Abstract | ||
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Let M be a map on a closed surface F2 and suppose that each country of the map has at most r disjoint connected regions. Such a map is called an r-pire map on F2. In 1890, Heawood proved that the countries of M can be properly colored with ⌊(6r+1+(6r+1)2−24ε)/2⌋ colors, where ε is the Euler characteristic of F2. Also, he conjectured that this is best possible except for the case (ε,r)=(2,1), and now it is proved for all cases where ε≥0 and some cases where ε<0. |
Year | DOI | Venue |
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2013 | 10.1016/j.disc.2012.10.024 | Discrete Mathematics |
Keywords | DocType | Volume |
Empire problem,Even embedding,Current graph | Journal | 313 |
Issue | ISSN | Citations |
19 | 0012-365X | 0 |
PageRank | References | Authors |
0.34 | 5 | 1 |
Name | Order | Citations | PageRank |
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Kenta Noguchi | 1 | 0 | 0.68 |