Wolfgang Haken
1928–2022, Berlin, Germany, Champaign, Illinois, United States
German-American mathematician who co-proved the four colour theorem with Kenneth Appel (1976) and founded the theory of Haken manifolds in low-dimensional topology.
Wolfgang Haken was born in Berlin; his father was a physicist who had studied under Max Planck. Drafted into an anti-aircraft unit at fifteen during the Second World War, he later worked as a farmhand before returning to study mathematics and physics at the University of Kiel, earning his PhD in 1953 under Karl-Heinrich Weise. He then worked for a decade as an electrical engineer at Siemens in Munich, pursuing topology research in his spare time.
In 1961 Haken published an algorithm solving the unknotting problem — deciding whether a given knot diagram is the trivial knot — building a theory of normal surfaces in 3-manifolds that brought him international recognition. He introduced what are now called Haken manifolds, a class of 3-manifolds containing an incompressible surface, and showed that such manifolds can be cut down to simple pieces along a finite hierarchy of surfaces; this work underlies much of algorithmic 3-manifold topology and motivated the later virtually Haken conjecture, proved by Ian Agol.
Invited to the University of Illinois at Urbana-Champaign in 1962, Haken joined the faculty permanently and, with Kenneth Appel, spent years reducing the four colour conjecture to 1,936 unavoidable configurations checked by computer in 1976 — sharing the 1979 Fulkerson Prize for the result. He became a U.S. citizen in 1976, retired from Illinois in 1998, and died in Champaign in 2022.
Workplaces: Siemens, Munich, University of Illinois at Urbana-Champaign
Germany, United States