Leo Kadanoff, leading figure in theoretical physics, 1937-2015

Theoretical physicist Leo Kadanoff, who transformed theory and practice across scientific disciplines, died of respiratory failure on Oct. 26 in Chicago. He was 78.

“Leo was a prodigious scientist,” said his longtime UChicago colleague Sidney Nagel, the Stein-Freiler Distinguished Service Professor in Physics. “His work on statistical mechanics is one of the great achievements of 20th-century theoretical physics. It laid the conceptual and mathematical foundations for some of the most insightful and effective tools on which our modern understanding of nature is based.”

Kadanoff’s work has applications throughout physics, ranging from condensed matter (liquids and solids) to elementary particles, Nagel said, with the reach of his work extending to mathematics and other sciences.

Kadanoff received the 1999 National Medal of Science, the nation’s highest science honor, from President Bill Clinton in a White House ceremony. Kadanoff was cited “for leadership in fundamental theoretical research in statistical, solid-state and nonlinear physics, which has led to numerous and important applications in engineering, urban planning, computer science, hydrodynamics, biology, applied mathematics and geophysics.”

In 2013, UChicago received a $3.5 million gift from anonymous donors to support the Leo Kadanoff Center for Theoretical Physics. The center brings together physicists who ordinarily work in a specialty such as particle physics, relativity theory or condensed matter theory and encourages them to work on problems of interest in all of those areas.

In the 1960s, Kadanoff made innovative and original contributions to the understanding of phase changes, such as the change of water from liquid to ice. In later years, working in collaboration with students, junior scientists and colleagues, he helped construct a new field of knowledge called soft condensed matter physics, which deals with such phenomena as the flow of fluids and the behavior of granular materials.

Kadanoff was especially interested in how complexity arises from simple phenomena, such as avalanches forming from the forces that are transmitted between grains of sand. A skilled teacher of colleagues, graduate students and undergraduates, one of his contributions was to use and to show others how to use computer models and simplified conceptual models for better understanding the world.

Curator and cultivator

Kadanoff had been active at the James Franck Institute until a few weeks before his death. One of his particularly important contributions there in his final years was to lead the long-running Computations in Science seminars.

“This was easily the most influential seminar connected with the physics department,” said longtime UChicago colleague Thomas Witten, the Homer J. Livingston Professor Emeritus in Physics.

“Its strategy was to scout actively for the most promising topics that would attract many disciplines, from math and physics to chemistry and geology. Its success was due to Leo’s persistent search for the most exciting topics and speakers. He evolved gracefully from his series of landmark discoveries in statistical physics to his last role of curator and cultivator.”

Nagel also commented on Kadanoff’s ability to attract the attention of scientists from multiple disciplines.

“Here at the University, he was the center of so much activity that it is difficult to imagine the campus without him,” Nagel said. “He had an extraordinary breadth of interests with a keen eye and appreciation for novel and imaginative science of all kinds.”

Kadanoff championed that work to his colleagues and was central to the culture of collaboration in the Physical Sciences Division. “When he saw an opportunity, he brought many of us together to attack a problem from different perspectives,” Nagel noted.

At Kadanoff’s funeral on Oct. 28, his daughter Marcia Kadanoff remarked that her father underwent a sea change during his 50s regarding his role in life. He started viewing his main work as developing people, rather than making prize-winning discoveries.

“The Leo I knew was all about developing people,” Witten said.

Born Jan. 14, 1937 in New York City, Kadanoff received his bachelor’s, master’s and doctoral degrees from Harvard University. After completing his doctorate in 1960, Kadanoff conducted postdoctoral research at the Bohr Institute for Theoretical Studies in Copenhagen. He joined the faculty of the University of Illinois at Urbana-Champaign in 1962, where he remained until joining the Brown University faculty in 1969.

He and his wife, the former Ruth Viterbo, had been together since 1975.

Distinguished professorship

Kadanoff became a professor of physics at UChicago in 1978 and was named the John D. and Catherine T. MacArthur Distinguished Service Professor of Physics and Mathematics in 1982. He directed UChicago’s Materials Research Center from 1981 to 1984 and from 1994 to 1997.

He also had served as a visiting professor at Cambridge University in 1965, and as the Lorentz Professor at the University of Leiden in The Netherlands in 2003. He retired as professor emeritus in 2003 but remained professionally active, serving as president of the American Physical Society in 2007.

Kadanoff had received many honors during his career. These included the Wolf Foundation Prize in Physics, the Grande Medaille d’Or of the Académie des Sciences de l’Institut de France, the American Physical Society’s Onsager and Buckley prizes, the Franklin Institute’s Elliott Cresson Medal, the Boltzmann Medal of the International Union of Pure and Applied Physics, and the Lorentz Medal of the Royal Dutch Academy of Sciences. He also was a member of the National Academy of Sciences and a fellow of the American Academy of Arts and Sciences, the American Association for the Advancement of Science, of the American Physical Society, and of the Alfred P. Sloan Foundation.

Kadanoff was further recognized for his undergraduate teaching. At UChicago he designed a new undergraduate course, “Chaos, Computers and Physics.” Nominated by his students, he received the University’s prestigious Quantrell Award for Excellence in Undergraduate Teaching in 1990.

Survivors include his wife, Ruth; daughters, Marcia Kadanoff, Felice Kadanoff, Betsy Kadanoff and stepdaughter Michal Ditzian; and grandchildren, Alexandra Mironov, Benjamin Clemens, Sophia Clemens and Reuben Clemens. Funeral services were held. In lieu of flowers, memorials may be made in his memory to the Kadanoff Center for Theoretical Physics, c/o Kathleen Conroy, University of Chicago James Franck Institute, 929 E. 57th St., Room 145, Chicago, IL 60637.