Robert W. Zwanzig, Distinguished University Professor and Professor Emeritus in the Institute for Physical Science and Technology, died quietly in his sleep on May 15. Bob Zwanzig had a very distinguished career as a teacher and researcher in the field of statistical physics. He joined the faculty of the University of Maryland in 1968 and retired in 1988, after which he joined the Chemical Physics Division of the National Institutes of Health. He was elected to the National Academy of Sciences in 1972, was awarded the Debye Prize from the American Chemical Society in 1976 and received the Langmuir Award from the American Chemical Society in 1984.
A brilliant theoretical physicist and chemist, Bob was well known for his ability to describe a wide variety of physical phenomena using very sophisticated model systems of his own invention, and he possessed the mathematical skills to obtain results from them with striking clarity. His deep insights into equilibrium and non-equilibrium statistical mechanics have influenced these fields profoundly. Bob's 1954 paper on thermodynamic perturbation theory, published in the Journal of Chemical Physics when he was in his mid-20s, provides one of the foundations of modern computational thermodynamics.
Bob may best be known for his “projection operator method,” which allows one to obtain equations for time-dependent distributions and correlation functions in a very simple and direct way, showing that a technical breakthrough can lead to a deeper conceptual understanding of the behavior of many-particle systems. This method continues to be widely used by workers of all generations in his field.
Bob Zwanzig was a great teacher of graduate students and mentor to younger scientists. With insights and skills that were greatly admired, in many instances he helped his colleagues to successfully find their way in their own research efforts. He will be greatly missed.