# Obituary: Ivar Stakgold

Mathematician Ivar Stakgold, professor emeritus at the University of Delaware (UD), passed away on May 29, 2018, at the age of 92. He specialized in boundary value problems, was a well-known bridge player, and served SIAM in multiple roles — most notably as president from 1989 to 1990.

Ivar was born in 1925 near Oslo, Norway, and spent much of his early childhood in Brussels, Belgium. To escape the onset of World War II in 1940, his family embarked upon a torturous journey through France, Spain, and Portugal to reach the Dominican Republic. They immigrated to the U.S. in 1941 and settled in New York.

Ivar earned a B.S. (in 1945) and an M.S. (in 1946) in engineering from Cornell University. In 1949, he received a Ph.D. in applied mathematics from Harvard University under the direction of Léon Brillouin. Ivar taught at Harvard until 1956, when he became head of the mathematics and logistic branches at the Office of Naval Research in Washington, D.C.

In addition to his prowess as a mathematician, Ivar was a world-class bridge player. He played on teams that won national championships in the late 1950s and early 1960s, and even represented the U.S. in the 1959 Bermuda Bowl, a biennial bridge world championship. His team finished second to the famous Italian “Blue Team.”

*Boundary Value Problems of Mathematical Physics*, which were published in 1967 and 1968. These volumes appeared in SIAM’s

*Classics in Applied Mathematics*series in 2000, demonstrating the enduring value of his contribution.

While at Northwestern, Ivar formed the Committee on Applied Mathematics, which offered engineering graduate students the opportunity to earn a Ph.D. in applied mathematics. In 1969, he became chair of the Department of Engineering Sciences — the forerunner of Northwestern’s current Department of Engineering Sciences and Applied Mathematics.

In 1964, Ivar married Alice Cox. They welcomed their daughter Alissa in 1965 and remained married until Alice’s death in 1994. Alice shared Ivar’s interest in high-level bridge competition, and they played as partners on a team that won a national mixed team championship in 1969.

In the late 1960s, applied mathematicians expressed a growing interest in nonlinear problems that exhibited bifurcating solutions. Ivar combined the essential contributions of various researchers in the field to write a seminal review paper for *SIAM Review* entitled “Branching of Solutions of Nonlinear Equations,” which was published in 1971. This highly-cited paper contributed significantly to the widespread investigation of bifurcation phenomena in the subsequent decades.

In 1975, Ivar left Northwestern to become a professor of mechanical engineering and professor and chair of UD’s Department of Mathematical Sciences. He was a highly-skilled administrator. In anticipation of expanding mathematics at UD, Ivar began his tenure by negotiating for added space to accommodate the burgeoning graduate program and an active visitor program. As chair, his impressive presence, quick mind, acerbic wit, and keen analytical powers helped him motivate and maintain peace among the members of his department.

Ivar continued as chair of the department until 1991. During his 16-year stewardship, the department’s reputation grew among the worldwide mathematical community; this elevation of prestige was certainly due in part to the new faculty members that he recruited.

While serving as chair, Ivar maintained his own active research program and wrote another graduate-level textbook in 1979 called *Green’s Functions and Boundary Value Problems*. Later editions of this book, which are still widely used, appeared in 1998 and 2011, the latter co-authored with Michael Holst of the University of California, San Diego.

Ivar also contributed to SIAM in many ways. He was a member of the Board of Trustees from 1975 to 1984 (the maximum allowable term), served as chair of the Board, and was president from 1989 to1990. Ed Block, founder and longtime managing director of SIAM, described Ivar as particularly skilled in conducting Board meetings during contentious discussion. When SIAM initiated its Fellows Program in 2009, Ivar was among the inaugural class of members.

Additionally, he was chair of the Conference Board of the Mathematical Sciences, served as director of the Washington Office of the American Mathematical Society, and held various visiting professorships at institutions around the world, including in Italy, Spain, Switzerland, New Zealand, and England. Following his retirement in 1995, Ivar was appointed professor emeritus at UD.

In 2008, Ivar moved to California and took a position as a research scientist at UC San Diego. He is survived by his daughter Alissa and his fiancée Lainie Lesser-Mark, who was a close companion during the last decade of his life.

We will miss Ivar’s personality and continuing contributions to applied mathematics.

Pam Cook is Unidel Professor of Mathematics, associate dean of engineering, and professor of chemical engineering at the University of Delaware (UD). She succeeded Ivar Stakgold as chair of the Department of Mathematical Sciences at UD, and later as president of SIAM. | |

W. Edward Olmstead is professor emeritus of applied mathematics at Northwestern University, where Ivar was one of his Ph.D. mentors. When Ivar left Northwestern in 1975, Olmstead assumed his role in developing the graduate program in applied mathematics. |