Helly

Eduard Helly

Born: 1 June 1884 in Vienna, Austria
Died: 28 Nov 1943 in Chicago, Illinois, USA

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Eduard Helly studied at Göttingen under Hilbert, Klein, Minkowski and Runge in 1907-8. He worked on functional analysis and proved the Hahn-Banach theorem in 1912 fifteen years before Hahn published essentially the same proof and 20 years before Banach gave his new setting.

While serving during World War I he was shot and captured in 1917, remaining a prisoner in Russia until 1920. Helly was appointed to Vienna in 1921 to an unpaid post, earning a living working in a bank then as an actuary when the bank collapsed. He was dismissed from his insurance company in 1938 because he was a Jew. He emigrated to the USA.

He is remembered for Helly's theorem which states that if there are given n convex subsets of a d-dimensional euclidean space with n gte d+1 and if each collection of d+1 of the subsets has a point in common then there is a common point of the n subsets.

References:

  1. Dictionary of Scientific Biography
  2. P L Butzer, R J Nessel and E L Stark, Eduard Helly (1884-1943) : In memoriam, Resultate der Mathematik 7 (1984).
  3. H Hochstadt, Eduard Helly, Father of the Hahn-Banach Theorem, Mathematical Intelligencer 2 (1980), 123-125.
  4. V M Tikhomorov, Eduard Helly, Istoriko- matematicheskie issledovaniya 32-33 (1990), 137-145. 
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