Graduate Students Seminar

3pm Wednesday 29 October 2003

Chris Wetherell
MSI

Colouring maps and graphs

The Four Colour Problem - the question of whether four colours always suffice to colour any planar map - has a long and turbulent history. In this talk we will look at the concepts of unavoidability and reducibility which led to its eventual proof by Appel and Haken in 1976. The key to discovering a rather more elegant, and moreover humanly verifiable, proof appears to lie in reformulating the problem in different ways, and we will discuss these ideas also.




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