ArticleOriginal scientific text
Title
Colouring vertices of plane graphs under restrictions given by faces
Authors 1, 1
Affiliations
- Institute of Mathematics, P.J. Šafárik University, Jesenná 5, SK-04001 Košice, Slovakia
Abstract
We consider a vertex colouring of a connected plane graph G. A colour c is used k times by a face α of G if it appears k times along the facial walk of α. We prove that every connected plane graph with minimum face degree at least 3 has a vertex colouring with four colours such that every face uses some colour an odd number of times. We conjecture that such a colouring can be done using three colours. We prove that this conjecture is true for 2-connected cubic plane graphs. Next we consider other three kinds of colourings that require stronger restrictions.
Keywords
vertex colouring, plane graph, weak parity vertex colouring, strong parity vertex colouring, proper colouring, Lebesgue theorem
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