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JOURNALS // Zapiski Nauchnykh Seminarov POMI // Archive

Zap. Nauchn. Sem. POMI, 2014 Volume 427, Pages 74–88 (Mi znsl6044)

On Heawood-type problem for maps with tangencies

G. V. Nenashev

Department of Mathematics, Stockholm University, SE-106 91 Stockholm, Sweden

Abstract: The class of maps on a surface of genus $g>0$ such that each point belongs to at most $k\geq3$ regions is studied. We study chromatic numbers of such maps (regions having a common point must have distinct colors) in dependence on $g$ and $k$.
In general case, upper bounds on these chromatic numbers are proved. In case $k=4$, it is proved that the problem described above is equivalent to the problem of finding the maximal chromatic number for analogues of $1$-planar graphs on a surface of genus $g$. In this case a more strong bound than in general case is obtained and a method of constructing examples which confirm accuracy of our bound is presented.
An upper bound on maximal chromatic number for analogues of $2$-planar graphs on a surface of genus $g$ is proved.

Key words and phrases: graph embedding, map, surface, chromatic number, $1$-planar graph, topological graph.

UDC: 519.173.2+519.174.7

Received: 10.11.2014


 English version:
Journal of Mathematical Sciences (New York), 2016, 212:6, 688–697

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© Steklov Math. Inst. of RAS, 2024