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Gy\'arf\'as famously showed that in every $r$-coloring of the edges of the complete graph $K_n$, there is a monochromatic connected component with at least $\frac{n}{r-1}$ vertices. A recent line of study by Conlon, Tyomkyn, and the second…

Combinatorics · Mathematics 2023-12-27 Lyuben Lichev , Sammy Luo

A $t$-tone coloring of a graph $G$ assigns to each vertex a set of $t$ colors such that any pair of vertices $u, v$ with distance $d$ can share at most $d-1$ colors. In this note, we prove several new results on $t$-tone coloring. For…

Combinatorics · Mathematics 2025-10-16 Patrick Bennett , Jade Nichols

Let $G$ be a graph and c a proper k-coloring of G, i.e. any two adjacent vertices u and v have different colors c(u) and c(v). A proper k-coloring is a b-coloring if there exists a vertex in every color class that contains all the colors in…

Combinatorics · Mathematics 2023-11-23 Magda Dettlaff , Hanna Furmańczyk , Iztok Peterin , Riana Roux , Radosław Ziemann

Thomassen formulated the following conjecture: Every $3$-connected cubic graph has a red-blue vertex coloring such that the blue subgraph has maximum degree $1$ (that is, it consists of a matching and some isolated vertices) and the red…

Combinatorics · Mathematics 2019-02-01 János Barát

This paper studies edge-precoloring extensions in Cartesian products of graphs, motivated by a conjecture of Casselgren, Petros, and Fufa. We formulate a general hypothesis stating that if every edge-precoloring of $G$ and $H$ of sizes…

Combinatorics · Mathematics 2026-04-07 Pál Bärnkopf , Ervin Győri

For a graph $G$ with a list assignment $L$ and two $L$-colorings $\alpha$ and $\beta$, an $L$-recoloring sequence from $\alpha$ to $\beta$ is a sequence of proper $L$-colorings where consecutive colorings differ at exactly one vertex. We…

Combinatorics · Mathematics 2025-10-21 Chenran Pan , Weifan Wang , Runrun Liu

A vertex coloring of a graph $G$ is called a 2-distance coloring if any two vertices at distance at most $2$ from each other receive different colors. Let $G$ be a planar graph with girth at least $5$. We prove that $G$ admits a…

Combinatorics · Mathematics 2023-11-07 Zakir Deniz

We consider two possible extensions of a theorem of Thomassen characterizing the graphs admitting a 2-vertex-connected orientation. First, we show that the problem of deciding whether a mixed graph has a 2-vertex-connected orientation is…

Combinatorics · Mathematics 2022-03-02 Florian Hörsch , Zoltán Szigeti

We say a proper coloring of a graph is distance-$k$ fall if every vertex is within distance $k$ of at least one vertex of every color. We show that if $G$ is a connected graph of order at least $3$ that is $3$-colorable, thenit has a…

Combinatorics · Mathematics 2025-09-01 Wayne Goddard , Sonwabile Mafunda

We consider the problem of extending partial edge colorings of cartesian products of graphs. More specifically, we suggest the following Evans-type conjecture: If $G$ is a graph where every precoloring of at most $k$ precolored edges can be…

Combinatorics · Mathematics 2023-03-10 Carl Johan Casselgren , Fikre B. Petros , Samuel A. Fufa

We prove that if $H$ is a subgraph of a complete multipartite graph $G$, then $H$ contains a connected component $H'$ satisfying $|E(H')||E(G)|\geq |E(H)|^2$. We use this to prove that every three-coloring of the edges of a complete graph…

Combinatorics · Mathematics 2022-08-30 Sammy Luo

The aim of this paper is to generalize the notion of the coloring complex of a graph to hypergraphs. We present three different interpretations of those complexes -- a purely combinatorial one and two geometric ones. It is shown, that most…

Combinatorics · Mathematics 2012-05-01 Felix Breuer , Aaron Dall , Martina Kubitzke

We construct an infinite family of counterexamples to Thomassen's conjecture that the vertices of every 3-connected, cubic graph on at least 8 vertices can be colored blue and red such that the blue subgraph has maximum degree at most 1 and…

Combinatorics · Mathematics 2019-08-20 Thomas Bellitto , Tereza Klimošová , Martin Merker , Marcin Witkowski , Yelena Yuditsky

An injective coloring of a graph $G$ is an assignment of colors to the vertices of $G$ so that any two vertices with a common neighbor have distinct colors. A graph $G$ is injectively $k$-choosable if for any list assignment $L$, where…

We classify the countable homogeneous coloured multipartite graphs with any finite number of parts. By Fraisse's Theorem this amounts to classifying the families F of pairwise non-embeddable finite coloured multipartite graphs for which the…

Combinatorics · Mathematics 2014-06-26 Deborah C Lockett , John K Truss

We correct some errors and omissions primarily in a paper [Albertson&Hutchinson2004], discovered by R.B. Richter, and also some in a proof of [Thomassen1993] and of [Yu1997]. We give a short proof of Thomassen's theorem that every…

Combinatorics · Mathematics 2016-05-10 M. O. Albertson , J. P. Hutchinson , R. B. Richter

DP-coloring (also known as correspondence coloring) is a generalization of list coloring introduced recently by Dvo\v{r}\'ak and Postle (2017). In this paper, we prove that every planar graph $G$ without $4$-cycles adjacent to $k$-cycles is…

Combinatorics · Mathematics 2018-11-08 Lily Chen , Runrun Liu , Gexin Yu , Ren Zhao , Xiangqian Zhou

A graph is k-choosable if it can be colored whenever every vertex has a list of at least k available colors. We prove that if cycles of length at most four in a planar graph G are pairwise far apart, then G is 3-choosable. This is analogous…

Combinatorics · Mathematics 2012-05-28 Z. Dvorak

A list assignment $L$ for a graph $G$ is an $(\ell,k)$-list assignment if $|L(v)|\geq \ell$ for each $v \in V(G)$ and $|L(u) \cap L(v)| \leq k$ for each $uv \in E(G)$. We say $G$ is $(\ell,k)$-choosable if it admits an $L$-colouring for…

Combinatorics · Mathematics 2022-03-30 Evelyne Smith-Roberge

A graph $G$ is $(a,b)$-choosable if for any color list of size $a$ associated with each vertices, one can choose a subset of $b$ colors such that adjacent vertices are colored with disjoint color sets. This paper shows an equivalence…

Discrete Mathematics · Computer Science 2010-06-16 Yves Aubry , Godin Jean-Christophe , Togni Olivier