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The square $G^2$ of a graph $G$ is the graph defined on $V(G)$ such that two vertices $u$ and $v$ are adjacent in $G^2$ if the distance between $u$ and $v$ in $G$ is at most 2. Let $\chi(H)$ and $\chi_{\ell}(H)$ be the chromatic number and…

Combinatorics · Mathematics 2014-05-08 Seog-Jin Kim , Boram Park

An acyclic edge coloring of a graph $G$ is a proper edge coloring such that no bichromatic cycles are produced. The acyclic edge coloring conjecture by Fiam{\v{c}}ik (1978) and Alon, Sudakov and Zaks (2001) states that every simple graph…

Discrete Mathematics · Computer Science 2020-05-14 Qiaojun Shu , Guohui Lin , Eiji Miyano

An \emph{equitable coloring} of a graph is a proper vertex coloring such that the sizes of every two color classes differ by at most 1. Chen, Lih, and Wu conjectured that every connected graph $G$ with maximum degree $\Delta \geq 2$ has an…

Combinatorics · Mathematics 2012-03-05 Keaitsuda Nakprasit , Kittikorn Nakprasit

Let $G$ be a simple graph with $n$ vertices and list chromatic number $\chi_\ell(G)=\chi_\ell$. Suppose that $0\leq t\leq \chi_\ell$ and each vertex of $G$ is assigned a list of $t$ colors. Albertson, Grossman and Haas [1] conjectured that…

Combinatorics · Mathematics 2008-05-22 Moharram Iradmusa

Ramsey's Theorem guarantees for every graph H that any 2-edge-coloring of a sufficiently large complete graph contains a monochromatic copy of H. In 1962, Erdos conjectured that the random 2-edge-coloring minimizes the number of…

Combinatorics · Mathematics 2024-08-22 Daniel Kral , Jan Volec , Fan Wei

The famous List Colouring Conjecture from the 1970s states that for every graph $G$ the chromatic index of $G$ is equal to its list chromatic index. In 1996 in a seminal paper, Kahn proved that the List Colouring Conjecture holds…

Combinatorics · Mathematics 2023-11-09 Marthe Bonamy , Michelle Delcourt , Richard Lang , Luke Postle

Hadwiger's conjecture asserts that every graph without a $K_t$-minor is $(t-1)$-colorable. It is known that the exact version of Hadwiger's conjecture does not extend to list coloring, but it has been conjectured by Kawarabayashi and Mohar…

Combinatorics · Mathematics 2021-10-19 Raphael Steiner

The square $G^2$ of a graph $G$ is the graph defined on $V(G)$ such that two vertices $u$ and $v$ are adjacent in $G^2$ if the distance between $u$ and $v$ in $G$ is at most 2. Let $\chi(H)$ and $\chi_l(H)$ be the chromatic number and the…

Combinatorics · Mathematics 2013-05-17 Seog-Jin Kim , Boram Park

Scott proved in 1997 that for any tree $T$, every graph with bounded clique number which does not contain any subdivision of $T$ as an induced subgraph has bounded chromatic number. Scott also conjectured that the same should hold if $T$ is…

Combinatorics · Mathematics 2022-03-03 Jérémie Chalopin , Louis Esperet , Zhentao Li , Patrice Ossona de Mendez

The Unfriendly Partition Conjecture posits that every countable graph admits a 2-colouring in which for each vertex there are at least as many bichromatic edges containing that vertex as monochromatic ones. This is not known in general, but…

Combinatorics · Mathematics 2023-03-22 John Haslegrave

Let $G$ be a simple graph with maximum degree $\Delta(G)$. A subgraph $H$ of $G$ is overfull if $|E(H)|>\Delta(G)\lfloor |V(H)|/2 \rfloor$. Chetwynd and Hilton in 1985 conjectured that a graph $G$ with $\Delta(G)>|V(G)|/3$ has chromatic…

Combinatorics · Mathematics 2021-07-20 Michael J. Plantholt , Songling Shan

Alon, Krivelevich, and Sudakov conjectured in 1999 that for every finite graph $F$, there exists a quantity $c(F)$ such that $\chi(G) \leq (c(F) + o(1)) \Delta / \log\Delta$ whenever $G$ is an $F$-free graph of maximum degree $\Delta$. The…

Combinatorics · Mathematics 2025-05-13 James Anderson , Anton Bernshteyn , Abhishek Dhawan

List colouring is an influential and classic topic in graph theory. We initiate the study of a natural strengthening of this problem, where instead of one list-colouring, we seek many in parallel. Our explorations have uncovered a…

Combinatorics · Mathematics 2023-08-03 Stijn Cambie , Wouter Cames van Batenburg , Ewan Davies , Ross J. Kang

If $L$ is a list assignment of $r$ colors to each vertex of an $n$-vertex graph $G$, then an equitable $L$-coloring of $G$ is a proper coloring of vertices of $G$ from their lists such that no color is used more than $\lceil n/r\rceil$…

Combinatorics · Mathematics 2023-09-08 H. A. Kierstead , Alexandr Kostochka , Zimu Xiang

A conjecture of Alon, Krivelevich, and Sudakov states that, for any graph $F$, there is a constant $c_F > 0$ such that if $G$ is an $F$-free graph of maximum degree $\Delta$, then $\chi(G) \leq c_F \Delta / \log\Delta$. Alon, Krivelevich,…

Combinatorics · Mathematics 2022-01-25 James Anderson , Anton Bernshteyn , Abhishek Dhawan

The Chen-Lih-Wu Conjecture states that each connected graph with maximum degree $\Delta\geq 3$ that is not the complete graph $K_{\Delta+1}$ or the complete bipartite graph $K_{\Delta,\Delta}$ admits an equitable coloring with $\Delta$…

Combinatorics · Mathematics 2023-11-14 Alexandr Kostochka , Duo Lin , Zimu Xiang

An equitable $k$-coloring of a graph is a proper $k$-coloring where the sizes of any two different color classes differ by at most one. In 1973, Meyer conjectured that every connected graph $G$ has an equitable $k$-coloring for some $k\leq…

Combinatorics · Mathematics 2025-11-07 Yangyang Cheng , Zhenyu Li , Wanting Sun , Guanghui Wang

We consider the problem of coloring the squares of graphs of bounded maximum average degree, that is, the problem of coloring the vertices while ensuring that two vertices that are adjacent or have a common neighbour receive different…

Discrete Mathematics · Computer Science 2013-08-21 Marthe Bonamy , Benjamin Lévêque , Alexandre Pinlou

Let $G$ be a graph on $n$ vertices and let $\mathcal{L}_k$ be an arbitrary function that assigns each vertex in $G$ a list of $k$ colours. Then $G$ is $\mathcal{L}_k$-list colourable if there exists a proper colouring of the vertices of $G$…

Combinatorics · Mathematics 2014-03-12 Jeannette Janssen , Rogers Mathew , Deepak Rajendraprasad

Let G be an n-vertex graph with list-chromatic number $\chi_\ell$. Suppose each vertex of G is assigned a list of t colors. Albertson, Grossman, and Haas conjecture that at least $t n / {\chi_\ell}$ vertices can be colored from these lists.…

Combinatorics · Mathematics 2007-05-23 Glenn G. Chappell
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