Editing Karol Borsuk

{{Short description|Polish mathematician (1905–1982)}}
{{Infobox scientist
|name              = Karol Borsuk
|image             = Karol Borsuk, matematyk.jpg
|image_size        =
|caption           = 
|birth_date        = {{birth date|1905|5|8|df=y}}
|birth_place       = [[Warsaw]], [[Congress Poland]], [[Russian Empire]]
|death_date        = {{death date and age|1982|1|24|1905|5|8|df=y}}
|death_place       = [[Warsaw]], [[People's Republic of Poland|Poland]]
|residence         = 
|citizenship       = 
|nationality       = Polish
|ethnicity         = 
|fields            = [[Mathematics]]
|workplaces        = 
|alma_mater        = [[Warsaw University]]
|doctoral_advisor  = [[Stefan Mazurkiewicz]]
|academic_advisors = 
|doctoral_students = 
|notable_students  = {{plainlist|1=
*[[Samuel Eilenberg]]
*[[Jan Jaworowski]]
*[[Krystyna Kuperberg]]
*[[Włodzimierz Kuperberg]]
*[[Andrzej Trybulec]]
*[[Krzysztof Edward Haman]]
}}
|known_for         = [[Borsuk's conjecture]]<br>[[Borsuk–Ulam theorem]]<br>[[Bing–Borsuk conjecture]]<br/>[[Retraction (topology)#Absolute neighborhood retract (ANR)|Absolute retract]]<br/>[[Retraction (topology)#Absolute neighborhood retract (ANR)|Absolute neighborhood retract]]<br/>[[Shape theory (mathematics)|Shape theory]]
|author_abbrev_bot = 
|author_abbrev_zoo = 
|influences        = 
|influenced        = 
|awards            = 
|religion          =
|signature         =  <!--(filename only)-->
|footnotes         = 
}}

'''Karol Borsuk''' (8 May 1905 – 24 January 1982) was a Polish [[mathematician]]. His main area of interest was [[topology]]. He made significant contributions to [[Shape theory (mathematics)|shape theory]], a term which he coined. He also  obtained important results in [[functional analysis]]. He was a professor of mathematics at the [[University of Warsaw]], a member of the [[Polish Academy of Sciences]], the [[Polish Mathematical Society]] and a leading representative of the [[Warsaw School (mathematics)|Warsaw School of Mathematics]].

==Life and career==
===Early life and education===
Borsuk was born in 1905 in [[Warsaw]] to father Marian, a surgeon, and mother Zofia (née Maciejewska). In 1923, he graduated from the [[Stanisław Staszic]] State Gymnasium in Warsaw.<ref>{{Cite web |url=https://liceumgottwalda.pl.tl/Znani-absolwenci-szko%26%23322%3By.htm |language=pl |title=Znani absolwenci szkoły |access-date=16 November 2024}}</ref> Between 1923–1927, he studied mathematics at the Faculty of Philosophy of the [[University of Warsaw]].

He received his [[master's degree]] and [[doctorate]] from Warsaw University in 1927 and 1930, respectively. His [[PhD]] thesis title was ''On the Subject of Topological Characterization of Euclidean Spheres'' and his advisor was [[Stefan Mazurkiewicz]]. From 1929 to 1934, he worked at the Faculty of Mathematics at the University of Warsaw. He became a professor in 1938. In the interwar period, Borsuk visited [[Lwów]], which was a thriving center of mathematics of the [[Second Polish Republic]], and began his collaboration with [[Stanisław Ulam]], especially in the field of topology. Borsuk joined the mathematicians in the [[Scottish Café]] and contributed to the open problems which they wrote down in the [[Scottish Book|famous book]].<ref name="Andrews"></ref>

