Graphs and Combinatorics

, Volume 22, Issue 3, pp 289–295

Coloring Vertices and Faces of Locally Planar Graphs

Authors

    • Department of MathematicsSmith College
  • Bojan Mohar
    • Department of MathematicsUniversity of Ljubljana
    • Department of MathematicsSimon Fraser University
Article

DOI: 10.1007/s00373-006-0653-4

Cite this article as:
Albertson, M. & Mohar, B. Graphs and Combinatorics (2006) 22: 289. doi:10.1007/s00373-006-0653-4

Abstract

If G is an embedded graph, a vertex-face r-coloring is a mapping that assigns a color from the set {1, . . . ,r} to every vertex and every face of G such that different colors are assigned whenever two elements are either adjacent or incident. Let χvf(G) denote the minimum r such that G has a vertex-face r-coloring. Ringel conjectured that if G is planar, then χvf(G)≤6. A graph G drawn on a surface S is said to be 1-embedded in S if every edge crosses at most one other edge. Borodin proved that if G is 1-embedded in the plane, then χ(G)≤6. This result implies Ringel's conjecture. Ringel also stated a Heawood style theorem for 1-embedded graphs. We prove a slight strengthening of this result. If G is 1-embedded in S, let w(G) denote the edge-width of G, i.e. the length of a shortest non-contractible cycle in G. We show that if G is 1-embedded in S and w(G) is large enough, then the list chromatic number ch(G) is at most 8.

Keywords

Vertex face coloring1-embeddedLocally planar
Download to read the full article text

Copyright information

© Springer-Verlag Berlin Heidelberg 2006