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The chromatic polynomial and its generalization, the chromatic symmetric function, are two important graph invariants. Celebrated theorems of Birkhoff, Whitney, and Stanley show how both objects can be expressed in three different ways: as…

Combinatorics · Mathematics 2020-07-28 Bruce E. Sagan , Vincent Vatter

Chromatic symmetric functions are well-studied symmetric functions in algebraic combinatorics that generalize the chromatic polynomial and are related to Hessenberg varieties and diagonal harmonics. Motivated by the Stanley--Stembridge…

Combinatorics · Mathematics 2025-02-11 Jacob P. Matherne , Alejandro H. Morales , Jesse Selover

In this article we are introducing combinatorial spectra of graphs, this is a generalization of $H$-Hamiltonian spectra. The main motivation was to made from $H$-Hamiltonian spectra an operation and develop some algebra in this field. An…

Combinatorics · Mathematics 2023-11-21 Martin Dzúrik

In 1995 Stanley introduced the chromatic symmetric function $X_G$ of a graph $G$, whose $e$-positivity and Schur-positivity has been of large interest. In this paper we study the relative $e$-positivity and Schur-positivity between…

Combinatorics · Mathematics 2020-03-16 Samantha Dahlberg , Adrian She , Stephanie van Willigenburg

Khovanov introduced a bigraded cohomology theory of links whose graded Euler characteristic is the Jones polynomial. The theory was subsequently applied to the chromatic polynomial of graph, resulting in a categorification known as the…

Geometric Topology · Mathematics 2023-08-01 So Yamagata

We prove that a graph with a cut vertex whose deletion produces at least five connected components must be missing a connected partition of some type. We prove that this also holds if there are four connected components that each have at…

Combinatorics · Mathematics 2026-01-16 Foster Tom

Recall that the minimum number of colors that allow a proper coloring of graph $G$ is called the chromatic number of $G$ and denoted by $\chi(G).$ In this paper the concepts of $\chi$'-chromatic sum and $\chi^+$-chromatic sum are…

General Mathematics · Mathematics 2016-02-12 Johan Kok , Saptarshi Bej

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…

Combinatorics · Mathematics 2023-05-19 Logan Crew , Oliver Pechenik , Sophie Spirkl

Chromatic polynomials and related graph invariants are central objects in both graph theory and statistical physics. Computational difficulties, however, have so far restricted studies of such polynomials to graphs that were either very…

Statistical Mechanics · Physics 2017-09-20 Frank Van Bussel , Christoph Ehrlich , Denny Fliegner , Sebastian Stolzenberg , Marc Timme

As introduced by Gutman and Harary, the independence polynomial of a graph serves as the generating polynomial of its independent sets. In 1987, Alavi, Malde, Schwenk and Erd\H{o}s conjectured that the independence polynomials of all trees…

Combinatorics · Mathematics 2025-01-09 Ethan Y. H. Li , Grace M. X. Li , Arthur L. B. Yang , Zhong-Xue Zhang

Motivated by a connection between the topology of (generalized) configuration spaces and chromatic polynomials, we show that generating functions of Hodge-Deligne polynomials of quasiprojective varieties and colorings of acyclic directed…

Combinatorics · Mathematics 2022-03-23 Soohyun Park

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

The chromatic symmetric function $X_G$ is a sum of monomials corresponding to proper vertex colorings of a graph $G$. Crew, Pechenik, and Spirkl (2023) recently introduced a $K$-theoretic analogue $\overline{X}_G$ called the Kromatic…

Combinatorics · Mathematics 2025-02-21 Laura Pierson

We study the symmetric function and polynomial combinatorial invariants of Hopf algebras of permutations, posets and graphs. We investigate their properties and the relations among them. In particular, we show that the chromatic symmetric…

Combinatorics · Mathematics 2020-10-01 Jean-christophe Aval , Nantel Bergeron , John Machacek

We define the chromatic measure of a finite simple graph as the uniform distribution on its chromatic roots. We show that for a Benjamini-Schramm convergent sequence of finite graphs, the chromatic measures converge in holomorphic moments.…

Combinatorics · Mathematics 2013-05-20 Miklós Abért , Tamás Hubai

The chromatic polynomial is characterized as the unique polynomial invariant of graphs, compatible with two interacting bialgebras structures: the first coproduct is given by partitions of vertices into two parts, the second one by a…

Rings and Algebras · Mathematics 2021-05-05 Loïc Foissy

Various results ensure the existence of large complete bipartite graphs in properly colored graphs when some condition related to a topological lower bound on the chromatic number is satisfied. We generalize three theorems of this kind,…

Combinatorics · Mathematics 2017-04-04 Meysam Alishahi , Hossein Hajiabolhassan , Frédéric Meunier

We establish a set of recursion relations for the coefficients in the chromatic polynomial of a graph or a hypergraph. As an application we provide a generalization of Whitney's broken cycle theorem for hypergraphs, as well as deriving an…

Combinatorics · Mathematics 2022-01-04 Bergfinnur Durhuus , Angelo Lucia

We study the chromatic quasisymmetric class function of a linearized combinatorial Hopf monoid. Given a linearized combinatorial Hopf monoid $H$, and an $H$-structure $h$ on a set $N$, there are proper colorings of $h$, generalizing graph…

Combinatorics · Mathematics 2022-10-11 Jacob A. White

In this article we show how to compute the chromatic quasisymmetric function of indifference graphs from the modular law introduced by Guay-Paquet. We provide an algorithm which works for any function that satisfies this law, such as…

Combinatorics · Mathematics 2020-06-23 Alex Abreu , Antonio Nigro
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