Short Bio

I was born in Paris, France, in 1958. In French politics, this is the year of the birth of La Cinquième République (the Fifth Republic, Charles de Gaulle becomes President). In mathematics, this is the year when Harry Kesten earned his Cornell Ph.D. with a thesis titled Symmetric Random Walks on Groups under the supervison of Mark Kac. 

I was raised in Montbard, a town with a population of about 7,000 in Côte-d'Or, in the north part of Bourgogne (Burgundy). Montbard is the birth place of Georges-Louis Leclerc, Comte de Buffon, naturalist, mathematician and encyclopédiste. In mathematics, Buffon is known for his pioneering use of Statistics and for the Buffon's needle problem which provides a method to approximate the number pi using a needle. Buffon is perhaps most famous today for his contributions to the development of the Jardin des Plantes in Paris. Created in the 17th century by Jean Héroard and Guy de la Brosse at the behest of King Louis XIII, the Jardin des Plantes, was devoted at first to medicinal species. In the 18th century, it became a centre for research and a Muséum, spearheaded by Buffon.

I studied in Paris, at Université Pierre et Marie Curie (Paris VI, now part of Sorbonne University) where I earned a Licence (1979), a Maîtrise (1980), a Ph.D. (Doctorat de troisième cycle, 1983) and a Doctorat d’État (1989), all in Mathematics. During that period, I met my friend Thierry Coulhon who had many good advices on how to pursue graduate studies in mathematics. As a graduate student and researcher in Paris, I was a member of the Laboratoire d'Analyse Complexe et Géometrie who was led successively by Pierre Dolbeault and Michel Hervé. My advisor was Nicholas Th. Varopoulos. 

In 1981, I became Professeur Agrégé (high school teacher, civil servant) and, as I was working on my Ph.D., I taught at lycée Jules Uhry (Creil, Oise) and lycée Cassini (Clermont, Oise). I then taught at the lycée Charles de Gaulle in London for two years (1983-85) before returning to Université Pierre et Marie Curie (Professeur Agrégé, en détachement, PRAG).

In 1988, I became Chargé de Recherche at CNRS (Centre National de la Recherche Scientifique). During the next few years, I spent about half of my time in Paris and the other half visiting Daniel Stroock at MIT (Massachussetts Institute of Technology). During that time, I started my long term collaboration with Persi Diaconis who was Professor at Harvard at the time, and I met and worked with Waldek Hebisch. My wife, Cathy, and I met in Boston. Cathy died in February 2021.

In 1992, I became Directeur de Recherche (CNRS) and moved to Toulouse where I was a memmber of the Laboratoire de Statistique et Probabilités now part of the Institut de Mathématiques de Toulouse at Université Paul Sabatier, Toulouse III. I spent five wonderful years in Toulouse, in constant interaction with Michel Ledoux and Dominique Bakry. During that time, I started long term collaborations with Christophe Pittet, Alexander Grigor'yan, and  Alexander Bendikov. Cathy and I bought our first house in Pins-Justaret and our son, Samuel, was born in Toulouse in 1996. We moved to Ithaca, NY, USA, in 1998 and our daughter, Claire, was born in Ithaca that year. 

I have been Professor of Mathematics at Cornell since 1998. I served as Chair of the Department of Mathematics, July 1st 2009-December 31 2015.