Editing Viggo Brun

{{Short description|Norwegian mathematician (1885–1978)}}{{Infobox scientist
| name              = Viggo Brun
| image             = Viggo Brun 1927-05-25.jpg
| birth_date        = 13 October 1885
| birth_place       = Lier, Norway
| death_date        = {{d-da|15 August 1978|13 October 1885}}
| death_place       = Drøbak, Norway
| citizenship       = Norway
| fields            = Number Theory
| known_for         = Brun's Theorem, Brun Sieve
}}

'''Viggo Brun''' (13 October 1885 &ndash; 15 August 1978) was a [[Norway|Norwegian]] professor, [[mathematician]] and [[Number theory|number theorist]].
<ref>{{cite web|url=   http://www.numbertheory.org/obituaries/OTHERS/brun/brun.html|title=     Viggo Brun|publisher =numbertheory.org  |date= 18 June 2003
|access-date= January 1, 2017 }}</ref>

==Contributions==
In 1915, he introduced a new method, based on [[Adrien-Marie Legendre|Legendre]]'s version of the [[sieve of Eratosthenes]], now known as the ''[[Brun sieve]]'', which addresses additive problems such as [[Goldbach's conjecture]] and the [[Twin prime|twin prime conjecture]]. He used it to prove that there exist infinitely many integers ''n'' such that ''n'' and ''n''+2 have at most nine [[prime factor]]s, and that all large even integers are the sum of two numbers with at most nine prime factors.<ref>{{cite web |author1=J J O'Connor |author2=E F Robertson |title=Viggo Brun |url=http://www-groups.dcs.st-and.ac.uk/history/Biographies/Brun.html |archive-url=https://web.archive.org/web/20170116172225/http://www-groups.dcs.st-and.ac.uk/history/Biographies/Brun.html |archive-date=2017-01-16 |access-date=January 1, 2017 |publisher=School of Mathematics and Statistics, University of St Andrews, Scotland}}</ref>

He also showed that the sum of the reciprocals of [[twin prime]]s converges to a finite value, now called [[Brun's constant]]: by contrast, [[Proof that the sum of the reciprocals of the primes diverges|the sum of the reciprocals of all primes is divergent]]. He developed a multi-dimensional [[continued fraction]] algorithm in 1919–1920 and applied this to problems in [[musical theory]]. He also served as [[praeses]] of the [[Royal Norwegian Society of Sciences and Letters]] in 1946.<ref name="tby">{{cite encyclopedia|year=1996|title=Vitenskapsselskapet|encyclopedia=Trondheim byleksikon|author=Bratberg, Terje|editor=Arntzen, Jon Gunnar|publisher=Kunnskapsforlaget|location=Oslo|pages=599–600|isbn=82-573-0642-8}}</ref>

==Biography==
Brun was born at Lier in [[Buskerud]], Norway. He studied at the [[University of Oslo]] and began research at the [[University of Göttingen]] in 1910.  In 1923, Brun became a professor at the [[File:ViggoBrun.jpg|thumb|Viggo Brun (published in 1911)]] [[Norwegian Institute of Technology|Technical University]] in Trondheim and in 1946 a professor at the [[University of Oslo]].<ref>{{cite web|url=   https://snl.no/Viggo_Brun|title=     Viggo Brun|publisher = Store norske leksikon|access-date= January 1, 2017 }}</ref>

He retired in 1955 at the age of 70 and died in 1978 (at 92 years-old) at [[Drøbak]] in [[Akershus]], Norway.<ref>{{cite web|url=   https://nbl.snl.no/Viggo_Brun
|title=     Viggo Brun|publisher = Norsk biografisk leksikon |author=  Bent Birkeland|access-date= January 1, 2017 }}</ref>

==See also==
* [[Brun's theorem]]
* [[Brun-Titchmarsh theorem]]
* [[Brun sieve]]
* [[Sieve theory]]


== Fotnoter ==
{{notelist}}


==References==
{{Reflist}}

==Other sources==
* [[Heini Halberstam|H. Halberstam]] and [[H. E. Richert]], ''Sieve methods'', Academic Press (1974) {{ISBN|0-12-318250-6}}.  ''Gives an account of Brun's sieve''.
* C.J. Scriba, ''Viggo Brun'', Historia Mathematica '''7''' (1980) 1–6.
* [http://www.numbertheory.org/obituaries/OTHERS/brun/ C.J. Scriba, ''Zur Erinnerung an Viggo Brun'', Mitt. Math. Ges. Hamburg '''11''' (1985) 271-290]

==External links==
*[https://web.archive.org/web/20030304091118/http://planetmath.org/encyclopedia/BrunsConstant.html Brun's Constant]
*[https://web.archive.org/web/20040604064319/http://planetmath.org/encyclopedia/BrunsPureSieve.html Brun's Pure Sieve]
* [http://arkivportalen.no/side/arkiv/detaljer?arkivId=no-NTNU_arkiv000000061437 Viggo Brun personal archive] exists at NTN University Library [https://www.ntnu.no/ub/bibliotek/dora Dorabiblioteket]
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{{s-bef|before=[[Ragnvald Iversen]]}} 
{{s-ttl|title=Praeses of the [[Royal Norwegian Society of Sciences and Letters]]|years=1946}} 
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{{DEFAULTSORT:Brun, Viggo}}
[[Category:1885 births]]
[[Category:1978 deaths]]
[[Category:People from Lier, Norway]]
[[Category:Norwegian mathematicians]]
[[Category:20th-century Norwegian mathematicians]]
[[Category:Number theorists]]
[[Category:University of Oslo alumni]]
[[Category:Academic staff of the Norwegian Institute of Technology]]
[[Category:Academic staff of the University of Oslo]]
[[Category:Royal Norwegian Society of Sciences and Letters]]
[[Category:People from Frogn]]
[[Category:Presidents of the Norwegian Mathematical Society]]