Oka Kiyoshi

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Oka in Kyoto 1973

Oka Kiyoshi ( Japanese 岡 潔 ; born April 19, 1901 in Osaka , Japan , † March 1, 1978 in Nara , Japan) was a Japanese mathematician who made fundamental contributions to the theory of the functions of several complex variables.

life and work

Oka studied physics at the Imperial University of Kyoto from 1922 , but switched to mathematics the following year and graduated in 1925. In 1929 he became an assistant professor there and went to Paris at the Sorbonne in the same year , where he worked under the influence of Gaston Maurice Julia (and later the monograph by Heinrich Behnke and Thullen published in 1934) became interested in the theory of several complex variables. When he returned to Japan in 1932, he became an assistant professor at Hiroshima University . In 1938 he studied for himself in Kimitoge in Wakayama Prefecture and in 1940 submitted his doctoral thesis at the University of Kyoto. After a short time as a research assistant at the University of Hokkaidō , he devoted himself to his own research for seven years with the support of a scholarship he received under the influence of Takagi . In 1949 he became a professor at the Nara Women's University , which he remained until 1964. 1969–1978 he was a professor at the Kyōto Sangyō Daigaku .

In several works from the mid-1930s onwards, Oka solved a number of important problems in the analysis of several complex variables (cousin problems, Levi problem). His work was original and difficult to understand at the time, but was taken up by Henri Cartan and his school as part of the sheaf theory.

The Levi problem in particular is about the unambiguous characterization of holomorphic regions of functions of several complex variables. In 1942, Oka showed that a region G is a holomorphic region if and only if each of its boundary points g is pseudoconvex. Pseudoconvex means that for every neighborhood U of g all connected components of are again holomorphic regions. In 1953 he showed that holomorphic areas can also be characterized in this way for general ones.

Oka was highly regarded in Japan for his scientific work and received several awards, including a. 1953 the Asahi Prize , 1960 the Order of Culture .

literature

  • S. Noma (Ed.): Oka Kiyoshi . In: Japan. An Illustrated Encyclopedia. Kodansha, 1993, ISBN 4-06-205938-X , p. 1136.
  • Ingo Lieb : Das Levische Problem , in Bonner Mathematische Schriften, Heft 387, 2007, PDF file (with a short biography and photo)
Collected Treatises
  • Kiyoshi Oka: Sur les fonctions analytiques de plusieurs variables . Iwanami Shoten, Tokyo, Japan 1961, p. 234 (French). (contains bibliographical references; new edition 1983)
  • Reinhold Remmert (Ed.): Kiyoshi Oka Collected Papers . Springer-Verlag, 1984, ISBN 3-540-13240-6 , pp. 223 (English).
Published work

Web links

Individual evidence

  1. ↑ Hironaka (Interview Notices American Mathem.Society October 2005) describes the behavior of Oka to start publishing only 10 years after graduation as "a little crazy". As a result, he was only able to achieve a position at the University of Nara , which was relatively unpredictable in view of its importance .
Japanese name: As is common in Japan, the family name comes before the first name in this article . Thus Oka is the family name, Kiyoshi the first name.
personal data
SURNAME Oka, Kiyoshi
ALTERNATIVE NAMES 広 中 平 祐 (Japanese)
BRIEF DESCRIPTION Japanese mathematician
DATE OF BIRTH April 19, 1901
PLACE OF BIRTH Osaka , Japan
DATE OF DEATH March 1, 1978
Place of death Nara , Japan