# nLab Hans-Joachim Baues

Topologist and author of

amongst others.

A part of his work has developed the ideas of Whitehead's basic programme for algebraic homotopy, using a mix of cofibration categories and categories with a particular type of cylinder functor, that he calls I-categories. These are treated in separate entries.

Baues has also systematically developed aspects of secondary homological algebra (secondary cohomological operations, secondary Steenrod algebra, secondary chain complexes, secondary triangulated category) which is a form of categorification of the usual homological algebra. He has developed them together to give sound applications in the computations with Adams-Novikov spectral sequence and calculations of homotopy groups of spheres.

He is also well known for his development of the “cohomology of small categories” with Wirsching, sometimes called Baues-Wirsching cohomology, although versions of this theory existed prior to his contribution.