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'''Horst Schubert''' (11 June 1919 in [[Chemnitz]]) is a German mathematician.

Schubert studied mathematics and physics at the Universities of Frankfurt am Main, Zürich and Heidelberg, where in 1948 he received his PhD under [[Herbert Seifert]] with thesis ''Die eindeutige Zerlegbarkeit eines Knotens in Primknoten''.<ref>[http://books.google.com/books/about/Die_Eindeutige_Zerlegbarkeit_Eines_Knote.html?id=ErRvQgAACAAJ ''Die eindeutige Zerlegbarkeit eines Knotens in Primknoten'', dissertation published 1 Jan. 1949]</ref><ref>{{MathGenealogy|id=21623}}</ref> From 1948 to 1956 Schubert was an assistant in Heidelberg, where he received in 1952 his [[habilitation]] qualification. From 1959 he was a ''professor extraordinarius'' and from 1962 a ''professor ordinarius'' at the [[University of Kiel]]. From 1969 he was a professor at the [[University of Düsseldorf]].

In 1949 he published his proof that every [[Knot theory|oriented knot]] in [[3-sphere|<math>S^3</math>]] decomposes as a [[Connected sum|connect-sum]] of [[prime knot]]s in a unique way, up to reordering.<ref>Schubert, H. Die eindeutige Zerlegbarkeit eines Knotens in Primknoten. S.-B Heidelberger Akad. Wiss. Math.-Nat. Kl. 1949 (1949), 57&ndash;104.</ref> After this proof  he found a new proof based on his study of incompressible tori in knot complements; he published this work ''Knoten und Vollringe'' in ''[[Acta Mathematica]]'', where he defined satellite and companion knots.<ref>Schubert, H. ''Knoten und Vollringe''. Acta Math. 90 (1953), 131&ndash;286.</ref> His doctoral students include Theodor Bröcker.

==Selected works==
* ''Kategorien''. 2 vols. Springer, 1970 (trans. into Eng. by Eva Gray: ''Categories''. Springer-Verlag, 1972 ISBN 0387057838)
* ''Topologie- Eine Einführung''. Teubner, 1969, 3rd edn. 1971 (trans. into Eng. by Siegfried Moran: ''Topology''. Macdonald & Co. 1968 ISBN 0356020770)
* [http://gdz.sub.uni-goettingen.de/dms/load/img/?PPN=GDZPPN002136198 ''Knoten'', Jahresbericht DMV, vol. 69, 1967/68, p. 184]

==See also==
* [[Satellite knot]]

==References==
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{{Persondata
| NAME              = Schubert, Horst
| ALTERNATIVE NAMES =
| SHORT DESCRIPTION = mathematician
| DATE OF BIRTH     = 11 June 1919
| PLACE OF BIRTH    =
| DATE OF DEATH     =
| PLACE OF DEATH    =
}}
{{DEFAULTSORT:Schubert, Horst}}
[[Category:20th-century mathematicians]]
[[Category:German mathematicians]]
[[Category:Topologists]]
[[Category:1919 births]]
[[Category:Living people]]