Abraham Fraenkel (Hebrew: אברהם הלוי (אדולף) פרנקל; 17 February 1891 – 15 October 1965) was a German-born Israeli mathematician. He was an early Zionist and the first Dean of Mathematics at the Hebrew University of Jerusalem. He is known for his contributions to axiomatic set theory, especially his additions to Ernst Zermelo's axioms, which resulted in the Zermelo–Fraenkel set theory.
Abraham Adolf Halevi Fraenkel studied mathematics at the Ludwig-Maximilians-Universität München, the Friedrich Wilhelm University of Berlin, Marburg University, and he University of Breslau. After graduating, he lectured at the University of Marburg from 1916, and was promoted to professor in 1922.
In 1919, he married Wilhelmina Malka A. Prins (1892–1983). Due to the severe housing shortage in post-First World war Germany, for a few years the couple lived with fellow professor Kurt Hensel as subtenants.
After leaving Marburg University in 1928, Fraenkel taught at Kiel University for a year. He then made the choice of accepting a position at the Hebrew University of Jerusalem, which had been founded four years earlier, where he spent the rest of his career. He became the first dean of the faculty of mathematics, and for a while served as rector of the university.
On his final move to Palestine in 1933 (after losing his job in Germany due to the "Law for the Restoration of the Professional Civil Service"), Fraenkel changed his name from Adolf (Hitler's first name) to Abraham. He was a fervent Zionist and as such was a member of Jewish National Council and the Jewish Assembly of Representatives under the British mandate. He also belonged to the Mizrachi religious wing of Zionism, which promoted Jewish religious education and schools, and which advocated giving the Chief Rabbinate authority over marriage and divorce.
Fraenkel's early work was on Kurt Hensel's p-adic numbers and on the theory of rings. He is best known for his work on axiomatic set theory, publishing his first major work on the topic Einleitung in die Mengenlehre (Introduction to set theory) in 1919. In 1922 and 1925, he published two papers that sought to improve Zermelo's axiomatic system; the result is the Zermelo–Fraenkel axioms. Fraenkel worked in set theory and foundational mathematics.
Fraenkel was also interested in the history of mathematics, writing in 1920 and 1930 about Gauss's works in algebra, and he published a biography of Georg Cantor. After retiring from the Hebrew University and being succeeded by his former student Abraham Robinson, Fraenkel continued teaching at the Bar Ilan University in Ramat Gan (near Tel Aviv).
In 1956, Fraenkel was awarded the Israel Prize, for exact sciences.
1908. "Bestimmung des Datums des jüdischen Osterfestes für die Zeitrechnung der Mohammedaner". In Zeitschrift für Mathematik und naturwissenschaft Unterricht (39).
1909. "Eine Formel zur Verwandlung jüdischer Daten in mohammedanische". In Monatsschrift für Geschichte und Wissenschaft des Judentums, vol. 53, issue 11–12.
1910. "Die Berechnung des Osterfestes". Journal für die reine und angewandte Mathematik, vol 138.
"Über die Teiler der Null und die Zerlegung von Ringen". J. Reine Angew. Math. 145: 139–176. 1914. doi:10.1515/crll.1915.145.139.
1918. "Praktisches zur Universitätsgründung in Jerusalem". Der Jude 3:404–414.
1918b. "Mathematik und Apologie". Jeschurun, 5:112–126.
1919. Einleitung in die Mengenlehre. Berlin: Julius Springer.
1920. Materialien für eine wissenschaftliche Biographie von Gauss.
1921. "Die neueren Ideen zur Grundlagung der Analysis und Mengenlehre". In Jahresbericht der Deutschen Mathematiker-Vereinigung.
1922. "Axiomatische Begründung der transfiniten Kardinalzahlen I — Herrn K. Hensel zum sechzigsten Geburtstag". Mathematische Zeitschrift. 13: 153–188. 1922. doi:10.1007/bf01485286. S2CID 119960359.