Our colleague Hillel Gershenson died August 6, 2016 after a long illness. Hillel was born March 27, 1935 in New York City. He attended the Bronx High School of Science, and then earned his undergraduate degree at University of Wisconsin, Madison, entering at the age of 16 on the Ford Scholars program. He then spent a year at Harvard as a graduate student in chemistry, during which time he realized that what he really liked was the underlying mathematics, and hence returned to Wisconsin to received his MA degree in math in 1957. He then enrolled in the Ph.D. program at the University of Chicago, writing his thesis on stable homotopy groups of spheres under Professor Eldon Dyer (of Dyer-Lashof operations), and graduating in 1961. Following an instructorship at Princeton University (1961-63) and an assistant professorship at Cornell University (1963-68), during which time he visited the University of Aarhus in Denmark (1966-67), he joined the University of Minnesota in 1968 as Associate Professor of Mathematics. Hillel retired in 2006 to become Associate Professor Emeritus.
Hillel's contributions include an analysis of the relationship between different methods for computing stable homotopy groups of spheres and a beautiful generalization of the Toda bracket, a secondary operation in homotopy groups. Hillel always described what he was doing to curious non-mathematical friends as "most inapplicable mathematics." Once someone asked him at a party what his field of study was, and he said "Algebraic Topology." His friend misheard him as saying "Algebraic Apology" and responded: "Oh, I have been waiting for such a long time for someone to apologize for Algebra!"
Hillel's research focus was algebraic topology, but the teaching of mathematics was a passion. For many years Hillel taught future elementary school teachers as well as worked to improve math education for women and minority students. He served as Director of Graduate Studies as well as Director of Undergraduate Studies several times over his tenure. In a broader university framework, Hillel served two terms on the important Senate Judiciary Committee. He supervised two Ph.D. students: Tod Levitt, co-supervised with David Frank, now at George Mason University, and Melissa Shepard, now at the University of St. Thomas.
Hillel grew up in Bronx, a stone's throw from Yankee Stadium, a team he supported until the Minnesota Twins won his heart. He was a keen birdwatcher and amateur historian. His first degree was in Chemistry and after switching to Mathematics he channeled his chemistry into baking, among his favorites were New York style bagels and Kentucky bourbon cake.
Hillel is survived by his wife of 54 years, Celia Wolk Gershenson, who has been teaching in the Department of Psychology at the University of Minnesota; his sister, Beatrice; his children, Simma and Anne; and his granddaughters, Eleanor and Hazel. His youngest daughter, Rebecca, predeceased him.
A wise, kind-hearted colleague, he will be missed.