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In a seminal paper, Alon and Tarsi have introduced an algebraic technique for proving upper bounds on the choice number of graphs (and thus, in particular, upper bounds on their chromatic number). The upper bound on the choice number of $G$…

Combinatorics · Mathematics 2009-11-12 Dan Hefetz

We define $Z$-signable correspondence assignments on multigraphs, which generalize good correspondence assignments as introduced by Kaul and Mudrock. We introduce an auxiliary digraph that allows us to prove an Alon-Tarsi style theorem for…

Combinatorics · Mathematics 2024-12-19 Ian Gossett

Let $G$ be a connected graph with maximum degree $\Delta$. Brooks' theorem states that $G$ has a $\Delta$-coloring unless $G$ is a complete graph or an odd cycle. A graph $G$ is \emph{degree-choosable} if $G$ can be properly colored from…

Combinatorics · Mathematics 2018-06-19 Daniel W. Cranston , Landon Rabern

A total coloring of a simple undirected graph $G$ is an assignment of colors to its vertices and edges such that the colors given to the vertices form a proper vertex coloring, the colors given to the edges form a proper edge coloring, and…

Discrete Mathematics · Computer Science 2025-08-06 Diptimaya Behera , Mathew C. Francis , Sreejith K. Pallathumadam

Let $G$ be a plane graph with $C$ the boundary of the outer face and let $(L(v):v\in V(G))$ be a family of non-empty sets. By an $L$-coloring of a subgraph $J$ of $G$ we mean a (proper) coloring $\phi$ of $J$ such that $\phi(v)\in L(v)$ for…

Combinatorics · Mathematics 2021-08-31 Luke Postle , Robin Thomas

The dichromatic number of a digraph $D$, denoted by $\vec{\chi}(D)$, is the smallest number of colours required to colour the vertices of $D$ such that each colour class induces an acyclic digraph. A conjecture of Erd\H{o}s and Neumann-Lara…

Combinatorics · Mathematics 2026-04-15 Ararat Harutyunyan , Lucas Picasarri-Arrieta , Gil Puig i Surroca

Recently, Alon introduced the notion of an $H$-code for a graph $H$: a collection of graphs on vertex set $[n]$ is an $H$-code if it contains no two members whose symmetric difference is isomorphic to $H$. Let $D_{H}(n)$ denote the maximum…

Combinatorics · Mathematics 2023-08-22 Patrick Bennett , Emily Heath , Shira Zerbib

We show that if $G$ is a $d$-regular Vizing-class-1 graph, then the proper additive chromatic index of $G$, denoted $\eta'_p(G)$, is equal to its chromatic index. This verifies that a strengthening of the Additive Coloring Conjecture of…

Combinatorics · Mathematics 2026-05-28 Ian Gossett

While solving a question on list coloring of planar graphs, Dvo\v{r}\'{a}k and Postle introduced the new notion of DP-coloring (they called it correspondence coloring). A DP-coloring of a graph $G$ reduces the problem of finding a coloring…

Combinatorics · Mathematics 2018-03-26 Anton Bernshteyn , Alexandr Kostochka , Sergei Pron

DP-coloring is a relatively new coloring concept by Dvo\v{r}\'ak and Postle and was introduced as an extension of list-colorings of (undirected) graphs. It transforms the problem of finding a list-coloring of a given graph $G$ with a…

Combinatorics · Mathematics 2018-12-27 Jørgen Bang-Jensen , Thomas Bellitto , Thomas Schweser , Michael Stiebitz

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

This paper has been withdrawn by the author. Peterson and Woodall previously proved that the list-edge-colouring conjecture holds for graphs without odd cycles of length 5 or longer. D. Peterson and D. R. Woodall, Edge-choosability in…

Combinatorics · Mathematics 2015-08-11 Jessica McDonald

A classical result of Corr\'adi and Hajnal states that every graph $G$ on $n$ vertices with $n\in 3\mathbb{N}$ and $\delta(G) \ge 2n/3$ contains a perfect triangle-tiling, i.e.,\ a spanning set of vertex-disjoint triangles. We explore a…

Combinatorics · Mathematics 2024-08-21 Allan Lo , Ella Williams

We initiate the study of applying the Combinatorial Nullstellensatz to the DP-coloring of graphs even though, as is well-known, the Alon-Tarsi theorem does not apply to DP-coloring. We define the notion of good covers of prime order which…

Combinatorics · Mathematics 2020-08-07 Hemanshu Kaul , Jeffrey A. Mudrock

Let $G$ be an edge-coloured graph. The minimum colour degree $ \delta^c(G) $ of $G$ is the largest integer $k$ such that, for every vertex $v$, there are at least $k$ distinct colours on edges incident to $v$. We say that $G$ is properly…

Combinatorics · Mathematics 2013-12-11 Allan Lo

Let $G$ be a simple planar graph of maximum degree $\Delta$, let $t$ be a positive integer, and let $L$ be an edge list assignment on $G$ with $|L(e)| \geq \Delta+t$ for all $e \in E(G)$. We prove that if $H$ is a subgraph of $G$ that has…

Combinatorics · Mathematics 2018-07-11 Joshua Harrelson , Jessica McDonald , Gregory J. Puleo

We show that, for every $r, k$, there is an $n = n(r,k)$ so that any $r$-coloring of the edges of the complete graph on $[n]$ will yield a monochromatic complete subgraph on vertices ${a + \sum_{i \in I} d_i \mid I \subseteq [k]}$ for some…

Combinatorics · Mathematics 2012-03-01 Andy Parrish

An odd $k$-edge-coloring of a graph $G$ is a (not necessarily proper) edge-coloring with at most $k$ colors such that each non-empty color class induces a graph in which every vertex is of odd degree; similarly, if more than one color per…

Combinatorics · Mathematics 2025-06-26 Xiao-Chuan Liu , Mirko Petruševski , Xu Yang

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

In this paper, we consider coloring of graphs under the assumption that some vertices are already colored. Let $G$ be an $r$-colorable graph and let $P\subset V(G)$. Albertson [J.\ Combin.\ Theory Ser. B \textbf{73} (1998), 189--194] has…

Combinatorics · Mathematics 2013-08-15 Chihoko Ojima , Akira Saito , Kazuki Sano
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