Walter Littman was born on September 17, 1929 in Vienna, Austria. He and his family escaped the Nazis in an extraordinary tale of survival, mettle and luck. His life — and the lives of thousands of other Jews — tragically changed when the Nazis annexed Austria in March 1938. His father, Leon,a fabric merchant, was arrested in the Kristallnacht pogrom that destroyed synagogues and Jewish-owned businesses the following November. According to the family, Leon escaped almost-certain execution because he coughed while being interrogated by the Nazis. Believing Leon was days away from death, S.S. Capt. Adolf Eichmann, one of the architects of the Holocaust,reportedly told him he “wasn’t worth the bullet”. He was then released,but they had just days to flee Austria or face deportation to a concentration camp. The Littmans escaped to Sweden and spent 1940-1941 in Göteborg while awaiting U.S. visas. In 1941, they took the Trans-Siberian railroad across Russia to Vladivostok, and then boarded a ship to Japan, followed by a ship to the United States. The family ultimately settled in the Lower East Side of New York City, opening a drapery business.
Walter was accepted to the prestigious Stuyvesant High School, known for its programs in science, technology and mathematics. He went on to receive his B.A, from New York University in 1952. He completed his Ph.D. at the Courant Institute in NYU four years later,1956, under the direction of Louis Nirenberg, who also advised our colleague Wei-Ming Ni. Walter's Ph.D. thesis was titled "On the Existence of Gravity Waves near Critical Speed". He then spent three years as an instructor/lecturer at the University of California, Berkeley, followed by a year as an assistant professor at the University of Wisconsin. He joined the University of Minnesota as assistant professor of mathematics in 1960. (In those days, there were two Mathematics Departments, and Walter was in the one in the Institute of Technology, which later became the College of Science and Engineering. (The departments were merged in 1965.)
In 1960, right before coming to Minnesota, Walter married Florence. They moved into a house in Prospect Park, where they lived for many years, alongside many other Math Department families. Walter and Florence had three children: Philip, Miriam, Benjamin. He was quickly promoted to associate professor in 1963 and full professor in 1966. He returned to Sweden in 1974-75 as a visiting professor at the Mittag-Leffler Institute and Chalmers Technological University, and was at the Hebrew University in Jerusalem during 1981-82. Among his many services to the Department and University, he served for many years as the Master of Ceremonies at departmental meetings and dinners, where he made good use of his endless supply of jokes and quips. In addition to his beloved equations, Littman enjoyed classical music, particularly the work of Austrian composer Franz Schubert. After suffering a stroke, Walter retired with the rank of Emeritus Professor in 2010. Ten years after his retirement, at age 90, Walter sadly succumbed to the COVID-19 pandemic on April 17, 2020.
Walter was a prolific and highly cited researcher in analysis and partialdifferential equations, with well over 60 papers published over the years, many coauthored with current and former colleagues, including Avner Friedman, Nestor Riviere, Gene Fabes, Luis Caffarelli, Hans Weinberger, Bob Gulliver, Larry Markus, and Satya Kichenassamy. His paper with Weinberger and the renowned Italian mathematician Guido Stampacchia on regularboundary points for uniformly elliptic partial differential equations is considered a classic in the field. In later years he wrote a series of influential papers on control theory for partial differential equations,and was a pioneer in introducing direct methods for exact controllability, rather than by duality via observability estimates. He was highly involved in the School of Mathematics' many initiatives in industrial mathematics, and edited an IMA volume on the topic with Avner Friedman. Walter supervised 8 Ph.D. students at Minnesota, almost all finishing in the 1990's.
A special issue of the journal "Evolution Equations and Control Theory", dated Dec. 2013, was dedicated to Walter's retirement. Quoting from the preface to this volume: "Walter has a remarkable ability to network which arises from a wonderful combination of characteristics; a very friendly, gentle, generous nature, a great interest in people, a great interest in exchanging ideas with people, and an extremely robust memory for people and their work. Everyone who has visited Walter’s office at the University of Minnesota has a similar story to tell: One is greeted at the door by Walter’s broad, friendly smile. There is only just enough space for Walter and one guest because the office is filled, floor to ceiling with stacks of papers and books. During the conversation, Walter reaches out to these papers and pulls out precisely the ones relevant to the conversation. No need for an electronic version of mathematical reviews or computer archives!"
Walter was a mainstay of the School of Mathematics and, in particular, its world renowned analysis research group. He had a major impact on both the mathematical and social lives of the Department, and his jovial and collegial presence will be sorely missed.