Editing Felix Hausdorff (section)

===Under the Nazi dictatorship and suicide===
After the takeover by the [[National Socialist]] party, [[anti-Semitism|antisemitism]] became state doctrine. Hausdorff was not initially concerned by the "[[Law for the Restoration of the Professional Civil Service]]", adopted in 1933, because he had been a German public servant since before 1914. However, he was not completely spared, as one of his lectures was interrupted by National Socialist student officials. In the winter semester of 1934/1935, there was a working session of the National Socialist German Student Union (NSDStB) at the University of Bonn, which chose "Race and Ethnicity" as their theme for the semester. Hausdorff cancelled his 1934/1935 winter semester Calculus III course on 20 November, and it is assumed that the choice of theme was related to the cancellation of Hausdorff's class, since in his long career as a university lecturer he had always taught his courses through to their end.

On March 31, 1935, after some back and forth, Hausdorff was finally given emeritus status. No words of thanks were given for his 40 years of successful work in the German higher education system.

His [[Nachlass|academic legacy]] shows that Hausdorff was still working mathematically during these increasingly difficult times, and continued to follow current developments of interest. 
He wrote, in addition to the expanded edition of his work on set theory, seven works on topology and descriptive set theory. These were published in Polish magazines: one in ''[[Studia Mathematica]]'', the others in ''[[Fundamenta Mathematicae]]''.
He was supported at this time by [[Erich Bessel-Hagen]], a loyal friend to the Hausdorff family who obtained books and magazines from the academic library, which Hausdorff was no longer allowed to enter.

A great deal is known about the humiliations to which Hausdorff and his family especially were exposed to after [[Kristallnacht]] in 1938. There are many sources, including the letters of Bessel-Hagen.<ref>Neuenschwander, E.: ''Felix Hausdorffs letzte Lebensjahre nach Dokumenten aus dem Bessel-Hagen-Nachlaß''. In: Brieskorn 1996, S.&nbsp;253–270.</ref>

[[File:Abschiedsbrief Felix Hausdorffs – Seite 1.png|thumb|The first page of his farewell letter to Hans Wollstein]]

In 1939, Hausdorff asked the mathematician [[Richard Courant]], in vain, for a research fellowship to be able to emigrate into the USA. 
In mid-1941, the Bonn Jews began to be deported to the "Monastery for Eternal Adoration" in [[Endenich]], [[Bonn]], from which the nuns had been expelled. Transports to death camps in the east occurred later. After Hausdorff, his wife, and his wife's sister, Edith Pappenheim (who was living with them), were ordered in January 1942 to move to the Endenich camp, the three died by suicide on 26 January 1942 by taking an overdose of [[veronal]].<ref>Schubring, G. (2021). Biographie. Felix Hausdorff, Gesammelte Werke. Band IB. by Egbert Brieskorn and Walter Purkert. Math Intelligencer 43, 94–98</ref> Their final resting place is located on the cemetery [[Poppelsdorf]] in Bonn. In the time between their placement in temporary camps and his suicide, he gave his handwritten ''[[Nachlass]]'' to the Egyptologist and presbyter [[Hans Bonnet]], who saved as much of them as possible, even despite the destruction of his house by a bomb.

Some of his fellow Jews may have had illusions about the camp Endenich, but not Hausdorff. In the estate of Bessel-Hagen, E. Neuenschwander discovered the farewell letter that Hausdorff wrote to his lawyer Hans Wollstein, who was also Jewish.<ref>Nachlass Bessel-Hagen, Universitätsarchiv Bonn. Abgedruckt in Brieskorn 1996, S.&nbsp;263–264 und im Faksimile S.&nbsp;265–267</ref><ref>{{Wikisource-inline|de:Abschiedsbrief Felix Hausdorffs|Abschiedsbrief Felix Hausdorffs|single=true}}</ref> Here is the beginning and end of the letter:

[[File:Hausdorff-Grab.jpg|thumb|Hausdorff's gravestone in Bonn-[[Poppelsdorf]]]]

{{blockquote|Dear friend Wollstein!

If you receive these lines, we (three) have solved the problem in a different manner — in the manner of which you have constantly tried to dissuade us. The feeling of security that you have predicted for us once we would overcome the difficulties of the move, is still eluding us; on the contrary, Endenich may not even be the end!

What has happened in recent months against the Jews evokes justified fear that they will not let us live to see a more bearable situation.}}

After thanking friends and, in great composure, expressing his last wishes regarding his funeral and his will, Hausdorff writes:

{{blockquote|I am sorry that we cause you yet more effort beyond death, and I am convinced that you are doing what you <u>can</u> do (which perhaps is not very much). Forgive us our desertion! We wish you and all our friends to experience better times.

Your truly devoted

Felix Hausdorff}}

Unfortunately, this desire was not fulfilled. Hausdorff's lawyer, Wollstein, was murdered in [[Auschwitz]].

[[File:Hausdorff-strasse.jpg|thumb|Hausdorffstraße (Bonn)]]

Hausdorff's library was sold by his son-in-law and sole heir, Arthur König. The portions of Hausdorff's ''[[Nachlass]]'' which could be saved by Hans Bonnet are now in the university and State Library of Bonn. The ''Nachlass'' is catalogued.<ref>Siehe Findbuch Nachlass Hausdorff</ref>