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We restate theorems of Hutchinson on list-colouring extendability for outerplanar graphs in terms of non-vanishing monomials in a graph polynomial, which yields an Alon-Tarsi equivalent for her work. This allows to simplify her proofs as…

组合数学 · 数学 2020-08-11 Przemysław Gordinowicz , Paweł Twardowski

A celebrated result of Thomassen states that not only can every planar graph be colored properly with five colors, but no matter how arbitrary palettes of five colors are assigned to vertices, one can choose a color from the corresponding…

组合数学 · 数学 2013-05-10 Maria Axenovich , Joan P. Hutchinson , Michelle A. Lastrina

Thomassen in 1994 published a famous proof of the fact that the choosability of a planar graph is at most 5. Zhu in 2019 generalized this result by showing that the same bound holds for Alon-Tarsi numbers of planar graphs. We present an…

组合数学 · 数学 2023-03-07 Jakub Kozik , Bartosz Podkanowicz

As one of the first applications of the polynomial method in combinatorics, Alon and Tarsi gave a way to prove that a graph is choosable (colorable from any lists of prescribed size). We describe an efficient way to implement this approach,…

离散数学 · 计算机科学 2023-01-18 Zdeněk Dvořák

In this article, we use a unified approach to prove several classes of planar graphs are DP-$3$-colorable, which extend the corresponding results on $3$-choosability.

组合数学 · 数学 2018-09-20 Runrun Liu , Sarah Loeb , Yuxue Yin , Gexin Yu

This paper proves that the Alon-Tarsi number of any planar graph is at most $5$, which gives an alternate proof of the $5$-choosability as well as the $5$-paintability of planar graphs.

组合数学 · 数学 2017-11-30 Xuding Zhu

Thomassen conjectured that triangle-free planar graphs have an exponential number of $3$-colorings. We show this conjecture to be equivalent to the following statement: there exists a positive real $\alpha$ such that whenever $G$ is a…

组合数学 · 数学 2017-09-20 Zdeněk Dvořák , Jean-Sébastien Sereni

We generalize a parity result of Fleishner and Stiebitz that being combined with Alon--Tarsi polynomial method allowed them to prove that a 4-regular graph formed by a Hamiltonian cycle and several disjoint triangles is always 3-choosable.…

组合数学 · 数学 2015-12-22 Fedor V. Petrov

A graph G is k-choosable if G can be properly colored whenever every vertex has a list of at least k available colors. Thomassen's theorem states that every planar graph is 5-choosable. We extend the result by showing that every graph with…

组合数学 · 数学 2018-10-26 Zdeněk Dvořák , Bernard Lidický , Riste Škrekovski

The Gr\"{o}tzsch Theorem states that every triangle-free planar graph admits a proper $3$-coloring. Among many of its generalizations, the one of Gr\"{u}nbaum and Aksenov, giving $3$-colorability of planar graphs with at most three…

组合数学 · 数学 2022-07-13 Hoang La , Borut Lužar , Kenny Štorgel

Thomassen conjectured that every triangle-free planar graph on n vertices has exponentially many 3-colorings, and proved that it has at least 2^[n^(1/12)/20000] distinct 3-colorings. We show that it has at least 2^sqrt(n/362) distinct…

组合数学 · 数学 2011-03-31 Arash Asadi , Zdenek Dvorak , Luke Postle , Robin Thomas

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…

组合数学 · 数学 2012-05-28 Z. Dvorak

Let $G$ be a planar embedding with list-assignment $L$ and outer cycle $C$, and let $P$ be a path of length at most four on $C$, where each vertex of $G\setminus C$ has a list of size at least five and each vertex of $C\setminus P$ has a…

组合数学 · 数学 2024-03-21 Joshua Nevin

We first give an alternative proof of the Alon-Tarsi list coloring theorem. We use the ideas from this proof to obtain the following result, which is an additive coloring analog of the Alon-Tarsi Theorem: Let $G$ be a graph and let $D$ be…

组合数学 · 数学 2024-07-15 Ian Gossett

Grotzsch proved that every triangle-free planar graph is 3-colorable. Thomassen proved that every planar graph of girth at least five is 3-choosable. As for other surfaces, Thomassen proved that there are only finitely many 4-critical…

组合数学 · 数学 2017-10-20 Luke Postle

This paper constructs a planar graph $G_1$ such that for any subgraph $H$ of $G_1$ with maximum degree $\Delta(H) \le 3$, $G_1-E(H)$ is not $3$-choosable, and a planar graph $G_2$ such that for any star forest $F$ in $G_2$, $G_2-E(F)$…

组合数学 · 数学 2019-06-05 Ringi Kim , Seog-Jin Kim , Xuding Zhu

Let $G$ be a planar embedding with list-assignment $L$ and outer cycle $C$, and let $P$ be a path of length at most four on $C$, where each vertex of $G\setminus C$ has a list of size at least five and each vertex of $C\setminus P$ has a…

组合数学 · 数学 2022-12-21 Joshua Nevin

Thomassen conjectured that triangle-free planar graphs have exponentially many 3-colorings. Recently, he disproved his conjecture by providing examples of such graphs with $n$ vertices and at most $2^{15n/\log_2 n}$ 3-colorings. We improve…

组合数学 · 数学 2021-08-31 Zdeněk Dvořák , Luke Postle

In 1994, Thomassen famously proved that every planar graph is 5-choosable, resolving a conjecture initially posed by Vizing and, independently, Erd\H{os}, Rubin, and Taylor in the 1970s. Later, Thomassen proved that every planar graph of…

组合数学 · 数学 2022-12-12 Luke Postle , Evelyne Smith-Roberge

There exists a variety of coloring problems for plane graphs, involving vertices, edges, and faces in all possible combinations. For instance, in the \emph{entire coloring} of a plane graph we are to color these three sets so that any pair…

组合数学 · 数学 2020-04-07 Jarosław Grytczuk , Stanislav Jendrol' , Mariusz Zając
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