Hermann Kober

Hermann Kober (* 1888 in Beuthen ; † October 4, 1973 in Birmingham ) was a German-British mathematician.

Life

Kober came from a Jewish family in Silesia, his father was a tailor. He attended school in Breslau and studied mathematics in Berlin, Göttingen (with Edmund Landau ) and Breslau, where he received his doctorate in 1911 with Adolf Kneser with a dissertation on calculus of variations (conjugated kinetic foci). Then he was a math teacher at the Johannes-Gymnasium in Breslau. In the First World War he was a soldier and was wounded. In the 1920s he studied law alongside his teaching profession and received his doctorate in law in 1930, but never practiced the profession. From the 1930s he began to publish mathematically again, before that he had only published his dissertation. After the National Socialists came to power, he was dismissed from school, but continued to teach at a Jewish school. In 1936 he married the mathematician Kate Silberberg, who took up his teaching position while he was in Cambridge doing research. Godfrey Harold Hardy got him a scholarship to Birmingham University and in 1939 he moved to England. In 1940 he received a Master of Science there and in 1943 a D.Sc. His main occupation was from 1943 to 1962 as a mathematics teacher at a grammar school in Birmingham.

Kober published on special functions, real analysis, conformal mappings (about which he wrote a lexicon on behalf of the British Admiralty in the 1940s), approximation theory, fractional integration and differentiation (Erdelyi-Kober operators with Arthur Erdélyi ) and functional analysis, among others Kober's theorem, which specifies necessary and sufficient conditions for the sum M + N of two sets M, N closed in X in the Banach space X to be closed with in X. It is then closed just when there is a constant there, so for all , applies . ${\displaystyle M\cap N={0}}$ ${\displaystyle A>0}$ ${\displaystyle x\in M}$ ${\displaystyle y\in N}$ ${\displaystyle ||x||\leq A\cdot ||x+y||}$

Fonts

• Dictionary of conformal representations, 5 volumes, 1944-1948, Reprint Dover 1952

literature

• WHJ Fuchs: Hermann Kober, Bull. London Math. Soc., Volume 7, 1975, pp. 185-190.

Web links

• John J. O'Connor, Edmund F. Robertson :  Hermann Kober. In: MacTutor History of Mathematics archive .

Individual evidence

1. ↑ Kober, On fractional integrals and derivatives, The Quarterly Journal of Mathematics, Volume 11, 1940, pp. 193-211
2. ↑ Kober, A theorem on Banach spaces, Composition Mathematica, Volume 7, 1940, pp. 135-140, numdam