Coloring even-faced graphs in the torus and the Klein bottle

نویسندگان

  • Daniel Král
  • Robin Thomas
چکیده

We prove that a triangle-free graph drawn in the torus with all faces bounded by even walks is 3-colorable if and only if it has no subgraph isomorphic to the Cayley graph C(Z13;1,5). We also prove that a non-bipartite quadrangulation of the Klein bottle is 3colorable if and only if it has no non-contractible separating cycle of length at most four and no odd walk homotopic to a non-contractible two-sided simple closed curve. These results settle a conjecture of Thomassen and two conjectures of Archdeacon, Hutchinson, Nakamoto, Negami and Ota.

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عنوان ژورنال:
  • Combinatorica

دوره 28  شماره 

صفحات  -

تاریخ انتشار 2008