The planar and toroidal graphs without intersecting triangles DP-4-degeneracy conjecture

Let GG be a planar or toroidal graph without intersecting triangles. Let (H,f)(H,f) be a cover of GG, where ff assigns to each vertex of HH a value in {0,1,2}\{0,1,2\}. A strictly ff-degenerate transversal is a transversal of HH inducing, in every nonempty subgraph, a vertex whose degree is less than its assigned ff-value. The planar and toroidal graphs without intersecting triangles conjecture. If

f(v,1)+f(v,2)++f(v,κ)4f(v,1)+f(v,2)+\dots+f(v,\kappa)\geq 4

for each vV(G)v\in V(G), then HH has a strictly ff-degenerate transversal. This conjecture extends established DP-colouring, list-colouring, and vertex-arboricity results for planar and toroidal graphs without intersecting triangles; the full cover statement remains open.

Sources & referencesView supporting material

Primary source

Fangyao Lu, Qianqian Wang and Tao Wang, “Cover and variable degeneracy”, arXiv:1907.06630 (2021).

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