Leopold Fejér

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Leopold Fejér
Tomb on the Kerepesi temető

Leopold Fejér (Hungarian Fejér Lipót ; born February 9, 1880 in Pécs as Leopold Weiss ; † October 15, 1959 in Budapest ) was a Hungarian mathematician who dealt with analysis .

Leopold Weiss took on the name Fejér around 1900 in the course of the Magyarization of the Hungarian Jews during his stay in Berlin . Fejér studied mathematics and physics in Budapest from 1897 (as a student of Julius König , József Kürschák , Manó Beke , Loránd Eötvös ) and Berlin (1899/1900), where he was a student of Hermann Amandus Schwarz , Lazarus Fuchs and Georg Frobenius . In Berlin he also made friends with Erhard Schmidt , Issai Schur , Edmund Landau and Constantin Carathéodory . He received his doctorate in 1902 from Loránd Eötvös University (with a dissertation supervised by Schwarz). In 1905 he became a professor in Kolozsvár (which was partly due to the recognition of Henri Poincaré , which he expressed on the occasion of a visit to Budapest in order to receive the Bolyai Prize) despite opposition that existed at the time against Jewish faculty members. In the winter of 1902/03 he was in Göttingen, where he attended lectures by David Hilbert and Hermann Minkowski , and in the summer of 1903 in Paris, where he heard Émile Picard and Jacques Hadamard . From 1911 until his death he held a chair for mathematics at the Loránd Eötvös University in Budapest. The events of the First World War, during which he fell seriously ill, and the Horthy regime afterwards weighed on him, as did the events of the Second World War in Budapest towards the end of his life, which forced him to resign in 1944 because of his Jewish origins. His mental abilities quickly deteriorated and he died of a stroke in a hospital in 1959.

His research focus was harmonic analysis and the field of Fourier series . Fejér's theorem is named after him , which is of great importance in the theory of the Fourier series and which at the time improved its reputation in the eyes of mathematicians despite their sometimes pathological behavior (among other things, they could be used to construct continuous, nowhere differentiable functions). The sentence arose from his dissertation. He also dealt with power series, potential theory, approximation theory, conformal mapping.

Fejér received the Kossuth Prize in 1948 . In 1912 he was Vice President of the International Congress of Mathematicians in Cambridge and in 1911 he became a member of the Hungarian Academy of Sciences. He was a member of the Göttingen Academy of Sciences (1917), the Bavarian Academy of Sciences (1954) and the Polish Academy of Sciences (1957). He was an honorary doctor from Brown University and Lorand Eötvös University. He was co-editor of the mathematical journal and the Rendiconti del Circolo matematico di Palermo .

Fejer was a good pianist.

Web links

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Individual evidence

  1. Leopold Fejér in the Mathematics Genealogy Project (English)Template: MathGenealogyProject / Maintenance / id used
  2. Sur les fonctions bornées et intégrables. In: Comptes rendus hebdomadaires des séances de l'Académie des Sciences. Volume 131, 1900, pp. 984-987 .
  3. Holger Krahnke: The members of the Academy of Sciences in Göttingen 1751-2001 (= Treatises of the Academy of Sciences in Göttingen, Philological-Historical Class. Volume 3, Vol. 246 = Treatises of the Academy of Sciences in Göttingen, Mathematical-Physical Class. Episode 3, vol. 50). Vandenhoeck & Ruprecht, Göttingen 2001, ISBN 3-525-82516-1 , p. 79.