Tribute to Sergio Doplicher (1940 – 2025)

Sergio Doplicher, a distinguished mathematician and theoretical physicist, passed away on September 9, 2025. Born in 1940 in Trieste, he devoted most of his career to Sapienza University of Rome, where he served as a professor in the Department of Mathematics from 1976 to 2011, and became professor emeritus in 2012. Prior to that, he taught at the Université de Marseille (1967–1971) and was a research associate at Princeton University.

Sergio Doplicher was a plenary speaker at the International Conference in Kyoto on Mathematical Problems of Theoretical Physics (1975) and an invited speaker at the International Congress of Mathematicians in Kyoto (1990). Among his many honors are the Humboldt Research Award (2004), the Premio Nazionale del Presidente della Repubblica awarded by the Accademia Nazionale dei Lincei (2011), and the title of Fellow of the American Mathematical Society (2012).

In 2000, an international conference held in Siena already paid tribute to his lifetime achievements, a testament to the deep recognition he received from the scientific community.

His work opened essential avenues in fields as varied as the theory of abstract duality for compact groups, the structure of operator algebras, and the algebraic description of quantum fields.

As one of his former students, Claudia Pinzari, recalls:
“Sergio was deeply committed to certain works, beyond those listed among his major works, notably the article published in Annals of Mathematics with John Roberts, entitled “Endomorphisms of C*-algebras, cross products and Duality for Compact Groups.”

Beyond his scientific contributions, Sergio Doplicher was highly regarded for his generosity and intellectual curiosity. A longtime friend, Arthur Jaffe, confirms: “Sergio was a unique, generous, and kind person, interested in many aspects of life. His memory is a treasure for me.“

Sergio Doplicher leaves the legacy of a researcher of exceptional rigor and a thinker of great intellectual elegance, whose work continues to inspire physicists and mathematicians in their quest to understand the foundations of the quantum world.

His connection with IHES is described in his own words in a text published on the American Mathematical Society website in October 2019:
“About a month after receiving my Laurea in Rome, I went to IHES for a semester, drawn by an exceptional gathering of long-term visitors, including Arthur Wightman, Harry Lehmann, and Hans Borchers, the Olympus of what was then called ‘axiomatic quantum field theory.’ But its operator-algebra variant, pioneered by Haag, Kastler, and Araki, had already sparked my interest. So, when Arthur one day told me at tea time, ‘Dick Kadison will come here in spring 1964,’ it sounded like the announcement that the second peak of the Parnassus was coming to us. To my great surprise and delight, the expected visitor was not a distant immortal, but an extremely friendly person, always ready to share his immense knowledge with young beginners like me. We continued to meet frequently in the following years, first at IHES, then in Bandol, at Daniel Kastler’s residence.”

IHES is pleased to know that Sergio Doplicher appreciated the welcoming atmosphere during his stays. His enthusiasm for research, intellectual curiosity, and generosity in sharing knowledge have left a lasting mark on the Institute.