Eduard Helly

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Eduard Helly (born June 1, 1884 in Vienna , † November 28, 1943 in Chicago , Illinois ) was an Austrian mathematician .

Life

Eduard Helly is one of the founders of functional analysis. He studied mathematics at the University of Vienna with Wilhelm Wirtinger and Franz Carl Joseph Mertens . After his dissertation in 1907 on Fredholm integral operators, Wirtinger arranged for him to go on a scholarship at the University of Göttingen , where he heard from David Hilbert , Felix Christian Klein and Hermann Minkowski . He succeeded u. a. to prove a special case of the Hahn-Banach theorem , 15 years before Hahn himself (published in 1912, the related work by Hahn was published in 1927, that by Banach in 1929). Banach was familiar with Helly's work from 1912 and also quoted it, which is not entirely clear with Hahn. Both use an inequality introduced by Helly for proof. His first independent publication in 1911 went about a sentence from the theory of linear functional operations . He then earned his living as a private teacher, high school teacher and by writing solution books for math textbooks.

During the First World War he was a lieutenant in the infantry. He was seriously wounded in a lung shot in 1915, which also affected his heart, which contributed to his later heart disease, from which he finally died in 1943. In 1915 he was taken prisoner by Russia. He also wrote fundamental contributions to functional analysis in the prisoner of war camp near Nikolsk-Ussuriysk , Siberia . After the end of the war he did not reach Vienna again until 1920 after crossing Japan, Asia and Egypt (he could not take the direct route via Russia due to the turmoil of the civil war). In 1921 he married the mathematician Elise Bloch and completed his habilitation in the same year at the University of Vienna, but never received a professorship there. That was probably partly because he was Jewish (the University of Vienna was known for its anti-Semitism) and partly because Hahn preferred a younger lecturer.

During these years he frequented the Viennese Café Central and discussed a. a. with Hermann Broch , Philipp Frank and Hahn.

He worked in a bank until 1929 and, when it went bankrupt, in an insurance company until 1938. During this time he occasionally held seminars in his apartment and gave lectures at the university, but due to his workload did not get to do extensive mathematical research. As a Jew, he threatened to lose his license to teach with Hitler's invasion of Austria . In the same year, Helly emigrated to the USA with his wife. With Einstein's support , he got an insignificant position at Paterson Junior College in New Jersey and in 1941 moved to Monmouth Junior College in the same state. During the war years, he and his wife worked on the mediation of Isaac Albert Barnett (1894–1974) for the US Army Signal Corps in Chicago, a communications engineering facility of the US Army.

Just five weeks after he finally received his first chair at the Illinois Institute of Technology in 1943 , he died of a repeated heart attack.

He is particularly known for Helly's theorem from convex geometry. The set of Helly-Bray and the selection set of Helly are named after him. The first movement deals with the weak convergence and the vague convergence of measures and their relation to the convergence of distribution functions , the second with the existence of vague convergent subsequences of sequences of measures. Helly's selection theorem can also be formulated as follows: uniformly bounded function sequences of uniformly bounded variation have subsequences which converge at every point to a function with bounded variation. Harry Hochstadt attributes the neglect of these contributions by Helly to the unusual life path of Helly, who after an unintentional interruption due to the First World War worked in other professions for a long time before he was able to return to academic work.

In his 1912 work, Helly anticipated not only Hahn-Banach's theorem , but also Banach-Steinhaus's theorem .

literature

Web links

Individual evidence

  1. ^ Harry Hochstadt: Eduard Helly, father of the Hahn-Banach theorem, The Mathematical Intelligencer, Volume 2, 1980, No. 3, pp. 123–125
  2. ↑ Günter M. Ziegler : Where Mathematics Arises , in: Die Zeit , Wochenzeitung, Hamburg, No. 16, April 15, 2010, p. 40
  3. ^ Harry Hochstadt: Eduard Helly, father of the Hahn-Banach theorem, The Mathematical Intelligencer, Volume 2, 1980, No. 3, p. 124
  4. ^ Harry Hochstadt: Eduard Helly, father of the Hahn-Banach theorem, The Mathematical Intelligencer, Volume 2, 1980, No. 3, pp. 123–125
  5. ↑ Helly, About linear functional operators, session reports Akad. Wiss. Vienna, Volume 121, 1912, pp. 265-297
personal data
SURNAME Helly, Eduard
BRIEF DESCRIPTION Austrian mathematician
DATE OF BIRTH June 1, 1884
PLACE OF BIRTH Vienna
DATE OF DEATH November 28, 1943
Place of death Chicago , Illinois