English

Every toroidal graph without triangles adjacent to $5$-cycles is DP-$4$-colorable

Combinatorics 2019-08-15 v2 Discrete Mathematics

Abstract

DP-coloring, also known as correspondence coloring, is introduced by Dvo{\v{r}}{\'{a}}k and Postle. It is a generalization of list coloring. In this paper, we show that every connected toroidal graph without triangles adjacent to 55-cycles has minimum degree at most three unless it is a 2-connected 44-regular graph with Euler characteristic ϵ(G)=0\epsilon(G) = 0. Consequently, every toroidal graph without triangles adjacent to 55-cycles is DP-44-colorable. In the final, we show that every planar graph without two certain subgraphs is DP-44-colorable. As immediate consequences, (i) every planar graph without 33-cycles adjacent to 44-cycles is DP-44-colorable; (ii) every planar graph without 33-cycles adjacent to 55-cycles is DP-44-colorable; (iii) every planar graph without 44-cycles adjacent to 55-cycles is DP-44-colorable.

Keywords

Cite

@article{arxiv.1803.01197,
  title  = {Every toroidal graph without triangles adjacent to $5$-cycles is DP-$4$-colorable},
  author = {Tao Wang},
  journal= {arXiv preprint arXiv:1803.01197},
  year   = {2019}
}

Comments

All the results are improved and merged into arXiv:1907.07141

R2 v1 2026-06-23T00:40:56.096Z