We are sad to report that our colleague and friend Leon Green passed away this past summer at the age of 83 years. Leon was born in Passaic, New Jersey. During World War II he trained with the U.S. Coast Guard. After the war, he completed his B.A. degree at Harvard. He had some remarkable teachers there; for example, Henri Cartan, visiting from Paris, taught Leon complex variables. Leon then went to graduate school at Yale, where his thesis adviser was G. A. Hedlund (who in turn was a student of Marston Morse). After a year at Princeton, Leon came to Minnesota, where he became a full professor in 1963. He also had extended mathematical visits in Paris and at Yale. Leon's interests included dynamical systems and differential geometry. Perhaps the most famous of his 28 published papers is "Aufwiedersehensflachen" in the Annals of Mathematics (1963), which is written in English, even though MathSciNet lists it as being in German. The title is a marvelous pun. Blaschke had introduced the concept of Wiedersehensflachen, or "see-you-again surfaces". These are surfaces in which two geodesics leaving any point would meet at a second point of the surface. Leon proved in this paper that the only such surfaces were round spheres, and therefore "bye-bye" to the whole concept!
Leon had seven Ph.D. students, including Nathaniel Grossman who had a prominent career at U.C.L.A. Leon played a key role in the formation of the School of Mathematics as we now know it. Prior to 1963, there were two mathematics departments, one in the College of Engineering and one in Science and Liberal Arts. When the administration agreed to unite the departments, Prof. Neil Amundsen, from Chemical Engineering, was chosen to be the Head, making Leon the Associate Head. Amundsen played the role of a general overseer, while Leon ran the show. He never really enjoyed administration, and was succeeded by Jim Serrin. In cooperation with others, Leon brought distinguished visitors, such as Andre Avez and Marcel Berger, to the School. He continued to serve the department and the differential geometry program here over many years.
He will be greatly missed.