Professor Toshiyuki KOBAYASHI Receives the Fujihara Award
Professor Toshiyuki KOBAYASHI of the Graduate School of Mathematical Sciences, The University of Tokyo, who also serves as a Senior Fellow at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), has been awarded the Fujihara Award. The award ceremony was held on June 17, 2026.
The Fujihara Award, established by the Fujihara Foundation of Science, is one of Japan’s most prestigious honors, presented to individuals who have made distinguished contributions to the advancement of science and technology in the natural sciences. Each year, two awards are given across five fields: mathematics and physics, chemistry, engineering, biological and agricultural sciences, and medicine. Among those affiliated with the University of Tokyo, previous recipients include Distinguished University Professors Masatoshi KOSHIBA (1997), Yoshinori OHSUMI (2005), and Yoshinori TOKURA (2011).
Professor KOBAYASHI’s award is particularly notable in the field of mathematics, as it marks the first time since Professor Kunihiko KODAIRA, who received the award as Professor Emeritus in 1975, that a member of the Department of Mathematics, Faculty of Science, has been honored, and the first time that a current faculty member of the Graduate School of Mathematical Sciences has received the award since its establishment in 1992.
Kobayashi is being recognized for his contributions to “Mathematical Analysis of Infinite-Dimensional Symmetries.”
For more than 35 years, he has led mathematical research on the international stage. His work on infinite-dimensional symmetries has formulated and identified previously unrecognized fundamental problems, integrating algebra, geometry, and analysis at a profound level.
Kobayashi’s work on the problem of restrictions and branching of infinite-dimensional representations—long considered difficult to understand systematically—discovered discretely decomposable restrictions, thereby making him the first to theorize their structure.
Furthermore, he was the first to establish a comprehensive general theory of the action of discontinuous groups in geometry without a metric structure. He also introduced an original theory of “visible actions” on complex manifolds, establishing a unified framework for generating multiplicity-free representations in both finite- and infinite-dimensional settings.
Kobayashi also carried out pioneering work in introducing conformal geometry into minimal representations, leading to a new field known as “global analysis with minimal representations as a motif.” His work on the construction and classification theory of symmetry-breaking operators has played a central role in the development of new research fields over the past 15 years.
His contributions have been highly acclaimed internationally, and in 2025, a three-volume Festschrift of approximately 2,000 pages was published by an international academic publisher, underscoring the significance of his work.
Professor KOBAYASHI has received numerous honors, including the MSJ Spring Prize, the Inoue Prize for Science, the Humboldt Research Award, the Medal with Purple Ribbon, Fellowship of the American Mathematical Society, and an honorary doctorate from the University of Reims (France). He has also made significant contributions to strengthening the University’s role as a global research hub through interdisciplinary research at Kavli IPMU and the establishment of the French-Japanese Laboratory of Mathematics and its Interactions.
This award recognizes Professor KOBAYASHI’s long-standing and outstanding contributions to original and pioneering research. The University of Tokyo extends its sincere congratulations and wishes him continued success in his future endeavors.
The Fujihara Award, established by the Fujihara Foundation of Science, is one of Japan’s most prestigious honors, presented to individuals who have made distinguished contributions to the advancement of science and technology in the natural sciences. Each year, two awards are given across five fields: mathematics and physics, chemistry, engineering, biological and agricultural sciences, and medicine. Among those affiliated with the University of Tokyo, previous recipients include Distinguished University Professors Masatoshi KOSHIBA (1997), Yoshinori OHSUMI (2005), and Yoshinori TOKURA (2011).
Professor KOBAYASHI’s award is particularly notable in the field of mathematics, as it marks the first time since Professor Kunihiko KODAIRA, who received the award as Professor Emeritus in 1975, that a member of the Department of Mathematics, Faculty of Science, has been honored, and the first time that a current faculty member of the Graduate School of Mathematical Sciences has received the award since its establishment in 1992.
Kobayashi is being recognized for his contributions to “Mathematical Analysis of Infinite-Dimensional Symmetries.”
For more than 35 years, he has led mathematical research on the international stage. His work on infinite-dimensional symmetries has formulated and identified previously unrecognized fundamental problems, integrating algebra, geometry, and analysis at a profound level.
Kobayashi’s work on the problem of restrictions and branching of infinite-dimensional representations—long considered difficult to understand systematically—discovered discretely decomposable restrictions, thereby making him the first to theorize their structure.
Furthermore, he was the first to establish a comprehensive general theory of the action of discontinuous groups in geometry without a metric structure. He also introduced an original theory of “visible actions” on complex manifolds, establishing a unified framework for generating multiplicity-free representations in both finite- and infinite-dimensional settings.
Kobayashi also carried out pioneering work in introducing conformal geometry into minimal representations, leading to a new field known as “global analysis with minimal representations as a motif.” His work on the construction and classification theory of symmetry-breaking operators has played a central role in the development of new research fields over the past 15 years.
His contributions have been highly acclaimed internationally, and in 2025, a three-volume Festschrift of approximately 2,000 pages was published by an international academic publisher, underscoring the significance of his work.
Professor KOBAYASHI has received numerous honors, including the MSJ Spring Prize, the Inoue Prize for Science, the Humboldt Research Award, the Medal with Purple Ribbon, Fellowship of the American Mathematical Society, and an honorary doctorate from the University of Reims (France). He has also made significant contributions to strengthening the University’s role as a global research hub through interdisciplinary research at Kavli IPMU and the establishment of the French-Japanese Laboratory of Mathematics and its Interactions.
This award recognizes Professor KOBAYASHI’s long-standing and outstanding contributions to original and pioneering research. The University of Tokyo extends its sincere congratulations and wishes him continued success in his future endeavors.
Related links
- Past Recipients of the Fujihara Award (The Fujihara Foundation of Science)
- Professor Toshiyuki Kobayashi’s website
- Comprehensive overview of Professor KOBAYASHI's work: Goldman et al., "The Mathematical Work of Toshiyuki Kobayashi" Progress in Mathematics, Birkhäuser-Springer, pp. 1-102, 2025.
