Ernst Sigismund Fischer (12 July 1875 – 14 November 1954) was a mathematician born in

Vienna, Austria en, Viennese , iso_code = AT-9 , registration_plate = W , postal_code_type = Postal code , postal_code = , timezone = CET , utc_offset = +1 , timezone_DST ...

. He worked alongside both

Mertens __NOTOC__ Mertens () is a surname of Flemish Origin, meaning "son of Merten" (Martin). It is the fifth most common name in Belgium with 18,518 people in 2008. Geographical distribution As of 2014, 43.4% of all known bearers of the surname ''Merte ...

and Minkowski at the Universities of

Vienna en, Viennese , iso_code = AT-9 , registration_plate = W , postal_code_type = Postal code , postal_code = , timezone = CET , utc_offset = +1 , timezone_DST ...

and Zurich, respectively. He later became professor at the

University of Erlangen A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, th ...

, where he worked with

Emmy Noether Amalie Emmy NoetherEmmy is the '' Rufname'', the second of two official given names, intended for daily use. Cf. for example the résumé submitted by Noether to Erlangen University in 1907 (Erlangen University archive, ''Promotionsakt Emmy Noeth ...

. His main area of research was

mathematical analysis Analysis is the branch of mathematics dealing with continuous functions, limits, and related theories, such as differentiation, integration, measure, infinite sequences, series, and analytic functions. These theories are usually studied ...

, specifically orthonormal sequences of functions which laid groundwork for the emergence of the concept of a

Hilbert space In mathematics, Hilbert spaces (named after David Hilbert) allow generalizing the methods of linear algebra and calculus from (finite-dimensional) Euclidean vector spaces to spaces that may be infinite-dimensional. Hilbert spaces arise natural ...

. The Riesz–Fischer theorem in

Lebesgue integration In mathematics, the integral of a non-negative function of a single variable can be regarded, in the simplest case, as the area between the graph of that function and the -axis. The Lebesgue integral, named after French mathematician Henri Le ...

is named in his honour. He is the grandson of composer Karl Graedener.Ernst Sigismund Fischer http://www-history.mcs.st-andrews.ac.uk/Biographies/Fischer.html.

References

External links

* * Austrian mathematicians Austrian expatriates in Switzerland Austrian expatriates in Germany Scientists from Vienna 1875 births 1954 deaths Austro-Hungarian mathematicians {{europe-mathematician-stub