On November 20, in awarding the 2014 National Medal of Science to ten distinguished scientists and engineers, President Barack Obama recognized the achievements of three mathematical scientists. Alexandre Chorin (below left), a University Professor at the University of California, Berkeley, was credited with “the development of revolutionary methods for realistic fluid flow simulation, now ubiquitous in the modeling and design of engines, aircraft wings, and heart valves,” as well as in the analysis of natural flows.
Photos courtesy of the National Science & Technology Medals Foundation.
Citing Thomas Kailath (above right), Hitachi America Professor of Engineering Emeritus at Stanford University, “for transformative contributions to the fields of information and systems science,” Obama also recognized his “distinctive and sustained mentoring of young scholars,” as well as his “translation of scientific ideas into entrepreneurial ventures that have had a significant impact on industry.”
David Blackwell (1919–2010), who had been a professor emeritus at UC Berkeley, was honored with a posthumous medal “for fundamental contributions to probability theory, mathematical statistics, information theory, mathematical logic, and Blackwell games, which have had a lasting impact on critical endeavors such as drug testing, computer communications, and manufacturing.”
More on the recipients can be found below and in an upcoming issue of SIAM News.
Origins of a Lifelong Interest in Computation
Mention Alexandre Chorin and many readers would immediately reply “computational fluid mechanics.” Those readers, and in fact anyone in the SIAM community, should be interested in a 2013 interview* with Chorin by his former PhD student and Berkeley colleague James Sethian. It would be hard to top the interview––for which “Is Turbulence Solvable?” would be an apt title––as a survey of Chorin’s life, career, research, and thoughts on the elusive goal of much of his research. The following highlights are offered in the hope that readers, including and perhaps especially students, will visit the Simons Foundation website and access the interview themselves.
Born in Poland less than two years before Hitler invaded, Chorin left with his family for Israel (his first two languages were Polish and Hebrew). Happy in Israel, he resented his family’s move to Geneva (where he picked up his third language: French), and lost his early motivation to be a good student but with his interest in becoming a mathematician (a geometer) intact. After graduating from École Polytechnique Fédérale de Lausanne with a degree in engineering, he returned to Israel, where he was drafted and ended up as a programmer at the Weizmann Institute. Sethian is good at drawing out details about the conditions of computers and computing at the time (the early 1960s), and about inconsistencies in institutional policies, eliciting more than one “It’s complicated” from Chorin.
This was the birth of Chorin’s unswerving lifelong interest in computation, which really took off when he enrolled in a doctoral program at the Courant Institute. He soon settled in at Courant as a student of Peter Lax and had the opportunity to put his programming experience to work on the CDC 6600. As to the evolution of his research, Chorin describes some very early work at Weizmann in which he used the Laplace tidal equation to calculate the height of tides––“a gigantic linear algebra problem”––which affects the motion of satellites, which affects satellite communications. Later, his attention settled on thermal convection, of interest at the time to the U.S. weather bureau, which wanted to predict when thermal inversion would occur and fail to sweep away pollutants near the ground.
Images captured from the Simons Foundation interview.
Of his classes at Courant, Chorin recalls thinking that “For the first time in my life, I’m taking a class in something I actually want to know.” Of New York, Greenwich Village: “It was a ball.” An unexpected but very welcome three-year postdoc at Courant had the effect of delaying the start of his teaching career. As he recalls his earliest teaching experience, a graduate course in numerical analysis at Courant, he covered the entire textbook in three weeks! Throughout his 42 years at Berkeley, he has modulated the pace of his teaching, in courses ranging from beginning undergraduate mathematics through advanced graduate topics. Commenting on the inevitable proliferation of programs in computational science, he worries that students may not learn enough mathematics to be innovative in their work.
Turbulence is the subject of the longest section of the interview. For Chorin, the challenge is nothing less than to compute turbulence from first principles. The Navier–Stokes equations have been known for a century and a half, he points out; what’s needed is a new idea––an idea on the newness scale of chaos. Unwilling to speculate on where that idea will come from, he says only that it is without doubt a mathematics problem.
Recently, he has used some of the tools he learned in fluid mechanics to consider the problem of statistical inference from unreliable models and noisy data, as in weather and economic forecasting––problems that also involve an interaction between probability and differential equations.
We encourage readers to follow Chorin’s years in the Berkeley mathematics department (which he finds remarkable for its absence of rigid boundaries between pure and applied mathematics), and the equally supportive Lawrence Berkeley National Lab, which he considers critical to his happiness at Berkeley.
*Part of the Simons Foundation’s Science Lives collection, in which prominent members of the mathematical sciences community are profiled in essays, taped interviews, or both (in the case of Chorin).
This clip is the first in a series of videos from the interview with Alexandre Chorin.
Jim Crowley, in the midst of preparations for the December meeting of the SIAM Board of Trustees, happened on a draft of this article. Twenty years ago, he pointed out, Alexandre Chorin was a member of the SIAM board. For Crowley, who became SIAM executive director in the fall of 1994, it was his first board meeting. For Chorin, it was the mid-point of a three-year term on the SIAM board––part of a long association with SIAM that has been marked by several honors, including the Norbert Wiener Prize (2000) and in 2009, election to the first class of SIAM Fellows.