Tribute to Philippe Tondeur

Picture above: Philippe Tondeur at the ICM 2006 in Spain.

Philippe Tondeur passed away on October 15, after a rich and fulfilling life shared with his wife, Claire-Lise—a life devoted to mathematics and to serving the mathematical community, whether in his own field of research, his department, or his adopted country, the United States of America. In one of our last conversations, he wrote to me: “My experiences in the world of mathematics have been among the greatest joys of my life.”

I have lost a very dear friend with whom I had the pleasure of exchanging mathematical ideas in conversations that extended far beyond differential geometry, a field in which we both shared a particular interest. I also benefited greatly from his expertise in his favorite subject, foliation theory. These exchanges took place at institutions around the world and came all the more naturally because many of his collaborators were also close friends of mine.

His remarkable powers of persuasion proved especially effective during his tenure as Director of the NSF’s Division of Mathematical Sciences from 1999 to 2002, when he succeeded in nearly doubling its budget. I had the opportunity to appreciate his vision for the future of our discipline during our many discussions at the conference “Mathematical Challenges of the 21st Century”, held in Los Angeles in August 2000 as part of the celebrations marking World Mathematical Year 2000. He believed that mathematics should give data science its rightful place in the years to come—an idea that was far from obvious at the time.

IHES owes an immense debt of gratitude to Philippe and his wife for the exceptional gift they made in 2024, which enabled the creation of a Permanent Professor’s Chair at the Institute. Marilyn and Jim Simons joined them in this initiative by matching their contribution. Philippe and Claire-Lise wished to associate my name with this chair, a very special honor that I accepted because of our longstanding friendship, built over the years on mutual trust.

This gift had been preceded by another, intended to support the Institute’s efforts to involve artists in some of its projects—a cause that was dear to both of us.

Jean-Pierre Bourguignon
Nicolaas Kuiper Honorary Professor and former Director of IHES

Photo Credit: © MFO