===World War II===
During [[World War II]], he ran a stationery store and provided a secret meeting place for the [[Home Army]]. He designed and published a number of [[board games]] including ''[[Animal Husbandry (game)|Animal Husbandry]]'', which enjoyed great popularity and was re-released in 1997 as ''Superfarmer''.<ref>{{Cite web |url=https://wyborcza.pl/AkcjeSpecjalne/7,160474,24616437,topologia-polska-specjalnosc.html |language=pl |title=Borsuk przy telefonie i UFO z piątego wymiaru. Topologia - polska specjalność |website=wyborcza.pl |author=Marcin Bójko |date=5 April 2019 |access-date=16 November 2024}}</ref> In the years 1939–1944, he gave [[Education in Poland during World War II|secret lectures at the University of Warsaw]]. In 1943, he was arrested for his participation in the resistance movement and spent a couple of months at the [[Pawiak|Pawiak Prison]].<ref>{{cite book |last=Wanat |first=Leon |date=1985 |title=Za murami Pawiaka |trans-title=Behiand the Walls of Pawiak |url= |language=pl |location=Warsaw |publisher=Książka i Wiedza |page=346 |isbn=}}</ref> During the [[Warsaw Uprising]] in 1944, he was transported alongside his family to the [[Dulag 121 camp in Pruszków|Dulag 121 Camp]] in [[Pruszków]]. He managed to escape from the camp and remained in hiding until the end of the war.<ref name="Wójcik">{{Cite web |url=https://gigancinauki.pl/gn/biogramy/83897,Borsuk-Karol.html |language=pl |title=Biogramy |website=gigancinauki.pl |author=Wiesław Wójcik |access-date=16 November 2024}}</ref>

===Later career===
In 1945, he completed a project in collaboration with [[Bronisław Knaster]] and [[Kazimierz Kuratowski]] concerning the establishment of the [[Institute of Mathematics of the Polish Academy of Sciences]].<ref>{{Cite web |url=https://www.impan.pl/en/insitute/about-us/history |title=History |website=impan.pl |access-date=7 December 2024}}</ref> In 1946, he returned to the University of Warsaw where he served as the Head of the Institute of Mathematics from 1952 to 1964. In 1952, he became a member of the [[Polish Academy of Sciences]], and in 1953, a corresponding member of the [[Bulgarian Academy of Sciences]]. He was also a member of the [[Polish Mathematical Society]]. He worked as an editor-in-chief of ''Dissertationes Mathematicae'' and deputy editor-in-chief of ''[[Fundamenta Mathematicae]]''. In 1946–47, he lectured at the Institute for Advanced Study at [[Princeton University]], in 1959–60 at the [[University of California at Berkeley]], in 1963–64 at the [[University of Wisconsin at Madison]], and in 1967–68 at [[Rutgers University–New Brunswick]].<ref name="Wójcik"></ref> In 1954, he received the [[Officer]]'s Cross of the [[Order of Polonia Restituta]] for his "outstanding contributions to science".<ref>{{Cite web |url=https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=WMP1954112156 |language=pl |title=M.P. 1954 nr 112 poz. 1566 |website=isap.sejm.gov.pl |access-date=16 November 2024}}</ref> In 1976, he was awarded an [[honorary doctorate]] by the [[University of Zagreb]].<ref>{{Cite web |url=https://www.unizg.hr/fileadmin/rektorat/Istrazivanja/Poslijediplomski/Doktorski_programi/pocasni_doktori/knjizica_pocasnih_doktora/Borsuk_Ellenberg_Lefebvre_Bakaric.pdf |title=Karol Borsuk |website=unizg.hr |access-date=16 November 2024}}</ref>

Borsuk's students include: [[Samuel Eilenberg]], Andrzej Kirkor, [[Jan Jaworowski]], Andrzej Granas, Antoni Kosiński, Karol Sieklucki, Włodzimierz Holsztyński, Rafał Molski, Hanna Patkowska, Andrzej Jankowski, [[Włodzimierz Kuperberg]], Stanisław Spież, [[Krystyna Kuperberg]], Jerzy Dydak, [[Andrzej Trybulec]], Marian Orłowski, Alfred Surzycki.<ref>{{MathGenealogy|12548}}</ref>

==Research==
[[File:BorsukVermutungSimplizes.PNG|thumb|The illustration of the [[Borsuk conjecture]] in low dimensions]]
Borsuk introduced the theory of [[absolute retract]]s (ARs) and [[absolute neighborhood retract]]s (ANRs), and the [[cohomotopy group]]s, later called Borsuk–[[Edwin Spanier|Spanier]] cohomotopy groups. He also founded [[Shape theory (mathematics)|shape theory]]. He has constructed various beautiful examples of [[topological space]]s, e.g. an acyclic, 3-dimensional [[continuum (topology)|continuum]] which admits a fixed point free [[homeomorphism]] onto itself; also 2-dimensional, contractible polyhedra which have no free edge. 

