**Kosaku Yosida** was a Japanese mathematician who worked in the field of functional analysis.

- Yosida graduated with his first degree in 1931, having taken mathematics as his main subject.
- In 1933 Yosida was appointed as an Assistant in the Department of Mathematics at Osaka Imperial University.
- The Osaka Imperial University is based on educational institutions dating back to the 18th century but only became a university in 1931, two years before Yosida was appointed there.
- Moving to Osaka Imperial University led to Yosida changing the direction of his research.
- Yosida became interested in functional analysis through discussions with these two mathematicians.
- Yosida's main task at Professor of Mathematics was to promote and expand the newly established Department of Mathematics and this he did very successfully, through much hard work, along with his colleagues.
- It is now called the Hille-Yosida theory ....
- The influence of this theory was far-reaching: Yosida and many others applied it to numerous areas in analysis such as diffusion equations, Markov processes, hyperbolic equations, and potential theory.
- Yosida published Topological Analysis in Japanese in 1951.
- This book was expanded and modernised by Yosida when he published his classic work Functional Analysis (1965).
- In 1953 Yosida returned to Osaka University when he was appointed Professor in the Department of Mathematics there.
- Back in Japan, Yosida moved to Tokyo when he was appointed as Professor in the Department of Mathematics at the University of Tokyo.
- Yosida remained a professor at the University of Tokyo until he retired in March 1969 when he reached the age of sixty.
- After retiring from Tokyo University, Yosida became Director of the Research Institute for Mathematical Analysis, Kyoto University, holding this position from 1972 to 1976.
- Yosida attended the Congress and gave a short presentation entitled On the differentiability of a semi-group of operators.
- Yosida was an Honorary Member of the Organising Committee of the Congress but sadly died in June 1990, two months before the Congress took place.
- Yosida published a number of important books.
- In addition to these books, Yosida wrote, in collaboration with colleagues, a number of mathematical textbooks in Japanese.
- Yosida played a major role in the Mathematical Society of Japan.
- The Japan Academy awarded Yosida their Emperor's Prize in 1967.
- The book is divided into 10 sections following the main topics on which Yosida worked.
- An extensive bibliography of all Yosida's papers, both English and Japanese, is included.
- This edition will prove invaluable to anyone wanting a comprehensive view of Yosida's work.

Born 7 February 1909, Hiroshima, Japan. Died 20 June 1990, Tokyo, Japan.

View full biography at MacTutor

Origin Japan

**Oâ€™Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive