Professor Carsten Thomassen named Honorary Fellow of ICA

The Institute of Combinatorics and its Applications (ICA) is an international scholarly society established for the purpose of promoting the development of combinatorics. ICA’s Honorary Fellowship is given to a person who has made pre-eminent contributions to combinatorics or its applications. ”Dr. Carsten Thomassen is one of the most influential graph theorists of our time,” states the ICA in their press release, where they announced Carsten Thomassen as Honorary Fellow of the ICA.

For a lifetime, Carsten Thomassen has been recognized as one of the internationally leading researchers in his field, the graph theory. He has been awarded and honored for his scientific work before, but the Honorary Fellowship of the ICA makes an impression. “The number of living Honorary Fellows must not exceed ten, so it is a great honor to be part of that company,” says professor Carsten Thomassen about his appointment.

The Thomassen Graph

The graph theory is the mathematical theory of networks, e.g. communication networks, roads, railways, electrical and social networks. Carsten Thomassen has himself found a graph that now bears his name, The Thomassen Graph. “I found the graph that got my name on 29 July 1973 just before we had our first child christened in Aarhus Cathedral. I had been working on the problem for some time, but it was precisely on the 29 July 1973 in the morning that the pieces fell into place,” Carsten Thomassen explains.

The graph Carsten Thomassen found was a "hypotraceable" graph. A graph is called "hypotraceable" if it does not have a path through all points, but if you remove any point (not just a well-chosen point) then there is a path through all points. The definition is similar to that of a "hypohamiltonian" graph. A graph is called "hypohamiltonian" if it does not have a circuit through all points, but if you remove any point (not just a well-chosen point), then there is a circuit through all points. In 1973, we knew infinitely many such hypohamiltonian graphs, but in 1973 it was unresolved that there was a hypotraceable graph at all. Until Carsten Thomassen found one with 34 points! And this is just one of Carsten Thomassen’s contributions to our understanding of graphs.