His topological and geometric conjectures and themes stimulated research for more than half a century; in particular, his open problems stimulated the infinite-dimensional topology. Some of the notable mathematical concepts that bear Borsuk's name include [[Borsuk's conjecture]], [[Borsuk–Ulam theorem]] and [[Bing–Borsuk conjecture]].

==Private life==
In 1936, he married Zofia Paczkowska.<ref name="Andrews">{{Cite web |url=https://mathshistory.st-andrews.ac.uk/Biographies/Borsuk/ |title=Karol Borsuk |website=mathshistory.st-andrews.ac.uk |access-date=16 November 2024}}</ref> One of his two daughters, Magdalena, who was a Professor of Paleontology, was married to Polish mathematician [[Andrzej Białynicki-Birula]].<ref>{{Cite web |url=http://www.forumakad.pl/archiwum/98/7-8/artykuly/33-rody_uczone.htm |language=pl |title=Kresy, góry, Warszawa |website=forumakad.pl |author=Magdalena Bajer |access-date=16 November 2024 |archive-date=4 March 2016 |archive-url=https://web.archive.org/web/20160304201752/http://www.forumakad.pl/archiwum/98/7-8/artykuly/33-rody_uczone.htm |url-status=dead }}</ref> He died in Warsaw in 1982 and was buried at the [[Powązki Cemetery]].<ref>{{Cite web |url=https://cmentarze.um.warszawa.pl/pomnik.aspx?pom_id=13565 |language=pl |title=Warszawskie Zabytkowe Pomniki Nagrobne |website=cmentarze.um.warszawa.pl |access-date=16 November 2024}}</ref> In 2008, a commemorative plaque in honour of Borsuk was unveiled at the entrance to the tenement house in Warsaw at Filtrowa 63 Street where the mathematician used to live.<ref>{{Cite web |url=https://www.ptm.org.pl/zawartosc/odsloniecie-tablicy-upamietniajacej-prof-karola-borsuka |language=pl |title=Odsłonięcie tablicy upamiętniającej prof. Karola Borsuka |website=ptm.org.pl |date=28 October 2008 |access-date=16 November 2024}}</ref>

==Works==
* ''Geometria analityczna w n wymiarach'' (1950) (translated to English as ''Multidimensional Analytic Geometry'', [[Polish Scientific Publishers]], 1969)
* ''Podstawy geometrii'' (1955)
* ''Foundations of Geometry'' (1960) with [[Wanda Szmielew]], North Holland publisher<ref>{{cite journal|author=Freudenthal, H.|authorlink=Hans Freudenthal|title=Review: ''Foundations of geometry, Euclidean and Bolyai–Lobachevskian geometry, projective geometry''. By K. Borsuk and Wanda Szmielew. Revised English translation.|journal=Bull. Amer. Math. Soc.|year=1961|volume=67|issue=4|pages=342–344|url=https://www.ams.org/journals/bull/1961-67-04/S0002-9904-1961-10606-X/S0002-9904-1961-10606-X.pdf|doi=10.1090/s0002-9904-1961-10606-x|doi-access=free}}</ref>
* ''Theory of Retracts'' (1967), PWN, Warszawa.
* ''Theory of Shape'' (1975)
* ''Collected papers'' vol. I, (1983), PWN, Warszawa.

==See also==
* [[Zygmunt Janiszewski]]
* [[Stanislaw Ulam]]
* [[Scottish Café]]
* [[Ham sandwich theorem]]

==References==
{{reflist}}

== External links ==
{{commons category|Karol Borsuk (mathematician)}}
*{{MacTutor Biography|id=Borsuk}}
*{{MathGenealogy |id=12548}}

{{Authority control}}

{{DEFAULTSORT:Borsuk, Karol}}
[[Category:Warsaw School of Mathematics]]
[[Category:Topologists]]
[[Category:Members of the Polish Academy of Sciences]]
[[Category:University of Warsaw alumni]]
[[Category:Academic staff of the University of Warsaw]]
[[Category:People from Warsaw Governorate]]
[[Category:1905 births]]
[[Category:1982 deaths]]
[[Category:Prisoners of Dulag 121 Pruszków]]
[[Category:Recipients of the Medal of the 10th Anniversary of the People's Republic of Poland]]