# Abraham Plessner

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**Abraham Plessner** (February 13, 1900 – April 18, 1961) was a Russian mathematician. He was born on February 13, 1900, to a Jewish family in [Łódź](/source/%C5%81%C3%B3d%C5%BA), which is now in [Poland](/source/Poland). He studied at secondary school where he was taught in Russian, German, and Polish. He studied at the University of Giessen where he studied under [Ludwig Schlesinger](/source/Ludwig_Schlesinger) and [Friedrich Engel](/source/Friedrich_Engel_(mathematician)). He also studied at the [University of Göttingen](/source/University_of_G%C3%B6ttingen) and Berlin. He completed his doctorate from the [University of Giessen](/source/University_of_Giessen) in 1922. Jointly with [Kurt Hensel](/source/Kurt_Hensel) he edited [Kronecker](/source/Leopold_Kronecker)'s collected works.

After completing his doctorate, Plessner worked in [Marburg](/source/Marburg) where he published a paper containing what is now called [Plessner's theorem](/source/Plessner's_theorem). It is a theorem concerning the boundary behaviour of functions meromorphic in the unit disk.

Plessner submitted his habilitation, the extra post-doctoral qualification needed to lecture at a German university, to the faculty at the University of Giessen. He was denied because he happened to be a Russian citizen. He then moved to Moscow and joined the research group of [Nikolai Nikolaevich Luzin](/source/Nikolai_Nikolaevich_Luzin) at [Moscow State University](/source/Moscow_State_University). Though he left Germany before the [Nazi's seized power](/source/The_Enabling_Act_of_1933) in 1933, some scholars consider him an early Jewish emigrant from Nazi Germany; his career was negatively impacted by anti-semitism and he was not able to return to Germany, unlike early non-Jewish emigrants such as [Eberhard Hopf](/source/Eberhard_Hopf) and Wilhelm Maier. One scholar writes that in Plessner's case "the anti-Semitic prejudice was mixed with and partly hidden by concern for their lack of a German citizenship".[1][2]

In 1939, he became a professor at [Moscow State University](/source/Moscow_State_University). He also held a position at the Mathematical Institute of the USSR Academy of Sciences. In 1949, he was dismissed from both posts during the Soviet campaign against ["rootless cosmopolitans"](/source/Rootless_cosmopolitan).

Plessner is widely viewed as a founder of the Moscow school of [functional analysis](/source/Functional_analysis). He faced financial and health problems in his later years. He died on April 18, 1961, in Moscow.

## References

1. Siegmund-Schultze, Reinhard (2009). [*Mathematicians Fleeing from Nazi Germany: Individual Fates and Global Impact*](https://books.google.com/books?id=jBoEmGB3B3MC). Princeton University Press. p. 8. ISBN 978-0-691-12593-0.

1. Pinl, Max & Furtmüller, Lux (1973). "Mathematicians under Hitler". *The Leo Baeck Institute Year Book*. **18** (1). [doi:10.1093/leobaeck/20.1.370](https://doi.org/10.1093/leobaeck/20.1.370)

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