Person: Fischer, Ernst Sigismund
Ernst Fischer is best known for the Riesz-Fischer theorem in the theory of Lebesgue integration.
Mathematical Profile (Excerpt):
- Ernst was educated in Vienna, and he studied at the University of Vienna under Mertens from 1894.
- From 1911 until 1920, Fischer was professor at the University of Erlangen, appointed to fill the chair left vacant in the previous year when Paul Gordan retired.
- When Fischer arrived in Erlangen it was natural for Noether to work with him.
- She refers in her papers at this time again and again to conversations with Fischer.
- Fischer is best known for one of the highpoints of the theory of Lebesgue integration, called the Riesz-Fischer Theorem.
- From 1920 Fischer worked at the University of Cologne, remaining there until he retired in 1938.
- Let us note again the major result, the Riesz-Fischer Theorem, for which he is best known as Weyl noted in the above quote.
- In 1907 Ernst Fischer studied orthonormal sequences of functions and gave necessary and sufficient conditions for a sequence of constants to be the Fourier coefficients of a square integrable function.
- The theorem, now called the Riesz-Fischer theorem, is one of the great achievements of the Lebesgue theory of integration.
- Fischer went on to study Hadamard determinants, publishing his results in 1908 in the Archiv der Mathematik und Physik, and Sylvester determinants, publishing a paper in Crelle's Journal in the following year.
Born 12 July 1875, Vienna, Austria. Died 14 November 1954, Cologne, Germany.
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Adapted from other CC BY-SA 4.0 Sources:
- O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive