Hansjoachim Walther (16 December 1939 – 17 January 2005) was a German mathematician and politician. He served as a professor of mathematics at the Technische Universität Ilmenau, made contributions to graph theory, and later entered politics during the Peaceful Revolution, becoming a leading figure in the German Social Union (DSU) and serving briefly as a Federal Minister for Special Affairs in the third cabinet of Helmut Kohl following German reunification.
Early life and education
Walther was born on 16 December 1939 in Bütow, Farther Pomerania (now Bytów, Poland), to Joachim Walther and Erika Dobat, both civil servants. His family fled to Zeitz in 1945. In East Germany, he completed an apprenticeship as a Spitzendreher (a metalworking profession) before studying mathematics at the Dresden University of Technology. He graduated as a Diplom-Mathematiker in 1964.
Academic career
Walther earned his doctorate (Dr. rer. nat.) in 1966 at the Technische Universität Ilmenau with a dissertation on the existence of Hamiltonian cycles in planar regular graphs. He completed his habilitation in 1969 and was appointed associate professor at the Technische Universität Ilmenau in 1986, where he remained until his death.
He published approximately 66 academic works, including six books. His research focused on graph theory, particularly Hamiltonian cycles, polyhedral graphs, shortness exponents, and chromatic numbers of distance graphs. Notable works include Ten Applications of Graph Theory (1985) and Graphen, Algorithmen, Programme (1987). Among his most cited publications is the 1973 paper "Shortness exponents of families of graphs," co-authored with Branko Grünbaum.
The Walther graph is named after him – a specific graph used as a counterexample in Hamiltonian graph theory.
Political career
East Germany (1989–1990)
During the Peaceful Revolution, Walther co-founded the Forum Party of Thuringia in 1989. In January 1990, he co-founded the German Social Union (DSU), a right-wing party modelled after the Bavarian CSU, and became its deputy chairman. In the March 1990 Volkskammer election, he served as the DSU's lead candidate and was elected to the Volkskammer for Suhl. The DSU, as part of the Alliance for Germany, entered the government of Lothar de Maizière. Walther became chairman of the DSU parliamentary group.
In May 1990, Walther was elected national chairman of the DSU, succeeding Hans-Wilhelm Ebeling. His leadership pushed the party further to the right, leading to the departure of several prominent members. The DSU under Walther advocated for immediate German reunification.
Federal Republic of Germany (1990–2005)
Following German reunification on 3 October 1990, Walther was one of 144 Volkskammer members co-opted into the Bundestag. He was appointed Minister for Special Affairs in the third Kohl cabinet, a position he held until 18 January 1991.
In the 1990 federal election, the DSU failed to pass the five-percent threshold, receiving only approximately one percent of the vote in the new states and 0.19 percent nationwide. After the election, the DSU quickly declined. Walther left the DSU and joined the Christian Democratic Union (CDU) in 1993, for which he was later elected to the Ilm-Kreis district council.
Personal life and death
Walther died of a heart attack on 17 January 2005 while playing football in Stützerbach near Ilmenau. He was 65 years old.
