Scholar of mathematics and physics
(B.11 October 1910, Kayalar / Thessaloniki – D.26 December 1997, Istanbul). He
is a worldwide famous mathematician and physicist who was raised in the Republican Period of Turkey. At the
age of two, his family settled to Istanbul since Thessaloniki came under
control of Greek army during the Balkan War. At the age of four he started
school in Istanbul. In 1919 at the age of nine he moved to Ankara with his
family. His family left here and returned to Istanbul for a short period and
then settled to Izmir. Cahit Arf’s interest in mathematics started in his Izmir
years. While in primary school he understood the geometric proof of Pythagorean
Theorem. Since the shape which was drawn for the evidence resembled the ears of
a donkey, old generations called this theorem “donkey’s theorem”. It is known
that his mathematics teacher encouraged Cahit Arf to solve questions from
Euclidean geometry during his education in Izmir.

In 1926 his
family decided that it was a more appropriate option for him to receive an
education a good education. Thus, Cahit Arf was sent to France for high school
education in 1926. After his high school education he completed in France, Ecole Normale Superieure in 1932 he wanted to be appointed teacher
in Kastamonu High School. However, with the help and direction of his
environment he served as a mathematics teacher in Galatasaray High School for a
while and later within the reform of universities in 1933 he was assigned as a
candidate associate professor to Istanbul University Faculty of Science.

Cahit Arf worked
together with his teacher Hasse to advance in his career at Göttingen
University in Germany, to where he was sent in 1937 to complete his PhD
program. As a result of this effort he completed his PhD thesis in 1938 which
also contained the famous result which is known as “Hasse-Arf Theorem” in
mathematics. In 1938, Cahit Arf essentially contributed to mathematics with his
studies in various fields such as algebra, number theory, theory of elasticity,
analysis, geometry and engineering mathematics and acquired structural and
permanent results. Upon the insist of Hasse he stayed for one more year in
Germany to continue his studies and meanwhile he discovered “Arf Invariants”
which was a great contribution to mathematics. His first scientific study was published
in a famous mathematics journal of Germany *“Crelle Journal”*in 1939.

After
returning to Turkey he became a professor in Istanbul University Faculty of
Science in 1943. Cahit Arf classified quadratic forms on objects whose
characteristics were two in a very skillful way. He built their invariants.
These invariants are known in the world literature as “Arf Invariants”. This
study of him was published in *“Crelle” *journal in 1944and introduced
Cahit Arf to the world. He was promoted to distinguished professorship in 1955 and
he worked in Istanbul University until 1962. In 1963 he started to give
mathematics lessons in Robert College. In 1964 he became President of the
Scientific Branch of Turkish Scientific and Technical Research Institution
(TÜBİTAK). In 1966 he went to United States of America and worked in
Universities of Princeton and California. In 1967 he returned to Turkey and
started to work at Middle Eastern Technical University. He played a very
effective role in the establishment of TÜBİTAK, Turkish Scientific and
Technical Research Institution. He took part in the establishment of Marmara
Research Center in Gebze.

Cahit Arf
retired in1980 from his duty at the university and
served in Gebze Research Center which is connected to TÜBİTAK. Between the
years 1985 and 1989 he presided Turkish Mathematics Association. He
inspired all Turkish mathematicians directly or indirectly, expanded the
horizons of all mathematicians around him with his warnings and ideas and made
it possible for them to direct their studies in a new perspective.

While working at the Middle East
Technical University he proved multiple times that he was not a scientist
detached from the world. It is known that Cahit Arf was reconciliatory but a
principled scientist who did not make concessions from his scientific
personality. With his studies about algebra he became famous in the whole
world. His studies about solubility of synthetic geometrical problems using a
ruler and compasses, and studies about invariants which appear during the
classification of quadratic forms of objects which are known after his name as
"Arf Invariant" or "Arf Rings", made him known among the
famous mathematicians in the world of mathematics. The formula of “Arf
Invariant” is as following: *arf (g)= ^{n }Sigma_{İ=1}
q(a;) q(b;)E Z_{2. }*Cahit Arf regarded mathematics not as a
profession but as a lifestyle. He always said to his students:

He introduced to the literature of mathematics not only with concepts of "Arf Rings”, “Arf Invariants” and “Arf Closure", but also theorems which are known as "Hasse-Arf Theorem". Cahit Arf, who entered the literature of world mathematics with his "Arf Theorem" and was accepted as “Einstein of Turkey”, is one of our rare talents who evaluated science who became a model for scientific and academic communities by using his research intelligence.

During the last years he studied
about the possible applications of mathematics within the science of biology.
In 1948 he received the İnönü Award. In 1974 he was granted the TÜBİTAK Science
Award, the Honorary PhD
by İTÜ and KTÜ in 1980 and the Honorary PhD by ODTÜ (METU) in 1981. At a young
age, he was chosen to Mainz Academy Informative Member and he became Honorary
Member of Turkish Sciences Academy. France presented him in 1994 “Commandeur des
Palmes Academique Prix”. In the words of Prof. Dr. Gündüz İkeda, a Turkish
mathematician with Japanese origin, *“Cahit Arf, is the most skillful
mathematician Turkey has had until now.” *In the backside of 10 Turkish
Lira, a portrait of Dist. Prof. Dr. Cahit Arf is present. Aside from a section
from Cahit Arf’s “Arf Invariant”, the backside of 10 Turkish Lira is filled
with elements such as “arithmetic series, abacus, digits which express binary
number system which indicate the digital system which is the basis of computer
technology”.

Besides
being the Pioneer of mathematics fort he last fifty years of our country, Cahit Arf became the “teacher of teachers” whom his
young colleagues approached for advice and experience and modeled his
determined and strong minded personality at hard times with his interest in
social problems, loyality to his country, sensitivity about the problems of the
university and education in general. He never abstained from saying clearly
what he knew as true. He wrote numerous articles about his field and held many
conferences at home and abroad. Cahit Arf also has a published book titled *‘Anlamak’
Tutkunu Bir Matematikçi* (common, 2006).