Person: Riesz, Frigyes
Riesz was a founder of functional analysis and his work has many important applications in physics.
Mathematical Profile (Excerpt):
 Frigyes (or Frederic in German) Riesz studied at Budapest.
 Riesz was a founder of functional analysis and his work has many important applications in physics.
 In 1907 and 1909 Riesz produced representation theorems for functional on quadratic Lebesgue integrable functions and, in the second paper, in terms of a Stieltjes integral.
 A satisfactory theory of series of orthonormal functions only became possible after the invention of the Lebesgue integral and this theory was largely the work of Riesz.
 Riesz's work of 1910 marks the start of operator theory.
 Riesz was appointed to a chair in Kolozsvár in Hungary in 1911.
 In Szeged in 1922 Riesz set up the János Bolyai Mathematical Institute in a joint venture with Haar.
 Riesz became editor of the newly founded journal of the Institute Acta Scientiarum Mathematicarum which quickly became a major source of mathematics.
 Riesz was to publish many papers in this journal, the first in 1922 being on Egorov's theorem on linear functionals.
 In 1945 Riesz was appointed to the chair of mathematics in the University of Budapest.
 Many of Riesz's fundamental findings in functional analysis were incorporated with those of Banach.
 His theorem, now called the RieszFischer theorem, which he proved in 1907, is fundamental in the Fourier analysis of Hilbert space.
 Riesz made many contributions to other areas including ergodic theory where he gave an elementary proof of the mean ergodic theorem in 1938.
 The more leisurely mastership of F Riesz's style, whether he writes in his native Hungarian, or in French or German, conveys such pleasure and is to the older mathematician a nostalgic remainder of what we are in danger to lose.
 With it, and with all his other work, will live the memory of Frederic Riesz as a great and fertile mathematician for long in the history of our art.
 Riesz received many honours for his work.
Born 22 January 1880, Györ, AustriaHungary (now Hungary). Died 28 February 1956, Budapest, Hungary.
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Tags relevant for this person:
Origin Hungary, Physics, Topology
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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