A note on adaptable choosability and choosability with separation of planar graphs

Abstract

Let F be a (possibly improper) edge-coloring of a graph G; a vertex coloring of G is adapted to F if no color appears at the same time on an edge and on its two endpoints. If for some integer k, a graph G is such that given any list assignment L to the vertices of G, with |L(v)| ≥ k for all v, and any edge-coloring F of G, G admits a coloring c adapted to F where c(v) ∈ L(v) for all v, then G is said to be adaptably k-choosable. A (k, d)-list assignment for a graph G is a map that assigns to each vertex v a list L(v) of at least k colors such that |L(x) ∩ L(y)| ≤ d whenever x and y are adjacent. A graph is (k, d)-choosable if for every (k, d)-list assignment L there is an L-coloring of G. It has been conjectured that planar graphs are (3, 1)-choosable. We give some progress on this conjecture by giving sufficient conditions for a planar graph to be adaptably 3-choosable. Since (k, 1)-choosability is a special case of adaptable k-choosablity, this implies that a planar graph satisfying these conditions is (3, 1)-choosable.