Zoltán Ésik (1951 - 2016) - In Memoriam

Our friend and colleague Zoltán Ésik passed away in Reykjavik, Iceland, on Wednesday, 25 May 2016. He was visiting us as he did with some regularity, compatibly with his many engagements throughout the world. The day before his untimely death, Zoltán had delivered an ICE-TCS seminar entitled Equational Logic of Fixed Point Operations at Reykjavik University. At the start of his talk, he looked somewhat tired and out of breath. However, the more he was presenting a research topic that he loved and that has kept him busy for most of his research career, the more he seemed to be feeling at ease. After the talk, we spent some time making plans for mutual visits in the autumn of 2016 and we discussed some EATCS-related matters. His wife Zsuzsa and he were due to spend a few days travelling in the north of Iceland before their return to Szeged, but life had other ideas. Zoltán was a scientist of the highest calibre and has left behind a large body of deep and seminal work that will keep researchers in theoretical computer science busy for a long time to come. The list of refereed publications available from his web site at http://www.inf.u-szeged.hu/~ze/classified.pdf includes two books, 32 edited volumes, 135 journal papers, four book chapters, 86 conference papers and seven papers in other edited volumes. However, impressive as they undoubtedly are, these numbers give only a very partial picture of Zoltán’s scientific stature. Together with the late Stephen Bloom, Zoltán was the prime mover in the monumental development of Iteration Theories. As Stephen and Zoltán wrote in the preface of their massive book on the topic, which was published in 1993 by Springer: