
We extend our deepest condolences to the family, friends, and colleagues of Jiří Čížek, distinguished professor emeritus of applied mathematics, who died on December 24, 2024, in Toronto. He was 86.
Čížek was born in Prague, Czechoslovakia (now Czechia) on 24 August, 1938, to Václav Čížek and Jiřina Čížková, both physicians. An avid reader and mathematics student from an early age, by 17 Čížek had mastered algebra and calculus at the level of a university graduate. He began collaborating with lifelong mentor Jaroslav Koutecký in 1955, and published his first two papers with him in 1956, the same year Čížek graduated from high school.
That year he enrolled in the Faculty of Mathematics and Physics at Charles University in Prague, researching kinetic currents and earning his master’s degree there in 1961. He then began doctoral research at the Institute of Physical Chemistry of the Czechoslovak Academy of Sciences (now the J. Heyrovský Institute), graduating in 1965. His research into quantum chemistry and the many-body problem – particularly his proposed use of coupled-cluster methodology for the study of electronic correlation effects in atoms and molecules – laid the groundwork for numerous developments in quantum chemistry over the following decades.
Following the 1968 Warsaw Pact invasion, he moved to Canada with his family and joined the University of Waterloo’s young Applied Mathematics department. He was cross-appointed to the Department of Chemistry in 1973, and throughout the years also served as an affiliate professor at the University of Florida in Gainesville and an adjunct professor at Charles University in Prague. At Waterloo, he supervised or co-supervised six M.Sc. and M.Math. and thirteen Ph.D. theses, and collaborated with numerous post-doctoral researchers, visiting scholars, and colleagues.
A globally recognized researcher in quantum chemistry, Čížek is most well-known for introducing Coupled Cluster Theory to describe electron correlation in atoms and molecules. He authored or co-authored more than 175 papers throughout his career, and received numerous prestigious awards including an Alfred P. Sloan Fellowship and the Alexander von Humboldt Senior Scientist Award (1994).
“Jiří Čížek had an illustrious scientific career and was without doubt one of the giants of intellectual life in the history of Waterloo’s Department of Applied Mathematics,” says Hans De Sterck, chair of the Department of Applied Mathematics. “A number of my colleagues here in the department have known him as a great researcher, teacher, colleague, and friend, and he will be greatly missed.”
Čížek was a member of the International Academy of Quantum Molecular Science and a Fellow of the Royal Society of Canada. He retired from the University of Waterloo in 1996, receiving the title “Distinguished Professor Emeritus,” but continued for years in his work as an adjunct professor at Charles University.
Čížek met his wife Ludamila Zamazalová while in graduate school. The pair married in 1963, and remained inseparable until her death in 2008. “Without her,” Čížek said, “I would finish very badly when I was young.” The couple had two children: Petr, a town and regional planner, and Katerina, an award-winning documentary filmmaker.
Čížek died on Christmas Eve, surrounded by family. His ashes will be interred at the family grave in Prague in a private service.