Jean Leray (1906-1999)

Jean Leray was one of the outstanding mathematicians of the 20th century. While it is well-known that Leray discovered spectral sequences and sheaf theory (which was eventually developed by J P Serre), and made substantial contributions to various other fields in both pure and applied mathematics (fluid dynamics, hyperbolic equations, fixed points theorems, to name a few of the most important), it is less known that Leray also created Lagrangian Anlysis, which is a rigorous geometric approach to the asymptotic theory of partial differential equations depending on a small parameter (for instance Planck's constant h). He thus gave solid mathematical foundations to Maslov's theory. Part of my own work has been devoted to developing further Leray's ideas on these topics.

Jean Leray was my mentor for the "Habilitation à diriger des Recherches" I passed at the University of Paris 6 in 1992; at that time he was 86 years old.  He was one more counterexample to Hardy 's infamous claim in Apology of a Mathematician following which "...mathematics is a young man's game...."

I organized in 1999, together with J. Vaillant (Paris), the first Conference in the Honour of Jean Leray. This conference took place in Karlskrona, at the Blekinge Institute of Technology. The Proceedings are published by Kluwer/Springer. Leray wanted to attend this conference, and was scheduled to deliver the Inaugural Lecture. He died a few months before the conference, undergoing an operation following a fall. The inaugural lecture was given by his former student and long time friend, Madame le Professor Yvonne Choquet-Bruhat, who was the first woman mathematician to become a member of the French Académie des Sciences.

Here is a (non-exhaustive) list of participants:

B. Booss-Bavnbek (Roskilde), L. Boutet de Monvel (Paris), Y. Choquet-Bruhat (Paris), S. Cappell (Courant Institute) P. Dazord (Lyon), K. Furutani (Tokyo), B. Gaveau (Paris), Y. Hamada (Kyoto), C. Houzel (Paris), S. Illman (Helsinki), R. Lee (Yale), P. Libermann (Paris), C.-M. Marle (Paris), W. Schempp (Siegen), J. Snyaticki, G. Tuynman (Lille), J. Vaillant (Paris), C. Wagschal (Toulouse),...

http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Leray.html

http://www.diplomatie.gouv.fr/label_france/ENGLISH/SCIENCES/mathematiciens/mathematiciens.html

http://www-users.mat.uni.torun.pl/~tmna/htmls/mem1.html