He was one of the leading experts on the theory of dynamical systems.
Born in New York City, he was educated in France.
He was a student at École polytechnique before being one of the first members of the Centre de Mathématiques created there by Laurent Schwartz.
In 1976 he earned his PhD at the Paris-Sud 11 University, under supervision of Harold Rosenberg.
[2] Among his students was Jean-Christophe Yoccoz, 1994 Fields Medalist.