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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…

Combinatorics · Mathematics 2024-10-28 Gergely Bérczi , Jonas Klüver

Let $\mathcal{C} = \{c_1,c_2, c_3, \ldots,c_k\}$ be a certain type of proper $k$-colouring of a given graph $G$ and $\theta(c_i)$ denote the number of times a particular colour $c_i$ is assigned to the vertices of $G$. Then, the colouring…

General Mathematics · Mathematics 2016-06-02 N. K. Sudev , K. P. Chithra , Johan Kok

Shareshian-Wachs, Brosnan-Chow, and Guay-Pacquet [Adv. Math. ${\bf 295}$ (2016), ${\bf 329}$ (2018), arXiv:1601.05498] realized the chromatic (quasi-)symmetric function of a unit interval graph in terms of Hessenberg varieties. Here we…

Combinatorics · Mathematics 2024-10-18 Syu Kato

We define a number of related combinatorial objects, each of which possesses a surprising symmetry. We include several applications such as a combinatorial explanation for certain fixed points of the involution $\omega$ on the ring of…

Combinatorics · Mathematics 2018-09-13 Graham Hawkes

In this paper, we investigate the strength of chromatic symmetric homology as a graph invariant. Chromatic symmetric homology is a lift of the chromatic symmetric function for graphs to a homological setting, and its Frobenius…

Combinatorics · Mathematics 2019-12-02 Alex Chandler , Radmila Sazdanovic , Salvatore Stella , Martha Yip

We construct examples of nonnegative harmonic functions on certain graded graphs: the Young lattice and its generalizations. Such functions first emerged in harmonic analysis on the infinite symmetric group. Our method relies on…

Combinatorics · Mathematics 2016-09-07 Alexei Borodin , Grigori Olshanski

We present an algebraic characterization of perfect graphs, i.e., graphs for which the clique number and the chromatic number coincide for every induced subgraph. We show that a graph is perfect if and only if certain nonnegative…

Optimization and Control · Mathematics 2023-05-03 Amir Ali Ahmadi , Cemil Dibek

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…

Combinatorics · Mathematics 2020-02-06 Olivier Bernardi , Philippe Nadeau

We introduce a class of pairs of graphs consisting of two cliques joined by an arbitrary number of edges. The members of a pair have the property that the clique-bridging edge-set of one graph is the complement of that of the other. We…

Combinatorics · Mathematics 2011-06-08 Adam Bohn

The chromatic quasisymmetric function of a graph was introduced by Shareshian and Wachs as a refinement of Stanley's chromatic symmetric function. An explicit combinatorial formula, conjectured by Shareshian and Wachs, expressing the…

Combinatorics · Mathematics 2015-04-28 Christos A. Athanasiadis

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…

Combinatorics · Mathematics 2022-09-29 Logan Crew , Evan Haithcock , Josephine Reynes , Sophie Spirkl

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…

Combinatorics · Mathematics 2017-09-07 Brittney Ellzey

A well-known open problem in graph theory asks whether Stanley's chromatic symmetric function, a generalization of the chromatic polynomial of a graph, distinguishes between any two non-isomorphic trees. Previous work has proven the…

Combinatorics · Mathematics 2020-02-05 Jake Huryn

In the mid-1990s, Stanley and Stembridge conjectured that the chromatic symmetric functions of claw-free co-comparability (also called incomparability) graphs were e-positive. The quest for the proof of this conjecture has led to an…

Combinatorics · Mathematics 2018-08-13 Angèle M. Foley , Chính T. Hoàng , Owen D. Merkel

In this paper, we consider the generating functions of the complete and elementary symmetric functions and provide a new generalization of these classical symmetric functions. Some classical relationships involving the complete and…

Combinatorics · Mathematics 2020-05-05 Moussa Ahmia , Mircea Merca

Two celebrated conjectures in chromatic symmetric function theory concern the positivity chromatics symmetric functions of claw-free graphs. Here we extend the claw-free idea to general graphs and consider the e-positivity question for…

Combinatorics · Mathematics 2017-09-12 Angèle M. Hamel , Chính T. Hoàng , Jake E. Tuero

Motivated by the study of Macdonald polynomials, J. Haglund and A. Wilson introduced a nonsymmetric polynomial analogue of the chromatic quasisymmetric function called the \emph{chromatic nonsymmetric polynomial} of a Dyck graph. We give a…

Combinatorics · Mathematics 2019-08-20 Vasu Tewari , Andrew Timothy Wilson , Philip B. Zhang

Finite graphs that have a common chromatic polynomial have the same number of regular $n$-colorings. A natural question is whether there exists a natural bijection between regular $n$-colorings. We address this question using a functorial…

Combinatorics · Mathematics 2015-08-12 Masahiko Yoshinaga

The goal of the paper is to apply the general operator theoretic construction known as the Schur complement for computation of the spectrum of certain infinite graphs which can be viewed as finite graphs with the ray attached to them. The…

Combinatorics · Mathematics 2015-04-20 L. Golinskii

Mason and Remmel introduced a basis for quasisymmetric functions known as the row-strict quasisymmetric Schur functions. This basis is generated combinatorially by fillings of composition diagrams that are analogous to the row-strict…

Combinatorics · Mathematics 2021-05-31 Sarah K. Mason , Elizabeth Niese