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University of Cambridge > Talks.cam > Isaac Newton Institute Distinguished Seminars > Maps and graphs on surfaces

## Maps and graphs on surfacesAdd to your list(s) Download to your calendar using vCal - Professor C Thomassen (Technical University of Denmark)
- Thursday 29 May 2008, 17:00-18:00
- Seminar Room 1, Newton Institute.
If you have a question about this talk, please contact Mustapha Amrani. Institute distinguished event Graph coloring is a extensively studied subject, partly because of its relation to optimization (time table problems). One of the main sources of inspiration was the 4 Color Problem (now a theorem). In 1890 Heawood considered the analogue for higher surfaces. This problem, known as the Heawood map color theorem, was settled by Ringel and Youngs in 1968. For example, the number of colors needed in the projective plane and the Klein bottle is 6. For the torus it is 7, etc. Although these numbers tend to infinity, there is a 5 color theorem for each surface in the following sense: For every surface S, there exist a finite number of (forbidden) graphs such that an arbitrary graph on S can be 5-colored if and only if it does not contain one of the forbidden graph as a subgraph. There is no 4-color theorem of this type. In the talk these and related results will be discussed. This talk is part of the Isaac Newton Institute Distinguished Seminars series. ## This talk is included in these lists:- All Talks (aka the CURE list)
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