**Cahit Arf** was a Turkish mathematician. He is known for the *Arf invariant* in topology.

- However, the Balkan War was fought by Serbia, Bulgaria, Greece, and Montenegro against the Ottoman Empire when Arf was two years old.
- Cahit Arf's interest in mathematics was stimulated during his school years in Izmir by a teacher who encouraged him to solve problems in euclidean geometry.
- Arf won a scholarship to continued his education in Paris and he returned to France, graduating from the École Normale Supérieure after spending two years there.
- Arf joined the Mathematics Department of Istanbul University.
- He completed his doctoral studies in 1938 obtaining, among other results, the theorem now known as the Hasse-Arf theorem.
- Arf returned from Germany to Istanbul University where he worked until 1962.
- In 1963 Arf taught at Robert College in Istanbul.
- Then, between 1964 and 1966, Arf worked at the Institute for Advanced Study at Princeton in the United States.
- Arf retired in 1980 and lived in Istanbul.
- Arf played a prominent role in establishing TUBITAK in 1971, the Scientific and Technical Research Council of Turkey.
- Arf received many awards and prizes for his outstanding contributions to mathematics and for his most distinguished career including the Inonu award.
- Arf contributed to the education of many of the present day mathematicians in Turkey, not only by his lectures but also through illuminating discussions in conferences and seminars.
- Those who had the opportunity to come into close contact with Arf, were deeply influenced by his sincere devotion to mathematics and to science in general.
- If one studies Cahit Arf's works, which are full of originality and painstaking computations, one will surely wonder where Professor Arf gets his inspirations, and how he gets insight into most complicated computations.
- Much of Arf's most important work was in algebraic number theory and he invented Arf invariants which have many applications in topology.
- His name is not only attached to Arf invariants but he is also remembered for the Hasse-Arf Theorem which plays an important role in class field theory and in Artin's theory of LLL-functions.
- In ring theory, Arf rings are named after him.
- In addition Arf worked in applied mathematics writing several papers on elastic plane bodies bounded by free boundaries and a paper on the algebraic structure of the cluster expansion in statistical mechanics.
- Arf presented a paper On a generalization of Green's formula and its application to the Cauchy problem for a hyperbolic equation to the volume Studies in mathematics and mechanics presented to Richard von Mises in 1954.
- Arf had met von Mises in 1933 in Istanbul.
- An International Symposium on Algebra and Number Theory was held in Arf's honour in Silivri from 3 to 7 September 1990.
- At an earlier conference on Rings and Geometry held in Istanbul in 1984, Arf had presented a paper The advantage of geometric concepts in mathematics.
- Arf died after a heart attack and was buried in Istanbul, following a ceremony at Istanbul University.

Born 11 October 1910, Salonika, Ottoman Empire (now Thessaloniki, Greece). Died 26 December 1997, Istanbul, Turkey.

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Origin Greece

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