Walter Littman

In Memoriam

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 partial
differential 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 regular
boundary 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.