a graph G, called a…

组合数学 · 数学 2024-12-24 Ethan Shelburne , Stephanie van Willigenburg

Crew and Spirklt generalize Stanley's chromatic symmetric function to vertex-weighted graphs. One of the primary motivations for extending the chromatic symmetric function to vertex-weighted graphs is the existence of a deletion-contraction…

组合数学 · 数学 2023-08-08 Azzurra Ciliberti

Schur functions are a basis of the symmetric function ring that represent Schubert cohomology classes for Grassmannians. Replacing the cohomology ring with $K$-theory yields a rich combinatorial theory of inhomogeneous deformations, where…

组合数学 · 数学 2023-05-19 Logan Crew , Oliver Pechenik , Sophie Spirkl

We prove some Schur positivity results for the chromatic symmetric function $X_G$ of a (hyper)graph $G$, using connections to the group algebra of the symmetric group. The first such connection works for (hyper)forests $F$: we describe the…

组合数学 · 数学 2024-10-29 Brendan Pawlowski

We investigate chromatic symmetric functions in the relation to the algebra $\Gamma$ of symmetric functions generated by Schur $Q$-functions. We construct natural bases of $\Gamma$ in terms of chromatic symmetric functions. We also consider…

组合数学 · 数学 2019-07-24 Soojin Cho , JiSun Huh , Sun-Young Nam

In this note we obtain numerous new bases for the algebra of symmetric functions whose generators are chromatic symmetric functions. More precisely, if $\{ G_ k \}_{k\geq 1}$ is a set of connected graphs such that $G_k$ has $k$ vertices for…

组合数学 · 数学 2016-08-31 Soojin Cho , Stephanie van Willigenburg

We focus on two specific generalizations of the chromatic symmetric function: one involving universal graphs and the other concerning vertex-weighted graphs. In this paper, we introduce a unified generalization that incorporates both…

组合数学 · 数学 2025-04-01 Yosuke Sato

We extend the definition of the chromatic symmetric function $X_G$ to include graphs $G$ with a vertex-weight function $w : V(G) \rightarrow \mathbb{N}$. We show how this provides the chromatic symmetric function with a natural…

组合数学 · 数学 2020-01-16 Logan Crew , Sophie Spirkl

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

We make a systematic study of a new combinatorial construction called a dual equivalence graph. We axiomatize these graphs and prove that their generating functions are symmetric and Schur positive. This provides a universal method for…

组合数学 · 数学 2020-03-05 Sami H. Assaf

Stanley introduced the chromatic symmetric function of a simple graph, which is a generalization of a chromatic polynomial. This is expressed in terms of the integer points of the complements of the corresponding graphic arrangement.…

组合数学 · 数学 2021-03-05 Masamichi Kuroda , Shuhei Tsujie

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

We define an equivalence relation on integer compositions and show that two ribbon Schur functions are identical if and only if their defining compositions are equivalent in this sense. This equivalence is completely determined by means of…

组合数学 · 数学 2007-06-20 Louis J. Billera , Hugh Thomas , Stephanie van Willigenburg

A graph is Schur-positive if its chromatic symmetric function expands non-negatively in the Schur basis. We determine a full Schur-positivity classification for complete multipartite graphs by showing that a complete multipartite graph…

组合数学 · 数学 2026-04-30 Ethan Shelburne , Stephanie van Willigenburg

We express the integral form Macdonald polynomials as a weighted sum of Shareshian and Wachs' chromatic quasisymmetric functions of certain graphs. Then we use known expansions of these chromatic quasisymmetric functions into Schur and…

组合数学 · 数学 2018-03-26 James Haglund , Andrew Timothy Wilson

This paper has two main parts. First, we consider the Tutte symmetric function $XB$, a generalization of the chromatic symmetric function. We introduce a vertex-weighted version of $XB$ and show that this function admits a…

组合数学 · 数学 2021-10-04 José Aliste-Prieto , Logan Crew , Sophie Spirkl , José Zamora

We introduce a quasisymmetric refinement of Stanley's chromatic symmetric function. We derive refinements of both Gasharov's Schur-basis expansion of the chromatic symmetric function and Chow's expansion in Gessel's basis of fundamental…

组合数学 · 数学 2016-03-30 John Shareshian , Michelle L. Wachs

We prove necessary conditions for certain elementary symmetric functions, $e_\lambda$, to appear with nonzero coefficient in Stanley's chromatic symmetric function as well as in the generalization considered by Shareshian and Wachs. We do…

组合数学 · 数学 2024-07-09 Bruce E. Sagan , Foster Tom
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