Editing Cahit Arf

{{Short description|Turkish mathematician (1910–1997)}}
{{Infobox scientist
| name              = Cahit Arf
| image             = Cahit Arf.jpg
| image_size        = 240px
| caption           = <!--  Cahit Arf, probably in front of [[Middle East Technical University|METU]] Department of Mathematics. -->
| birth_date        = {{Birth date|1910|10|24|df=y}}
| birth_place       = [[Thessaloniki]], [[Ottoman Empire]]
| nationality       = [[Turkey|Turkish]]
| death_date        = {{death date and age|1997|12|26|1910|10|24|df=y}}
| death_place       = [[Bebek, Istanbul|Bebek]], [[Istanbul]], [[Turkey]]
| field             = [[Mathematics]]
| workplaces        = {{Bulleted list |[[Galatasaray High School]] |[[Istanbul University]] |[[Boğaziçi University|Robert College]] |[[University of California, Berkeley]] |[[Middle East Technical University]] |[[Scientific and Technological Research Council of Turkey]] }}
| alma_mater        = {{Bulleted list |[[École Normale Supérieure]] |[[University of Göttingen]] }}
| doctoral_advisor  = [[Helmut Hasse]]
| known_for         = *[[Hasse–Arf theorem]]
* [[Arf invariant]]
* [[Arf semigroup]]
* [[Arf ring]]
| footnotes         = 
}}
'''Cahit Arf''' ({{IPA|tr|dʒaːhit aɾf|lang}}; 24 October 1910 &ndash; 26 December 1997) was a [[Turkish people|Turkish]] [[mathematician]]. He is known for the [[Arf invariant]] of a [[quadratic form]] in [[characteristic (algebra)|characteristic]] 2 (applied in [[knot theory]]  and [[surgery theory]]) in  [[topology]], the [[Hasse&ndash;Arf theorem]] in [[ramification theory]], [[Arf semigroup]]s and [[Arf ring]]s.

==Biography==
Cahit Arf was born on 11 October 1910<ref>[http://turnbull.mcs.st-and.ac.uk/history/Biographies/Arf.html Cahit Arf] {{Webarchive|url=https://web.archive.org/web/20160304114455/http://turnbull.mcs.st-and.ac.uk/history/Biographies/Arf.html |date=2016-03-04 }}, by J.J. O'Connor and E.F. Robertson, at MacTutor History of Mathematics Archive</ref> in [[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 [[İzmir]] 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 [[École Normale Supérieure]].

Returning to Turkey, he taught [[mathematics]] at [[Galatasaray High School]]. In 1933 he joined the Mathematics Department of [[Istanbul University]]. In 1937 he went to [[Göttingen]], where he received his PhD from the [[University of Göttingen]] and worked with [[Helmut Hasse]] and Josue Cruz de Munoz. He returned to Istanbul University and worked there until his involvement with the foundation work of the [[Scientific and Technological Research Council of Turkey|Scientific and Technological Research Council]] (TÜBİTAK) upon President [[Cemal Gürsel]]'s appointment in 1962. After serving as the founding director of the council in 1963, he joined the Mathematics Department of [[Robert College]] in Istanbul. Arf spent the period of 1964&ndash;1966 working at the [[Institute for Advanced Study]] in [[Princeton, New Jersey]].<ref>[http://www.ias.edu/people/cos/frontpage?page=4 Institute for Advanced Study: A Community of Scholars] {{webarchive|url=https://web.archive.org/web/20130106144338/http://www.ias.edu/people/cos/frontpage?page=4 |date=2013-01-06 }}</ref> He later visited [[University of California, Berkeley]] for one year.

