was a Japanese

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

who did fundamental work in the theory of

several complex variables The theory of functions of several complex variables is the branch of mathematics dealing with functions defined on the complex coordinate space \mathbb C^n, that is, -tuples of complex numbers. The name of the field dealing with the properties ...

Biography

Oka was born in

Osaka is a Cities designated by government ordinance of Japan, designated city in the Kansai region of Honshu in Japan. It is the capital of and most populous city in Osaka Prefecture, and the List of cities in Japan, third-most populous city in J ...

. He went to

Kyoto Imperial University , or , is a national research university in Kyoto, Japan. Founded in 1897, it is one of the former Imperial Universities and the second oldest university in Japan. The university has ten undergraduate faculties, eighteen graduate schools, and t ...

in 1919, turning to mathematics in 1923 and graduating in 1924. He was in

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

for three years from 1929, returning to

Hiroshima University is a Japanese national research university located in Higashihiroshima and Hiroshima, Japan. Established in 1929, it was chartered as a university in 1949 following the merge of a number of national educational institutions. Its abbreviated f ...

. He published solutions to the first and second

Cousin problems In mathematics, the Cousin problems are two questions in several complex variables, concerning the existence of meromorphic functions that are specified in terms of local data. They were introduced in special cases by Pierre Cousin in 1895. They a ...

, and work on domains of holomorphy, in the period 1936–1940. He received his

Doctor of Science A Doctor of Science (; most commonly abbreviated DSc or ScD) is a science doctorate awarded in a number of countries throughout the world. Africa Algeria and Morocco In Algeria, Morocco, Libya and Tunisia, all universities accredited by the s ...

degree from Kyoto Imperial University in 1940. These were later taken up by

Henri Cartan Henri Paul Cartan (; 8 July 1904 – 13 August 2008) was a French mathematician who made substantial contributions to algebraic topology. He was the son of the mathematician Élie Cartan, nephew of mathematician Anna Cartan, oldest brother of c ...

and his school, playing a basic role in the development of

sheaf Sheaf may refer to: * Sheaf (agriculture), a bundle of harvested cereal stems * Sheaf (mathematics) In mathematics, a sheaf (: sheaves) is a tool for systematically tracking data (such as sets, abelian groups, rings) attached to the open s ...

theory. The

Oka–Weil theorem In mathematics, especially the theory of several complex variables, the Oka–Weil theorem is a result about the uniform convergence of holomorphic functions on Stein spaces due to Kiyoshi Oka and André Weil. Statement The Oka–Weil theorem sta ...

is due to a work of

André Weil André Weil (; ; 6 May 1906 – 6 August 1998) was a French mathematician, known for his foundational work in number theory and algebraic geometry. He was one of the most influential mathematicians of the twentieth century. His influence is du ...

in 1935 and Oka's work in 1937. Oka continued to work in the field, and proved

Oka's coherence theorem In mathematics, the Oka coherence theorem, proved by , states that the sheaf \mathcal_ of holomorphic functions on \mathbb^n (and subsequently the sheaf \mathcal_ of holomorphic functions on a complex manifold X) is coherent.In paper it was ca ...

in 1950.

Oka's lemma In mathematics, Oka's lemma, proved by Kiyoshi Oka, states that in a domain of holomorphy In mathematics, in the theory of functions of several complex variables, a domain of holomorphy is a domain which is maximal in the sense that there exists ...

is also named after him. He was a professor at

Nara Women's University is a national women's university located in Nara, Nara Prefecture, Japan. It is one of two national women's universities in the country, the other being Ochanomizu University.For more about the legal status of "national universities" in Japan, ...

from 1949 to retirement at 1964. He received many honours in Japan.

Honors

* 1951 Japan Academy Prize * 1954

Asahi Prize The , established in 1929, is an award presented by the Japanese newspaper ''Asahi Shimbun'' and Asahi Shimbun Foundation to honor individuals and groups that have made outstanding accomplishments in the fields of arts and academics and have greatl ...

* 1960

Order of Culture The is a Japanese Order (decoration), order, established on February 11, 1937. The order has one class only, and may be awarded to men and women for contributions to Japanese Art, Japan's art, Japanese Literature, literature, science, technolog ...

* 1973 Order of the Sacred Treasure, 1st class

Bibliography

*KIYOSHI OKA COLLECTED PAPERS ** - Includes bibliographical references. ** **

Selected papers (Sur les fonctions analytiques de plusieurs variables)

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Biography

Honors

Bibliography

Selected papers (Sur les fonctions analytiques de plusieurs variables)

References

External links