Person: Helly, Eduard
Helly 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.
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 1907-8.
- 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 ddd-dimensional 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.
View full biography at MacTutor
Tags relevant for this person:
Origin Austria
Thank you to the contributors under CC BY-SA 4.0! 
- Github:
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- non-Github:
- @J-J-O'Connor
- @E-F-Robertson
References
Adapted from other CC BY-SA 4.0 Sources:
- O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive
