**Stefan Cohn-Vossen** was a mathematician, born in what is now Poland, who is known for his collaboration with David Hilbert on a geometry book.

- Stefan was brought up and educated in Breslau.
- The city of around 500,000 inhabitants was, by the time that Cohn-Vossen was growing up there, largely German due chancellor Otto von Bismarck's efforts to Germanize the area.
- Cohn-Vossen attended Breslau University and his thesis advisor there was Adolf Kneser.
- In 1930 Cohn-Vossen was appointed as a privatdocent at the University of Cologne.
- An anti-Semitic campaign led to increased support for the Nazis but Jews like Cohn-Vossen had increasing cause to fear the direction in which the country was moving.
- Cohn-Vossen was dismissed from his teaching position at the University of Cologne.
- During the three years that Cohn-Vossen had spent in Cologne he had become well-known with the publication in 1932 of the book Anschauliche Geometrie Ⓣ(Descriptive geometry) which was a joint work with David Hilbert.
- The book was based on lectures that Hilbert had given at Göttingen in 1921 but making this course into a book had been Cohn-Vossen's task.
- The book was of great importance but this presented problems to the Nazis who had dismissed Cohn-Vossen from his post because of his race.
- The way that they overcame the difficult conflict between mathematical quality and anti-Semitism was to reduce the role of Cohn-Vossen to that of an amanuensis.
- Ludwig Bieberbach, who allowed Nazi ideology to completely override his mathematical judgement, took care to emphasise that his only citations to Anschauliche Geometrie were those that were ascribable solely to Hilbert and definitely not Cohn-Vossen.
- brilliant intuitive and concrete approach to geometry provided by Hilbert and his collaborator Cohn-Vossen ...
- After Cohn-Vossen was dismissed from his position at the University of Cologne in 1933 he left Germany and went to Switzerland.
- Cohn-Vossen had been appointed as a professor at Leningrad University in 1935, working at the Steklov Mathematical Institute of the USSR Academy of Sciences.
- The Steklov Mathematical Institute moved to Moscow in the following year and Cohn-Vossen moved with the Institute - again he was appointed as a professor at the University in Moscow.
- The importance of this work to the Russian school is seen from the fact that in 1959 a 303-page Russian book Some problems of differential geometry in the large (Russian) was published containing Russian translation of seven of Cohn-Vossen's papers.
- The book contained a survey by Nikolai Vladimirovich Efimov putting Cohn-Vossen's papers into their historical context.
- Cohn-Vossen's investigated whether general convex surfaces are uniquely determined by their metric.

Born 28 May 1902, Breslau, Germany, now Wrocław, Poland. Died 25 June 1936, Moscow, Russia.

View full biography at MacTutor

Origin Poland

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