The School of Mathematics expresses its profound sadness upon the passing of Hans Weinberger on Friday, September 15, 2017, in Durham, NC. Hans was a mainstay of the School during its modern era, and formed an essential component of its pre-eminence in analysis. He was renowned for his contributions to the analysis of partial differential equations, especially eigenvalue problems. He turned his attention to mathematical biology later in his career, and was active in research throughout his life. Indeed, even in retirement one could always see Hans hard at work (at least when not napping!) in his office on the fifth floor of Vincent Hall. Hans was also famous for seeming to doze off in seminar talks, only to engage the speaker at the end with his penetrating insight and questions.
Hans received his Ph.D. in 1950 from Carnegie Tech (now Carnegie-Mellon University). He joined the University of Minnesota in 1960 as full professor, and, after many years of dedicated service, retired to take on the role of professor emeritus in 1998. During that time he served as Department Head in 1967-69. Over the years, he supervised 9 Ph.D. students, including such notable mathematicians as Bert Hubbard, Roger Lui, John Osborne, and Jianzhong Su. According to MathSciNet, Hans published 114 papers, the earliest in the Proceedings of the National Academy of Sciences in 1952, and continued to publish well into his retirement, the last appearing in 2015. Prominent coauthors include David Gilbarg, Joe Keller, Mark Lewis, Larry Payne, George Pólya, Murray Protter, and Guido Stampacchia, as well as colleagues such as Don Aronson, Roger Fosdick, Leonid Hurwicz, Walter Littman, David Sattinger, and Jim Serrin. (In particular, he and Serrin wrote a Russian language paper whose authors on MathSciNet are listed as Serrin, Džeĭms and Vaĭńberger, Gans F.) Hans was honored by being elected a member of the American Academy of Arts and Sciences in 1986, and was in the inaugural class of Fellows of the American Mathematical Society in 2012. Hans was also the author of three influential books. His undergraduate text A First Course in Partial Differential Equations, published in 1965, was used in classes thourhgout the world, and introduced generations of undergraduates to this essential area of pure and applied mathematics. He also coauthored, with Murray Protter, a research monograph on Maximum Principles, an area in which he made profound contributions, as well as writing a book on Variational Methods for Eigenvalue Approximation that was based on his series of lectures that was the centerpiece of a Conference Board of Mathematical Sciences (CBMS) Regional Conference at Vanderbilt University in1972.
Hans was born in Vienna, Austria on September 27, 1928. The story of how he came to study and work in America is of interest, and illustrates how a tragic period of history altered lives and in many cases benefited education in the United States. Hans' mother and father both studied medicine in Vienna, with a specialty in dentistry and oral surgery, and they worked together in his grandfather's practice. As the Nazis in Germany began to threaten Austria, as well as Jews in general, it seemed certain that Hitler would soon take over Austria. An uncle who was also a medical doctor had emigrated to the U.S. and wrote that the time had come to start applying for visas. They applied for several, and the ones for the U.S. came in first. So, in the Fall of 1938 they set sail for America and eventually settled in Altoona, Pennsylvania.
Hans demonstrated an early aptitude for the sciences. He was a finalist in the Westinghouse Talent Search at the age of 17, receiving this recognition for designing a self-inflating life vest for the US Navy. Since he lived in Pennsylvania, it was logical that Hans attended Carnegie Tech, enrolling at a very young age. He stayed on to write a thesis under the direction of Richard Duffin, and counted John Nash and Raoul Bott, a fellow advisee, as classmates. By the age of 21, he had earned his Doctorate in Mathematics, and then joined the faculty of the University of Maryland in College Park where he spent ten years at the Institute for Fluid Dynamics and Applied Mathematics. As a young professor living in Washington D.C. Hans met his wife, Laura while attending a social event. He remained at Maryland for 10 years, and was then invited, by the Department Head Stefan Warschawski, to come to Minnesota. Hans became an integral part of the golden age for partial differential equations here, initiated by Art Milgram and Paul Rosenbloom, and his colleagues included Jim Serrin, Don Aronson, Walter Littman, Eugene Calabi, among others. He just missed having Hidehiko Yamabe as a colleague.
In 1979, in response to the National Science Foundation’s request for proposals to establish a Mathematical Sciences Research Institute, Hans, George Sell, and Willard Miller, the then Department Head, submitted a proposal to establish the Institute for Mathematics and its Applications (IMA) at the University of Minnesota. They boldly envisioned a mathematics institute that would look outward from the core of mathematics toward applications. Its goal was to bring mathematicians together with scientists to focus on problems from other disciplines and from industry, and to create new research that would have an impact on the science as well as enriching mathematics itself. With the successful funding of the IMA by NSF, Hans went on to serve as its first director, from 1982 to 1987. Under his leadership, the IMA quickly became known for its cutting-edge scientific programs, its unique atmosphere that encourages collaboration, and as a training ground for postdoctoral researchers. During his tenure, Hans was a very engaged in the scientific life at the IMA, attending lectures and collaborating with visitors and postdocs. A recent director of the IMA, Fadil Santosa, has said "I am the caretaker of the house that Hans built".
Hans is survived by his wife, Laura, his daughters, Catherine and Sylvia, and son, Ralph, and their families, including 8 grandchildren and a great-grandson. Mathematics and collaboration with colleagues remained a lifelong passion for Hans, who made a daily bus trip to his office as a Professor Emeritus for 18 years following his "retirement" up until he and Laura moved to North Carolina in 2016 to be closer to their family. And he continued to develop differential equations on the backs of envelopes until he left us. In spite of his impressive accomplishments, Hans was the most modest and accessible person one could ever meet, and was exceptionally generous with his time and his ideas. He will be sorely missed.