Professor Emeritus Irving Segal, 79, a pioneer in the fields of functional analysis and harmonic analysis, died unexpectedly while walking near his home in Lexington, MA, on August 30. The cause of death was atherosclerotic cardiovascular disease.
An MIT faculty member for 38 years, Professor Segal was one of the Department of Mathematics' most dedicated teachers, contributing significantly to the review and upgrading of its curriculum. He was advisor to a number of outstanding graduate students, among them MIT professors Isadore Singer and Bertram Kostant (now emeritus) and Princeton professor Edward Nelson.
"His encouragement was strong when I was writing a thesis," Professor Nelson recalled in an introduction to the 1983 book Studies in Applied Mathematics, which is dedicated to Professor Segal, "and equally important was his total lack of encouragement when I found a result unrelated to anything beyond itself. This sense of the global nature of mathematical research is one of the most valuable things that he imparts to his students."
Born in the Bronx on Sept. 13, 1918, Professor Segal was raised in Trenton, NJ, and received the BA from Princeton in 1937 and the PhD from Yale in 1940, both in mathematics. He was an instructor at Harvard University in 1941 and a research associate at Princeton from 1941-43 before entering the US Army as an enlisted man. After military service during which he performed ballistics research at the Aberdeen (MD) Proving Grounds, Professor Segal did research work at the Institute for Advanced Study from 1945-48 before moving to the University of Chicago. He was an assistant professor from 1948-53, an associate professor from 1953-57 and a full professor from 1957-60. He came to MIT in 1960 as a professor of mathematics and assumed emeritus status in 1989.
Early in his career, Professor Segal was concerned with applications of algebraic methods to fundamental physics, in particular to the foundations of quantum field theory. In 1947 he introduced a system of postulates for general quantum mechanics which reworked a number of key concepts in quantum theory and spawned a great deal of active research.
He was able to generalize major portions of the seminal work of Norbert Wiener. His theory of non-commutative integration provided an extraordinary generalization of the Plancherel theorem for the Fourier transform to general (cq) locally compact groups.
More recently, Professor Segal pursued applications of his "chronometric theory" to various studies in astrophysics, leading to a parameter-free theory of the red-shift and an alternative model of the universe.
Professor Segal, a member of the American Astronomical, Mathematical, and Physical Societies, was elected to the American Academy of Arts and Sciences, the Royal Danish Academy of Sciences, and the National Academy of Sciences. A three-time John Simon Guggenheim Fellow (1947, 1951 and 1967) and recipient of the Alexander von Humboldt Award in 1981, he was a founder and managing editor of the Journal of Functional Analysis and authored three books and more than 200 papers.
Professor Segal had visiting professorships at universities around the world, including Columbia, La Sorbonne, Lund University, University of Pisa, Aarhus University, College de France, Institute of Mathematics and Theoretical Physics, Copenhagen, and the University of Moscow. He loved both jazz and classical music.
Professor Segal is survived by his wife, Dr. Martha (Fox) Segal of Lexington; their eight-year-old daughter, Miriam, of Lexington; three children from an earlier marriage, William of Bethesda, MD, Andrew of Espinola, NM, and Karen of New York City; and four grandchildren. His first wife, Osa MacLane of Chicago, mother of William, Andrew and Karen, also survives.
A memorial gathering was held at MIT yesterday. Burial was private.
A version of this article appeared in MIT Tech Talk on September 16, 1998.