Hans Hamburger

Hans Ludwig Hamburger (* August 5, 1889 in Berlin, † August 14, 1956 in Cologne ) was a German mathematician. He was professor of mathematics at the universities of Berlin, Cologne and Ankara.

Training and Study

His parents' house can be described as classy. His father Karl Hamburg was a lawyer, he worked as a lawyer and notary in Berlin. His mother 's maiden name was Margaret Hamburg Levy. Hamburger attended the French Gymnasium in Berlin. 1907-1914 studied Hans Hamburger in Berlin, Lausanne and Göttingen and at Alfred Pringsheim in Munich, where he was in 1914 his doctorate with a thesis "On the integration of linear homogeneous differential equations ".

After serving from 1915 to 1918 as a soldier in the First World War, he habilitated with the thesis " Extensions of Stieltjes'schen moment problem ", which appeared as a verbatim report of the Bavarian Academy of Sciences, at the University of Berlin. In Berlin, he worked first as a lecturer and from 1922 as associate professor.

The Cologne Years and emigration

1924 followed a reputation Hamburg to Cologne as a full professor at the II Mathematical Institute and director of the Mathematical Institute (next to Ernst Sigismund Fischer). In 1927 he married Malla Jessen. The marriage was, however, later divorced. In his time in Cologne occupied him especially problems of differential geometry, such as the Caratheodorysche presumption to which he published several times, but no definitive solution to the problem.

1935 deprived him of the Nazis, the Venia Legendi, which meant the end of his work at the Mathematical Institute in Cologne. Together with his mother he moved then to Berlin. In 1939 he left Germany, supposedly in the Netherlands. Indeed, traveled Hamburg to Britain, where he found a new job in 1941. Because of his unauthorized leave the Reich Education Ministry stopped the payment of his retirement benefits. From 1941 to 1947 he worked as a lecturer at University College, Southampton, University of Southampton later. In this time some friends, including the mathematician Margareth E. Grimshaw, who later served as a Fellow at Newnham College, Cambridge. In exile, his research interest now lay in other areas and problems of mathematics, he turned primarily algebraic and operator theoretical questions about. The New England experience was disappointing overall for hamburgers, because he could not find any reasonable position. The famous mathematician Godfrey Harold Hardy praised him in a letter as a mathematician and emphasized his refined and pleasant personality, but saw it as not very suitable, since he had no experience in the classroom for the envisaged temporary positions for emigrants as a mathematics teacher in secondary schools.

Work in Turkey and return to Germany

After the end of the "Third Reich" strove the Faculty of Arts in 1946 to his return. Hamburg said initially in autumn 1947 and raised in a letter dated October 18, 1947 at the Cologne Rector Josef Kroll entitled to his old chair, decided to but then for a visiting professorship at the University of Ankara, which he left to his leave on October 1. During the legal redress of National Socialist injustice made ​​him the North Rhine-Westphalian Minister of Education on August 11, 1953 a full professor of mathematics and director of the Mathematical Institute in Cologne, so that he could once again return to the University of Cologne as a full professor. For him, this was a special moment, as his " mathematical loyalty ," as expressed friends, even in exile was always Germany. This phase was of optimism and new plans coined. Already in the following year he accepted a visiting professorship at Cornell University in Ithaca (USA). He could contacts with American researchers, including tie to Arlen Brown and Shlomo Sternberg, with whom he planned joint publications and research papers.

However, his health was opposed new projects. Even his last years in Turkey were health under an unlucky star. In 1956 he married Vera Schereschewsky, but died a few months later on 14 August in Cologne.

An obituary of Hamburg, written by Margaret E. Grimshaw appeared in 1958 in the Journal of the London Mathematical Society. His estate to the widow handed over the first of the Mathematical Institute. From there he came in November 2007 in the University Archives Cologne (Access 689 - NL hamburger).

Work

In 1940 he broke the real - analytic case, a presumption of Constantin Caratheodory, where he worked since 1922 on every closed to the sphere homeomorphic ( at least twice differentiable ) surface in three-dimensional Euclidean space, there are at least two points where the surface is locally spherical ( umbilical points, both principal curvatures are equal there ). Examples are the sphere on which every point is umbilic, and the spheroid with only two umbilical points.

In 1921 he published a work on the identification of the Riemann zeta function by its functional equation, which was later taken up by Carl Ludwig Siegel and others.

Hamburger looked in his habilitation a generalization of the moment problem of Stieltjes Thomas. It asks whether and on what terms to a given sequence of real numbers is a Borel measure exists, the nth moments correspond to the respective sequence elements, the integration over the whole real axis and not only as the Stieltjes problem about the positive real axis.