**Theodor Estermann ** was a German mathematician who worked in the field of analytic number theory.

- Immanuel Estermann (1900-1973) became an outstanding physicist.
- Leo Estermann was a Zionist, a passionate believer in the formation of a state of Israel, and strongly opposed to the integration of Jews into the societies in which they lived.
- Theodor's first schooling was in Hamburg where, from 1908, he attended the Talmud-Torah School, the oldest Jewish school in Hamburg founded in 1805.
- Theodor felt happier in the state primary than he had in the Talmud-Torah School.
- Immanuel attended a school where he was able to undertake practical science experiments in laboratories but the school that Theodor attended did not have such facilities for science.
- It seems that this difference between the schools may have led to Immanuel becoming fascinated by chemistry (he later moved to physics) while Theodor developed a passion for mathematics.
- Estermann entered the University of Göttingen, the leading German university for mathematics, and there he attended courses by David Hilbert and Edmund Landau.
- Now although Rademacher was by this time turning towards number theory and Estermann's interests were in that area after attending Edmund Landau's lectures in Göttingen, Rademacher still did not feel confident enough to suggest a number theory topic to Estermann; instead, he suggested a problem in measure theory.
- Estermann was awarded his doctorate in 1925 for his thesis Über Carathéodorys und Minkowskis Verallgemeinerungen des Laengenbegriffs Ⓣ(On Carathéodory's and Minkowski's generalizations of quantity terms) and, in the same year, he published a paper with the same title as his thesis.
- Estermann had visited her for a holiday in 1924 while he was a research student at Hamburg.
- This was a highly productive period for Estermann with papers: Über den Vektorenbereich eines konvexen Körpers Ⓣ(On the vector field of a convex body) (submitted September 1927); On the Representations of a Number as the Sum of Three Products (submitted April 1928); and On the Divisor-Problem in a Class of Residues (submitted July 1928).
- Back in Hamburg before taking up the position in London, Estermann sent off his paper On the Representations of a Number as the Sum of Two Products (a 2-part paper, the first part submitted June 1929, second part November 1929).
- Theodor Estermann was an invited speaker at the Colloquium on the 'Theory of Numbers' held at the University of Bristol in June 1935.
- Estermann published Introduction to Modern Prime Number Theory in 1952.
- Estermann published the undergraduate text Complex Numbers and Functions in 1962.
- It must be difficult for readers who have never met Estermann to appreciate the author's personality.
- Klaus Roth recalls from his research student days that his supervisor, Dr Estermann, could still demonstrate faultless handstands with the same facility with which he made his many erudite (but apt) quotations from Shakespeare and Gothe.
- In 1965, four years before he retired, University College London promoted Estermann to professor.

Born 5 February 1902, Neubrandenburg, Germany. Died 29 November 1991, London, England.

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Origin Germany

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive