Please answer the following question: Facts: - doctoral students: hans falckenberg friedrich neuhaus - known for: riesz -- fischer theorem - fields: mathematics - death date: 14 november 1954 - workplaces: university of cologne - doctoral advisor: franz mertens leopold gegenbauer - birth date: 12 july 1875 - name: ernst s. fischer - nationality: austria - death place: cologne - birth place: vienna - alma mater: university of vienna Based on these bullet points, write a short biography describing the life of ernst sigismund fischer .
A:
ernst sigismund fischer -lrb- 12 july 1875 -- 14 november 1954 -rrb- was a mathematician born in vienna , austria .he worked alongside both mertens and minkowski at the universities of vienna and zurich , respectively .he later became professor at the university of erlangen , where he worked with emmy noether .his main area of research was mathematical analysis , specifically orthonormal sequences of functions which laid groundwork for the emergence of the concept of a hilbert space .the riesz -- fischer theorem in lebesgue integration is named in his honour .