Wolfgang Haken
Wolfgang Haken (born
June 21,
1928) is a
mathematician who specializes in
topology, in particular
3-manifolds.
In 1976 together with colleague
Kenneth Appel at the
University of Illinois at Urbana-Champaign, Haken solved one of the most famous problems in mathematics, the
four-color theorem. They proved that any two-dimensional map, with certain limitations, can be filled in with four colors without any adjacent "countries" sharing the same color.
Haken has introduced several important ideas, including
Haken manifolds,
Kneser-Haken finiteness, and an expansion of the work of
Kneser into a theory of
normal surfaces. Much of his work has an algorithmic aspect, and he is one of the influential figures in
algorithmic topology. One of his key contributions to this field is an algorithm to detect if a knot is unknotted.
*
Unknotting problem* Haken, W. "Theorie der Normalflachen."
Acta Math. 105, 245-375, 1961.
