In 1976, Wolfgang Haken and Kenneth Appel, two professors at the University of Illinois at Urbana-Champaign, solved one of the most famous problems in mathematics, the “Four Color Problem.” They proved that any two-dimensional map, under natural hypotheses, can be filled in with four colors without any adjacent “countries” sharing the same color.
The article based on their research was published in two parts, “Every planar map is four colorable. Part I: Discharging”, and “Every planar map is four colorable. Part II: Reducibility”, in Volume 21, Number 3 (Fall 1977) of the Illinois Journal of Mathematics and has been one of the most well-known papers ever published in IJM.
To celebrate the 40th anniversary of the paper, we are pleased to announce the upcoming publication of a special volume of invited papers in honor of Professor Haken, scheduled to appear in late 2016 or early 2017 as a regular issue of IJM. In addition to invited contributions, the special volume will also include a biographical article about Haken and a reprint of one of his papers.
Apart from the solution of the Four Color Problem, Wolfgang Haken is known for fundamental contributions to low-dimensional topology, including the solution of the Unknot Problem, the development of theory of normal surfaces, and introducing the notion that came to be known as a Haken manifold. The “Virtual Haken Conjecture,” recently solved by Agol and Wise, has been a major open problem in the study of 3-manifolds for over 40 years and greatly informed the development of the subject.
We would like to give a special thank you to guest editors for the issue, Ilya Kapovich, Christopher Leininger, and Walter Neumann, for their efforts in bringing the issue to fruition.
A special postmark (above) was used by the UI Mathematics Department for several years in the late 1970’s bearing the slogan “Four Colors Suffice,” based on the work by Haken (pictured above seated) and Appel.