Person: Helly, Eduard
Helly worked on functional analysis and proved the HahnBanach theorem in 1912 fifteen years before Hahn published essentially the same proof and 20 years before Banach gave his new setting.
Mathematical Profile (Excerpt):
 Wirtinger arranged a scholarship for Helly so that he could continue his studies at Göttingen and he went there after graduating from Vienna.
 At Göttingen Helly studied under Hilbert, Klein, Minkowski and Runge in 19078.
 One might have expected that the end of World War 1 in 1918 would have led to Helly's release but by this time the Russian armies were fighting each other and escape was impossible.
 Even after leaving Russia it was a long route back to Vienna for Helly who travelled through Japan, the Far East, Egypt and the Middle East before reaching home in 1920.
 partly because Helly was Jewish and also because Hahn thought a younger person should be preferred.
 Helly was forced to earn a living working in a bank, then as an actuary when the bank collapsed in 1929.
 Helly was dismissed from his post because he was a Jew.
 He is remembered for Helly's theorem, published in 1923, which states that if there are given nnn convex subsets of a ddddimensional Euclidean space with n≥d+1n ≥ d+1n≥d+1 and if each collection of d+1d + 1d+1 of the subsets has a point in common then there is a common point of the nnn subsets.
 First there is Helly's selection principle which says that given a sequence of functions of bounded variation which are of uniform bounded variation and uniformly bounded at a point, then there exists a subsequence which converges to a function of bounded variation.
 There are other results in the paper which should have given Helly a much higher profile in the world of mathematics than he has achieved.
 In most careers there are some disappointments and failures, but Helly's career derailed early, and life never gave him a chance to get back on the right track.
Born 1 June 1884, Vienna, Austria. Died 28 November 1943, Chicago, Illinois, USA.
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Origin Austria
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References
Adapted from other CC BYSA 4.0 Sources:
 O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive