# Cahit Arf

**Cahit Arf** (October 11, 1910 - December 26, 1997) was a Turkish mathematician. He is known for the Arf invariant of a quadratic form in characteristic 2 (applied in knot theory and surgery theory) in topology, the Hasse-Arf theorem in ramification theory, and Arf rings. He facilitated the now-celebrated visit of Robert Langlands to Turkey (now famous for the Langlands program, among many other things); during which Langlands worked out some arduous calculations on the epsilon factors of Artin L-functions.

## Biography

Cahit Arf was born on October 11, 1910 in Selanik (Thessaloniki), which was then a part of the Ottoman Empire. His family migrated to Istanbul with the outbreak of the Balkan War in 1912. The family finally settled in Izmir where Cahit Arf received his primary education. Upon receiving a scholarship from the Turkish Ministry of Education he continued his education in Paris and graduated from Ecole Normale Superieure.

Returning to Turkey, he taught mathematics at Galatasaray Lisesi. In 1933 he joined the Mathematics Department of Istanbul University. In 1937 he went to Gottingen, where he received his PhD from the University of Göttingen and he worked with Helmut Hasse. He returned to Istanbul University and worked there till 1962 and then joined the Mathematics Department of Robert College in Istanbul. Professor Arf was at the Institute for Advanced Study in Princeton during 1964 - 1966. Later he visited University of California, Berkeley for one year.

Upon returning to Turkey he joined the Mathematics Department of the Middle East Technical University and in 1980 he retired from this university. Professor Arf received several awards for his contributions to Mathematics, among them are, Inonu Award 1948, Scientific and Technological Research Council of Turkey (TUBITAK) Science Award 1974, Comandur des Palmes Academiques 1994. Professor Arf was a member of the Mainz Academy and the Turkish Academy of Sciences. He was the president of the Turkish Mathematical Society from 1985 until 1989. Cahit Arf passed away on December 26, 1997 in Bebek, Istanbul, at the age of 87. The collected works of Cahit Arf was published, in 1988, by the Turkish Mathematical Society.

## Influence

Professor Arf's influence on Turkish Mathematics was profound. Although he had very few formal students, almost all of the present day active mathematicians of Turkey, at some time of their carrier, had fruitful discussions on their field of interest with him and had received support and encouragement.

Cahit Arf is regarded as the greatest Turkish mathematician of the twentieth century (the runner-up for the title could be Selman Akbulut).

See also: List of Turkish scientists

## Cahit Arf Lectures

Middle East Technical University Department of Mathematics organizes a special lecture session each year in the name and memory of Cahit Arf. Previous lecturers include:

**2004**: Robert Langlands of Princeton Institute for Advanced Study**2003**: David Mumford of Brown University Division of Applied Mathematics**2002**: Don Zagier of University of Utrecht / Collége de France**2001**: Gerhard Frey of University of Essen Institute for Experimental Mathematics