Results 181 to 190 of about 1,408,918 (247)

Explicit 3‐colorings for Exponential Graphs

open access: yesJournal of Graph Theory, EarlyView.
ABSTRACT In 1985, El‐Zahar and Sauer showed that the chromatic number of the direct product of two 4‐chromatic graphs is 4, establishing a nontrivial case of Hedetniemi's conjecture, which has since been refuted in general. Their proof uses the concept of an exponential graph, showing that if a graph H $H$ has no proper 3‐coloring, then the exponential
Adrien Argento   +2 more
wiley   +1 more source

Flexible List Coloring of Graphs With Maximum Average Degree Less Than 3

open access: yesJournal of Graph Theory, EarlyView.
ABSTRACT In the flexible list coloring problem, we consider a graph G $G$ and a color list assignment L $L$ on G $G$, as well as a subset U ⊆ V ( G ) $U\subseteq V(G)$ for which each u ∈ U $u\in U$ has a preferred color p ( u ) ∈ L ( u ) $p(u)\in L(u)$. Our goal is to find a proper L $L$‐coloring ϕ $\phi $ of G $G$ such that ϕ ( u ) = p ( u ) $\phi (u)=
Richard Bi, Peter Bradshaw
wiley   +1 more source

Sparse Graphs With Local Covering Conditions on Edges

open access: yesJournal of Graph Theory, EarlyView.
ABSTRACT In 1988, Erdős suggested the question of minimizing the number of edges in a connected n $n$‐vertex graph where every edge is contained in a triangle. Shortly after, Catlin, Grossman, Hobbs, and Lai resolved this in a stronger form. In this paper, we study a natural generalization of the question of Erdős in which we replace “triangle” with ...
Debsoumya Chakraborti   +3 more
wiley   +1 more source

Path Degeneracy and Applications

open access: yesJournal of Graph Theory, EarlyView.
ABSTRACT In this work, we relate girth and path‐degeneracy in classes with sub‐exponential expansion, with explicit bounds for classes with polynomial expansion and proper minor‐closed classes that are tight up to a constant factor (and tight up to second order terms if a classical conjecture on existence of g $g$‐cages is verified). As an application,
Yuquan Lin, Patrice Ossona de Mendez
wiley   +1 more source

Abelian varieties of prescribed order over finite fields. [PDF]

open access: yesMath Ann
van Bommel R   +4 more
europepmc   +1 more source

On Sparsity Conditions Guaranteeing a Fractional Coloring

open access: yesJournal of Graph Theory, EarlyView.
ABSTRACT A graph has an ( a : b ) $(a:b)$ ‐coloring if there exists an assignment from the vertices to subsets of { 1 , … , a } $\{1,\ldots ,a\}$ with size b $b$ such that adjacent vertices are assigned disjoint subsets. Odd girth at least 2 k + 1 $2k+1$ is a necessary condition for a graph to have a ( 2 k + 1 : k ) $(2k+1:k)$‐coloring.
Ilkyoo Choi
wiley   +1 more source

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