Hans Hamburger

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

education and study

His parents' home was middle class. His father Karl Hamburger was a lawyer, he worked as a lawyer and notary in Berlin . His mother Margarete Hamburger was born Levy. Hamburger attended the French grammar school in Berlin. From 1907 to 1914 Hans Hamburger studied in Berlin, Lausanne and Göttingen as well as with Alfred Pringsheim in Munich , where he received his doctorate in 1914 with a thesis "On the integration of linear homogeneous differential equations".

After serving as a soldier in the First World War from 1915 to 1918 , he completed his habilitation at the University of Berlin with the work "Extensions of the Stieltjes'schen Moments Problem", which appeared as a report from the Bavarian Academy of Sciences . In Berlin he worked first as a private lecturer and from 1922 as an associate professor.

Years in Cologne and emigration

In 1924, Hamburger followed a call to Cologne as a full professor to the 2nd Mathematical Chair and Director of the Mathematical Institute (alongside Ernst Sigismund Fischer ). In 1927 he married Malla Jessen. The marriage was later divorced. During his time in Cologne, he was mainly concerned with problems of differential geometry, such as the Caratheodory hypothesis, on which he published variously, and which he solved in the real-analytical case.

In 1935 the National Socialists withdrew his venia legendi , which meant the end of his work at the Mathematical Institute in Cologne. He then moved to Berlin with his mother. In 1939 he left Germany, supposedly for the Netherlands. In fact, Hamburger traveled to Great Britain , where he found a new job in 1941. Because of his unauthorized departure, the Reich Ministry of Education stopped paying his retirement benefits. From 1941 to 1947 he worked as a lecturer at University College in Southampton, later the University of Southampton . During this time, some friendships developed, including with the mathematician Margareth E. Grimshaw , who later worked as a fellow at Newnham College in Cambridge. In exile, his research interests focused on other areas and problems of mathematics ; he mainly turned to algebraic and operator-theoretical questions. Overall, the England experience was disappointing for Hamburger, as he could not find a suitable position. The famous mathematician Godfrey Harold Hardy praised him in a letter as a mathematician and emphasized his cultured and pleasant personality, but saw him as unsuitable for the proposed temporary positions for emigrants as a mathematics teacher in high schools, since he had no experience in school teaching .

Work in Turkey and return to Germany

After the end of the “ Third Reich ”, the Faculty of Philosophy tried to get him back in 1946. Hamburger said initially the fall of 1947 and raised in a letter of 18 October 1947 at the Cologne Rector Josef Kroll entitled to his old chair, but then opted for a visiting professor at the University of Ankara , which he took leave on October 1 . In the course of the legal reparation for National Socialist injustice, the North Rhine-Westphalian minister of education appointed him again as full professor for mathematics and director of the Mathematical Institute in Cologne on August 11, 1953, so that he could return to the University of Cologne as full professor . This was a special moment for him, as his “mathematical loyalty”, as friends put it, was always applied to Germany, even in exile. This phase was marked by optimism and new plans. In the following year he already held a visiting professorship at Cornell University in Ithaca (USA). He was able to establish contacts with American researchers, including Arlen Brown and Shlomo Sternberg , with whom he planned joint publications and research work.

His health condition, however, prevented new projects. His last years in Turkey were already badly health-wise. In 1956 he married Vera Schereschewsky , but died a few months later on August 14th in Cologne .

An obituary for Hamburger by Margaret E. Grimshaw appeared in the Journal of the London Mathematical Society in 1958 . The widow first gave his estate to the Mathematical Institute. From there it was transferred to the Cologne University Archives in November 2007 (access 689 - Hamburg branch).

plant

In 1940, in a real-analytical case, he solved a conjecture of Constantin Caratheodory , on which he had been working since 1922: on every closed surface that is homeomorphic to the sphere (at least two-fold differentiable) in three-dimensional Euclidean space there are at least two points at which the surface is locally spherical ( Umbilical points , both main curves are the same there). Examples are the sphere on which every point is an umbilical point and the ellipsoid of revolution with only two umbilical points.

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

In his habilitation, Hamburger considered a generalization of the moment problem by Thomas Stieltjes . It asks whether and under what conditions a Borel measure exists for a given sequence of real numbers, the nth moments of which correspond to the respective terms of the sequence, whereby the integration over the entire real axis and not just over the positive one, as in the Stieltjes problem real axis takes place.

literature

  • F. Golczewski Cologne University Teacher and National Socialism. Approaches to the history of persons , Vienna, Cologne: Böhlau 1988
  • Margarete E. Grimshaw: Hans Ludwig Hamburger . In: Journal of the London Mathematical Society 33 (1958), pp. 377-383

Web links

Individual evidence

  1. ↑ Hamburger About the integration of linear homogeneous differential equations , dissertation  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / gdz.sub.uni-goettingen.de  
  2. ↑ Reinhard Siegmund-Schultze Mathematicians fleeing from Nazi Germany , Princeton University Press 2009, p. 118, Hardy's letter from 1940
  3. ↑ Siegmund-Schultze, loc. cit., p. 324
  4. ^ Proof of a Conjecture of Caratheodory Part 1 to 3, Annals of Mathematics, Volume 41, 1940, p. 63, Acta Mathematica, Volume 73, 1941, pp. 175, 229. This was preceded by Hamburger Ein Satz about curve networks on closed surfaces , Session reports of the Prussian Academy of Sciences, Volume 21, 1922, pp. 258–262, About curve networks with isolated singularities on solid surfaces , Mathematische Zeitschrift, Volume 19, 1924, pp. 50–66. A simplified proof, which later turned out to be incomplete, was published by Gerrit Bol in 1944 (Math. Zeitschrift Volume 49, p. 389).
  5. ^ Hamburger On the Riemann functional equation of the zeta function , Part 1 : Math. Journal, Volume 10, 1921, pp. 240-254. Part 2 : Math. Journal, Volume 11, 1921, p. 224, Part 3 : Math. Journal, Volume 13, 1922, p. 283
  6. ↑ Hamburger on an extension of the Stieltjesches moment problem, Mathematische Annalen, Volume 81, 1920, p.235 , part 2, Volume 82, 1920, p. 120, part 3, ibid p. 168. As well as announcement in session reports Bayr. Academy of Sciences 1919
personal data
SURNAME Hamburger, Hans
ALTERNATIVE NAMES Hamburger, Hans Ludwig (full name)
BRIEF DESCRIPTION German mathematician
DATE OF BIRTH August 5, 1889
PLACE OF BIRTH Berlin
DATE OF DEATH August 14, 1956
Place of death Cologne