Dear Sobhan, dear Professor Weidmann, dear family and friends, ladies and gentlemen
It is my great pleasure to welcome you to Sobhan Seyfaddini's inaugural lecture.
Sobhan was born in a small mining town in central Iran in 1982, where he also spent the first eight years of his life – for quite a while the longest stationarity as you soon will see. Next in Tehran, Sobhan attended one of the high schools with world famous mathematics programms, where also Fields Medalist Maryam Mirzakhani has studied shortly before him.
Sobhan then finished high school in Toronto, Canada, and went to Waterloo University, also in Canada, for his undergraduate studies in Mathematics. There his passion for mathematics was ignited (and also a bit of finance was in the blend of the programme).
At Berkely, California, he obtained his PhD on "C0 rigidity in Hofer geometry and Floer theory" under the supervision of Alan Weinstein, a topic which is strongly connected to research done at ETH. Postdoc years brought him to Paris in Claude Viterbo's working group, to MIT in Boston and to the Institute of Advanced Studies in Princeton. In 2017 he received a permanent position at the famous CNRS in Paris with the well sounding job title 'charge de recherche premiere classe'. So a truely cosmopolitean educational trajectory.
Sobhan works in continuous versions of symplectic geometry, a field which grew from the geometry of classical mechanics. The name has been coined by Hermann Weyl, a professor of mathematics at ETH Zurich in the twenties of the last century, as a Greek version of the Latin word 'complex'. Sobhan contributed in the field for instance substantially to the simplicity conjecture. The problem has a long history tracing back to the thirties of the last century, where a group of great mathematicians regularly gathered in the Scottish Cafe of today's Ukrainian city Lviv filling the Scottish Book with all sorts of abstract and applied problems. Stanislav Ulam, inventor of the Monte Carlo Algorithm, suggested a first simplicity problem in the Scottish Book. Later Fields Medalists William Thurston, contributed to this set of deep problems, and even a fearless young postdoc in Vienna around 2000 tried a bit of his luck with a smooth, quantitative version of it. (He went to mathematical finance later and is now standing in front of you.)
Sobhan and his collaborators Dan Cristofaro-Gardiner and Vincent Humiliere finally solved the simplicity conjecture, which states that compactly supported, area preserving homeomorphisms on the open disc are not simple, in an impressive work, which is published in the Annals of Mathematics in 2024. They will be awarded a Frontiers of Science Award for their great contribution to the field in Beijing 2026.
In 2020 he was awarded an ERC starting grant on Homeomorphisms in symplectic topology and dynamics. In 2024 Sobhan has accepted a full professorship in mathematics at D-MATH and he has also expressed his hope to stay first time longer at one place, namely with us in Zurich and at ETH.
We are very much looking forward to Sobhan's inaugural lecture.