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We introduce the partition function of edge-colored graph homomorphisms, of which the usual partition function of graph homomorphisms is a specialization, and present an efficient algorithm to approximate it in a certain domain. Corollaries…

Combinatorics · Mathematics 2015-05-05 Alexander Barvinok , Pablo Soberón

We define a new type of vertex coloring which generalizes vertex coloring in graphs, hypergraphs, and simplicial complexes. This coloring also generalizes oriented coloring, acyclic coloring, and star coloring. There is an associated…

Combinatorics · Mathematics 2020-01-22 John Machacek

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

The chromatic polynomial $\pi_{G}(k)$ of a graph $G$ can be viewed as counting the number of vertices in a family of coloring graphs $\mathcal C_k(G)$ associated with (proper) $k$-colorings of $G$ as a function of the number of colors $k$.…

Combinatorics · Mathematics 2025-05-06 Shamil Asgarli , Sara Krehbiel , Howard W. Levinson , Heather M. Russell

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

Let $G$ be a finite group and $\chi: G \rightarrow \mathbb{C}$ a class function. Let $H = (V,E)$ be a directed graph with for each vertex a cyclic order of the edges incident to it. The cyclic orders give a collection $F$ of faces of $H$.…

Combinatorics · Mathematics 2018-09-11 Bart Litjens , Bart Sevenster

In [J. Combin. Theory Ser. B 161 (2023), 109--119], the authors showed that the list-color function $P_l(G,k)$ of any simple graph $G$ of size $m$ coincides with its chromatic polynomial $P(G,k)$ for all integers $k\ge m-1$. In this…

Combinatorics · Mathematics 2024-12-11 Fengming Dong , Meiqiao Zhang

Stanley's symmetrized chromatic polynomial is a generalization of the ordinary chromatic polynomial to a graph invariant with values in a ring of polynomials in infnitely many variables. The ordinary chromatic polynomial is a specialization…

Combinatorics · Mathematics 2018-09-11 Marina Dudina , Vyacheslav Zhukov

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…

Combinatorics · Mathematics 2025-03-26 Foster Tom , Aarush Vailaya

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

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

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…

Combinatorics · Mathematics 2024-07-09 Bruce E. Sagan , Foster Tom

The Stanley-Stembridge conjecture asserts that the chromatic symmetric function of a $(3+1)$-free graph is $e$-positive. Recently, Hikita proved this conjecture by giving an explicit $e$-expansion of the Shareshian-Wachs $q$-chromatic…

Combinatorics · Mathematics 2025-04-10 Sean T. Griffin , Anton Mellit , Marino Romero , Kevin Weigl , Joshua Jeishing Wen

We give a probabilistic interpretation of the coefficients of the elementary symmetric function expansion of the chromatic quasisymmetric function for any unit interval graph. As a corollary, we prove the Stanley--Stembridge conjecture.

Combinatorics · Mathematics 2025-12-29 Tatsuyuki Hikita

The $k$th power $G^k$ of a graph $G$ is the graph defined on $V(G)$ such that two vertices $u$ and $v$ are adjacent in $G^k$ if the distance between $u$ and $v$ in $G$ is at most $k$. Let $\chi(H)$ and $\chi_l(H)$ be the chromatic number…

Combinatorics · Mathematics 2013-09-05 Seog-Jin Kim , Young Soo Kwon , Boram Park

The Kromatic symmetric function (KSF) $\overline{X}_G$ of a graph $G$ is a $K$-analogue introduced by Crew, Pechenik, and Spirkl in arXiv:2301.02177 of Stanley's chromatic symmetric function (CSF) $X_G$. The KSF is known to distinguish some…

Combinatorics · Mathematics 2025-10-03 Laura Pierson , Soham Samanta

Stanley introduced the concept of chromatic symmetric functions of graphs which extends and refines the notion of chromatic polynomials of graphs, and asked whether trees are determined up to isomorphism by their chromatic symmetric…

Combinatorics · Mathematics 2024-02-21 Yuzhenni Wang , Xingxing Yu , Xiao-Dong Zhang

We introduce a notion of color-criticality in the context of chromatic-choosability. We define a graph $G$ to be strong $k$-chromatic-choosable if $\chi(G) = k$ and every $(k-1)$-assignment for which $G$ is not list-colorable has the…

Combinatorics · Mathematics 2018-08-08 Hemanshu Kaul , Jeffrey A. Mudrock

In this paper we describe all edge-colored graphs that are fully symmetric with respect to colors and transitive on every set of edges of the same color. They correspond to fully symmetric homogeneous factorizations of complete graphs. Our…

Combinatorics · Mathematics 2012-01-24 Mariusz Grech , Andrzej Kisielewicz

A graph $H$ is said to be common if the number of monochromatic labelled copies of $H$ in a red/blue edge colouring of a large complete graph is asymptotically minimized by a random colouring with an equal proportion of each colour. We…

Combinatorics · Mathematics 2025-09-16 Natalie Behague , Natasha Morrison , Jonathan A. Noel