He was born into a
Jewish family in
Győr,
Austria-Hungary and died in
Budapest,
Hungary. Between 1911 and 1919 he was a professor at the
Franz Joseph University in
Kolozsvár, Austria-Hungary. The post-WW1
Treaty of Trianon transferred former Austro-Hungarian territory including Kolozsvár to the
Kingdom of Romania, whereupon Kolozsvár's name changed to
Cluj and the University of Kolozsvár moved to
Szeged, Hungary, becoming the
University of Szeged. and the
Polish Academy of Learning. He was the older brother of the mathematician
Marcel Riesz. Riesz did some of the fundamental work in developing
functional analysis and his work has had a number of important applications in physics. He established the
spectral theory for
bounded symmetric operators in a form very much like that now regarded as standard. and he gave an elementary proof of the mean ergodic theorem. Together with
Alfréd Haar, Riesz founded the
Acta Scientiarum Mathematicarum journal. He had an uncommon method of giving lectures: he entered the lecture hall with an assistant and a
docent. The docent then began reading the proper passages from Riesz's handbook and the assistant wrote the appropriate equations on the blackboard—while Riesz himself stood aside, nodding occasionally. The Swiss-American mathematician
Edgar Lorch spent 1934 in Szeged working under Riesz and wrote a reminiscence about his time there, including his collaboration with Riesz. The corpus of his bibliography was compiled by the mathematician
Pál Medgyessy. ==Publications==