**Helmut Hasse** did fundamental work in algebra and number theory. He is e.g. known for Hasse diagrams.

- Helmut studied for two years at the Fichte-Gymnasium in Berlin before volunteering for naval service during World War I.
- In the academic year 1917/18 Hasse was stationed at Kiel on his naval duties and he was able to attend the lectures of Otto Toeplitz.
- He was most influenced by Hecke despite the fact that Hecke left Göttingen to take up an appointment in Hamburg only a few months after Hasse arrived in Göttingen.
- It might be supposed that Hasse would have followed Hecke to Hamburg but he did not take this route, going to study under Hensel at Marburg in 1920.
- Hensel's work on ppp-adic numbers was to have a major influence on the direction of Hasse's research.
- In October 1920 Hasse discovered the 'local-global' principle which shows that a quadratic form that represents 0 non-trivially over the ppp-adic numbers for each prime ppp, and over the real numbers, represents 0 non-trivially over the rationals.
- The importance of this result, now known as the Hasse principle, is that both the representability of a number by a given form and whether two forms are equivalent can be decided using only local information.
- In 1922 Hasse was appointed a lecturer at the University of Kiel, then three years later he was appointed professor at Halle.
- During his time at Kiel, Hasse kept in close contact with the mathematicians at Hamburg including Artin, Hecke, Ostrowski and Schreier.
- At Halle Hasse obtained fundamental results on the structure of central simple algebras over local fields.
- In 1930 Hensel retired from Marburg and Hasse was appointed to fill his chair.
- The year 1933 was to be significant for all of Germany and for Hasse in particular.
- When Weyl resigned from his professorship in Göttingen, Hasse received an offer as his successor.
- At one point, Hasse hoped to increase his influence with the authorities and so he applied for membership in the Nazi Party.
- But one of Hasse's antecendents was a Jew and, therefore, membership was not granted.
- From 1939 until 1945 Hasse was on war leave from Göttingen and he returned to naval duty, working in Berlin on problems in ballistics.
- In May 1949, Hasse was appointed professor at the Humboldt University in East Berlin.
- In 1950 Hasse was appointed to Hamburg where he continued to teach until he retired in 1966.
- This reference to editorial work is made because Hasse was editor of Crelle's Journal for 50 years.
- Hasse was honoured by many organisations during his life.

Born 25 August 1898, Kassel, Germany. Died 26 December 1979, Ahrensburg (near Hamburg), Germany.

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Origin Germany

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