Upon his final return to Turkey, he joined the Mathematics Department of the [[Middle East Technical University]] and continued his studies there until his retirement in 1980. Arf received numerous awards for his contributions to mathematics, among them are: İnönü Award in 1948, Scientific and Technological Research Council of Turkey (TÜBİTAK) Science Award in 1974, and [[Commandeur des Palmes Academiques]] (France) in 1994. 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. Arf died on December 26, 1997, in [[Bebek, Istanbul|Bebek]], Istanbul, at the age of 87. His collected works were published, in 1988, by the [[Turkish Mathematical Society]].

==Influence==
[[File:10 Türk Lirası reverse.jpg|thumb|Reverse of the 10 lira banknote (2009)]]
[[File:Gravestone of Cahit Arf.jpg|thumb|Gravestone of Cahit Arf, [[Zincirlikuyu Cemetery]], Istanbul]]
Arf's influence on science in general and mathematics in particular was profound. Although he had very few formal students, many of the mathematicians of Turkey, at some time of their careers, had fruitful discussions on their field of interest with him and had received support and encouragement.

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-function]]s.

Arf's portrait is depicted on the [[Obverse and reverse|reverse]] of the Turkish 10 [[Turkish lira|lira]] banknote issued in 2009.<ref>[http://www.tcmb.gov.tr/yeni/eng/ Central Bank of the Republic of Turkey] {{Webarchive|url=https://web.archive.org/web/20090615060512/http://www.tcmb.gov.tr/yeni/eng/ |date=2009-06-15 }}. Banknote Museum: [http://www.tcmb.gov.tr/yeni/banknote/E9/10tle.htm 9. Emission Group &ndash; Ten Turkish Lira &ndash; I. Series] {{webarchive|url=https://web.archive.org/web/20090510005819/http://www.tcmb.gov.tr/yeni/banknote/E9/10tle.htm |date=2009-05-10 }}. – Retrieved on 20 April 2009.</ref>

[[Middle East Technical University]] [http://www.math.metu.edu.tr/ Department of Mathematics] organizes a special lecture session called the Cahit Arf lecture each year in  memory of Arf.

==Legacy==
Since 2001, the '''Arf lectures''' in honor of Cahit Arf have been held annually at the '''Cahit Arf Auditorium''' in the Department of Mathematics of [[Middle East Technical University]].<ref>{{cite web|url=https://math.metu.edu.tr/en/arf-lectures|title=Arf Lectures|publisher=[[Middle East Technical University]]|access-date=3 March 2020}}</ref>  Each lecture is presented by a distinguished mathematician selected by the advisory board. Since 2006, the Arf Lecturers are invited to deliver their talks at [[IMBM |Istanbul Center for Mathematical Sciences]] (IMBM),  too. 
* 2022: [[Andrew Sutherland (mathematician)|Andrew Sutherland]] of the [[Massachusetts Institute of Technology]]
* 2019: [[Geordie Williamson]] of [[The University of Sydney]]
* 2018: [[Fernando Rodriguez Villegas]] of The Abdus Salam [[International Centre for Theoretical Physics]]
* 2015: [[Vladimir Voevodsky]] of [[Institute for Advanced Study, Princeton]]
* 2013/14: [[Persi Diaconis]] of [[Stanford University]]
* 2012: [[David Nadler (mathematician)|David Nadler]] of [[Northwestern University]] and [[University of California, Berkeley]]
* 2011: [[Jonathan Pila]] of [[University of Oxford]]
* 2010: [[John Morgan (mathematician)|John W Morgan]] of [[Simons Center for Geometry and Physics]] at [[Stony Brook University]]
* 2009: [[Ben Joseph Green]] of [[University of Cambridge]]
* 2008: [[Günter Harder]] of [[University of Bonn|Mathematisches Institut der Universitat Bonn]] and [[Max Planck Institute for Mathematics]]
* 2007: [[Hendrik Lenstra]] of [[Universiteit Leiden]] Mathematisch Instituut
* 2006: [[Jean-Pierre Serre]] of [[Collège de France]]
* 2005: [[Peter Sarnak]] of [[Princeton University]] and the [[Institute for Advanced Study, Princeton]]
* 2004: [[Robert Langlands]] of the [[Institute for Advanced Study, Princeton]]
* 2003: [[David Mumford]] of [[Brown University]] Division of Applied Mathematics
* 2002: [[Don Zagier]] of [[University of Utrecht]] / [[Collège de France]]
* 2001: [[Gerhard Frey]] of [[University of Essen]] Institute for Experimental Mathematics

