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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

We study the $H$-chromatic symmetric functions $X_G^H$ (introduced in (arXiv:2011.06063) as a generalization of the chromatic symmetric function (CSF) $X_G$), which track homomorphisms from the graph $G$ to the graph $H$. We focus first on…

Combinatorics · Mathematics 2025-11-13 Shao Yuan Lin , Laura Pierson

If we consider previously introduced extensions of Stanley's chromatic symmetric function $X_{G}(x_1, x_2, \ldots)$ for a graph $G$ to elements in the algebra $\textsf{QSym}$ of quasisymmetric functions and in the algebra $\textsf{NCSym}$…

Combinatorics · Mathematics 2024-10-08 John M. Campbell

In this text we introduce and analyze families of symmetric functions arising as partition functions for colored fermionic vertex models associated with the quantized affine Lie superalgebra $U_q \big( \widehat{\mathfrak{sl}} (1 | n)…

Combinatorics · Mathematics 2021-05-11 Amol Aggarwal , Alexei Borodin , Michael Wheeler

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

In this paper, we study positivity phenomena for the $e$-coefficients of Stanley's chromatic function of a graph. We introduce a new combinatorial object: the {\em correct} sequences of unit interval orders, and using these, in certain…

Combinatorics · Mathematics 2017-03-20 Alexander Paunov , András Szenes

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

This paper presents the basic properties of chromatic derivatives and chromatic expansions and provides an appropriate motivation for introducing these notions. Chromatic derivatives are special, numerically robust linear differential…

Classical Analysis and ODEs · Mathematics 2009-07-14 Aleksandar Ignjatovic

The orbital bivariate chromatic polynomial, introduced in this article, counts the number of ways to color the vertices of a graph with $\lambda$ colors such that adjacent vertices either receive distinct colors from a set of $\lambda$…

Combinatorics · Mathematics 2025-11-05 Klaus Dohmen , Mandy Lange-Geisler

We discover new linear relations between the chromatic symmetric functions of certain sequences of graphs and apply these relations to find new families of e-positive unit interval graphs. Motivated by the results of Gebhard and Sagan, we…

Combinatorics · Mathematics 2024-12-24 Farid Aliniaeifard , Victor Wang , Stephanie van Willigenburg

Motivated by Stanley's conjecture on the multiplication of Jack symmetric functions, we prove a couple of identities showing that skew Jack symmetric functions are semi-invariant up to translation and rotation of a $\pi$ angle of the skew…

Combinatorics · Mathematics 2021-07-02 Paolo Bravi , Jacopo Gandini

A \emph{chromatic root} is a root of the chromatic polynomial of a graph. Any chromatic root is an algebraic integer. Much is known about the location of chromatic roots in the real and complex numbers, but rather less about their…

Combinatorics · Mathematics 2019-05-31 Peter J. Cameron , Kerri Morgan

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…

Combinatorics · Mathematics 2022-11-10 Jonah Blasiak , Holden Eriksson , Pavlo Pylyavskyy , Isaiah Siegl

We introduce interpolation analogues of Schur Q-functions - the multiparameter Schur Q-functions. We obtain for them several results: a combinatorial formula, generating functions for one-row and two-rows functions, vanishing and…

Combinatorics · Mathematics 2007-05-23 Vladimir N. Ivanov

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

We introduce a new basis for quasisymmetric functions, which arise from a specialization of nonsymmetric Macdonald polynomials to standard bases, also known as Demazure atoms. Our new basis is called the basis of quasisymmetric Schur…

Combinatorics · Mathematics 2010-11-30 J. Haglund , K. Luoto , S. Mason , S. van Willigenburg

Lam and Pylyavskyy introduced loop symmetric functions as a generalization of symmetric functions. They defined loop Schur functions as generating functions over semistandard tableaux with respect to a `colored weight,' and they proved a…

Combinatorics · Mathematics 2018-05-18 Gabriel Frieden

We study the connections between link invariants, the chromatic polynomial, geometric representations of models of statistical mechanics, and their common underlying algebraic structure. We establish a relation between several algebras and…

Combinatorics · Mathematics 2010-09-15 Paul Fendley , Vyacheslav Krushkal

We describe a way to decompose the chromatic symmetric function as a positive sum of smaller pieces. We show that these pieces are $e$-positive for cycles. Then we prove that attaching a cycle to a graph preserves the $e$-positivity of…

Combinatorics · Mathematics 2024-10-30 Foster Tom , Aarush Vailaya

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