András Hajnal (May 13, 1931 — July 30, 2016)

We are sad to report that András Hajnal, one of the Honorary Presidents of the European Set Theory Society, very unexpectedly died on 30 July 2016 after having a heart attack.

He started his work in axiomatic set theory, in fact he was the first to introduce and study relative constructibility, extending the work of Gödel. However, he is more widely known for his ground breaking work in combinatorial set theory, as one of the founders, in collaboration with Erdős and Rado, of the theory of set mappings and, most of all, the partition calculus. His celebrated joint result with Galvin on cardinal exponentiation initiated Shelah to create PCF theory. He also published more than 30 papers on set theoretic topology and so played an essential role in the introduction of the tools and methods of modern set theory to problems of general topology.

In addition to his work in set theory, he has made significant contributions to finite combinatorics as well. Perhaps the best known of these is the Hajnal–Szemerédi theorem on equitable coloring of graphs that proved a conjecture of Erdős.

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