==See also==
* [[Hasse–Arf theorem]]
* [[Arf invariant]]
* [[Arf semigroup]]
* [[Arf ring]]

==Notes==
{{Reflist}}

==References==
*{{citation |title=The collected papers of Cahit Arf |first=Cahit |last=Arf |publisher=Turkish Mathematical Society |year=1990 |url=http://www.math.metu.edu.tr/cahitarf/collected.html |url-status=dead |archiveurl=https://web.archive.org/web/20090501051313/http://math.metu.edu.tr/cahitarf/collected.html |archivedate=2009-05-01 }}
*{{Citation | last1=Ikeda | first1=Masatoshi G. | title=Cahit Arf's contribution to algebraic number theory and related fields | url=http://mistug.tubitak.gov.tr/bdyim/toc.php?dergi=mat&yilsayi=1998/1 | mr=1631730 | year=1998 | journal=Turkish Journal of Mathematics | issn=1300-0098 | volume=22 | issue=1 | pages=1–14 | url-status=dead | archiveurl=https://web.archive.org/web/20110822060705/http://mistug.tubitak.gov.tr/bdyim/toc.php?dergi=mat&yilsayi=1998%2F1 | archivedate=2011-08-22 }}
*{{citation |title= A scientific biography of Cahit Arf (1910-1997)|first1=Ali Sinan |last1=Sertöz |date=16 January 2013 | arxiv=1301.3699|bibcode=2013arXiv1301.3699S}}
*{{citation |title=Anlamak tutkunu bir matematikçi: Cahit Arf |first1=Tosun |last1=Terzioğlu |first2=A.  |last2=Yılmaz|publisher=TÜBA |year=2005}}

==Further reading==
* {{citation | last=Roquette | first=Peter | authorlink=Peter Roquette | title=Contributions to the history of number theory in the 20th century | zbl=1276.11001 | series=Heritage of European Mathematics | location=Zürich | publisher=[[European Mathematical Society]] | isbn=978-3-03719-113-2 | year=2013 | chapter=Cahit Arf and his invariant | pages=189–222 }}

==External links==
{{Commons}}
* [https://math.metu.edu.tr/en/arf-lectures Cahit Arf Lectures homepage]
* [https://math.metu.edu.tr/en/cahit-arf Page and links on Cahit Arf]
* [http://www.turkmath.org/beta/cahitarf.php A documentary on Cahit Arf]
* {{MacTutor Biography|id=Arf}}
* {{MathGenealogy|id=26096}}
* [https://zbmath.org/authors/?q=ai:arf.cahit Author profile] in the database [[Zentralblatt MATH|zbMATH]]

{{Authority control}}

{{DEFAULTSORT:Arf, Cahit}}
[[Category:1910 births]]
[[Category:1997 deaths]]
[[Category:Scientists from Thessaloniki]]
[[Category:People from Salonica vilayet]]
[[Category:Macedonian Turks]]
[[Category:20th-century Turkish mathematicians]]
[[Category:Topologists]]
[[Category:École Normale Supérieure alumni]]
[[Category:Academic staff of Istanbul University]]
[[Category:Institute for Advanced Study visiting scholars]]
[[Category:University of Göttingen alumni]]
[[Category:Academic staff of Middle East Technical University]]
[[Category:Commandeurs of the Ordre des Palmes Académiques]]
[[Category:Recipients of TÜBİTAK Science Award]]
[[Category:METU Mustafa Parlar Foundation Science Award winners]]