### Encounter 20

#### Prof. Karl Sigmund

**Profession - **Mathematiker

- Title
- Ohne Titel
- Date
- 1985
- Measures
- 167 X 86

Playing mind games with the laws and functions of mathematics – from geometry and algebra to infinitesimal and vector calculus – was one of those intellectual exercises that used to give OUBEY a great deal of pleasure. One of his assignments as architecture student was to design a piece of furniture and he chose to design a folding chair. Only with his passion for such intellectual exercises, he became so involved in the mathematical side of the project that in the end what he presented was not so much the design for a foldable chair as the model of a special rotation vector he’d developed. So much for the moment about OUBEY and mathematics.

In Professor Karl Sigmund I found a mathematician who not only has an international standing in his chosen field but whose research in this field is focused on those mathematical issues that were of such passionate interest to OUBEY. Like investigation of the long-term behavior of complex dynamic systems using the metric measurements and probability theorem methods of that branch of mathematics known as ergodic theory. Interestingly enough, the roots of this particular discipline lie in celestial mechanics. But it also deals with the mathematical side of biology (ecology, population genetics) and chemical kinetics and also with evolutionary game theory, a field pioneered by Professor Sigmund himself, a mathematician who was prepared to wager the experiment of being taped in a live encounter with a completely unknown painting by an artist he’d never heard of.

Professor Sigmund is a member of the Mathematics Natural Sciences class of the Austrian Academy of Sciences and a member of the Leopoldina, the national academy of Germany since 2003. In 2006, a readers’ poll of the Austrian daily Die Presse and the ORF voted him Austrian of the Year in the Research category.

Karl Sigmund’s interests include not just mathematics but the history of mathematics as well. He has organized exhibitions about the emigration of Austrian mathematicians in 1938 and about Kurt Gödel, one of the greatest mathematicians of the twentieth century. In what is known as Gödel’s ontological proof – a formal argument for the existence of God – Gödel, who was a great admirer of Leibniz, developed his own theory of monads. And so, if you like, this closes a small circle in the OUBEY Encounter Project as OUBEY dedicated one of his paintings to Leibniz’s Monadology, giving it the title Die Reise der Monaden (The Journey of the Monads).

When Professor Sigmund arrived for the encounter in a seminar room at the Institute of Mathematics at the University of Vienna, it was late afternoon on 15 September 2011 and he’d already had a long and tiring day behind him. He told me he wasn’t really feeling fresh enough for such an experiment. Fortunately though he agreed to go ahead with it and so, when it was finished, he was astonished that he then felt as invigorated and lively as though the day were just beginning.