Kiyoshi Oka

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

Life and work

Oka studied from 1922 at the Imperial University of Kyoto physics, but changed the following year to mathematics and graduated in 1925. 1929 he became assistant professor and went in the same year in Paris at the Sorbonne, where he was under the influence of Gaston Maurice Julia (and later the monograph published in 1934 by Heinrich Behnke and Thullen ) for the theory of several complex variables began to be interested. On his return to Japan in 1932 he became an assistant professor at the University of Hiroshima. In 1938 he studied for in Kimitoge in Wakayama Prefecture in 1940 and handed his doctoral thesis at the University of Kyoto one. After a short time as a research assistant at the University of Hokkaido, he went back for seven years with the support of a scholarship, which he received on the influence of Takagi own research. In 1949 he became professor at the Nara Women's University, a position he held until 1964. 1969-1978 he was a professor at Kyoto Sangyo Daigaku.

In several works from the mid-1930s Oka triggered a series of important problems in analysis of several complex variables ( Cousin problems, Levi problem). His works were original and difficult to understand at that time, but were picked up by Henri Cartan and his school in the context of sheaf theory.

Especially when Levi problem concerns the unambiguous characterization of Holomorphiegebieten of functions of several complex variables. Oka showed in 1942 for that region G if is a domain of holomorphy if each of its boundary points, g is pseudoconvex. Pseudoconvex means that for every neighborhood U of g all connected components of domains of holomorphy are again. In 1953 he showed that it is possible domains of holomorphy for general be characterized.

Oka was highly regarded for his scientific work in Japan and has received several awards, including 1953 Asahi Prize.