Christian Sophus Juel (25 January 1855, Randers – 24 January 1935,

Copenhagen Copenhagen ( or .; da, København ) is the capital and most populous city of Denmark, with a proper population of around 815.000 in the last quarter of 2022; and some 1.370,000 in the urban area; and the wider Copenhagen metropolitan ar ...

) was a Danish mathematician, specializing in geometry.

Education and career

Juel went to school in Svendborg and from 1871 studied at the

Technical University of Denmark The Technical University of Denmark ( da, Danmarks Tekniske Universitet), often simply referred to as DTU, is a polytechnic university and school of engineering. It was founded in 1829 at the initiative of Hans Christian Ørsted as Denmark's fi ...

. From 1876 he studied mathematics at the

University of Copenhagen The University of Copenhagen ( da, Københavns Universitet, KU) is a prestigious public university, public research university in Copenhagen, Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in ...

; there he received In 1879 his undergraduate degree in mathematics and in 1885 his Ph.D. (promotion) with thesis ''Inledning i de imaginaer linies og den imaginaer plans geometrie''. From 1894 he was a docent at the Technical University of Denmark, where he became in 1897 a full professor; during this time he also sometimes lectured at the University of Copenhagen. Juel did research on projective geometry, algebraic curves, polyhedra, and surfaces of revolution from ovals. In projective geometry, he generalized results of Karl von Staudt and independently obtained results similar to those of Corrado Segre. In addition to a monograph on projective geometry, Juel wrote textbooks dealing with stereometry, rational mechanics, and introductory mathematics for chemists. From 1889 to 1915 he was an editor of ''Matematisk Tidsskrift''. In 1922 he was made a member of the Finnish Academy of Sciences. In 1925 he was made a member of the Norwegian Academy of Sciences and an honorary member of the Danish Mathematical Association. In 1928 he was an

invited speaker at the International Congress of Mathematicians This is a list of International Congresses of Mathematicians Plenary and Invited Speakers. Being invited to talk at an International Congress of Mathematicians has been called "the equivalent, in this community, of an induction to a hall of fame." ...

at Bologna and gave a talk ''Beispiele von Elementarkurven und Elementarflächen''. His wife's father was the mathematician and astronomer

Thorvald Nicolai Thiele Thorvald Nicolai Thiele (24 December 1838 – 26 September 1910) was a Danish astronomer and director of the Copenhagen Observatory. He was also an actuary and mathematician, most notable for his work in statistics, interpolation and the three ...

. Juel was awarded in 1913 a rank of Knight (''Ridder'') in 1913 and in 1921 a rank of the Cross of Honour (''Dannebrogordenens hæderstegn'') of the Order of Dannebrog.

Selected works

*''Vorlesungen über Projektive Geometrie mit besonderer Berücksichtigung der von Staudtschen Imaginärtheorie'', Grundlehren der mathematischen Wissenschaften, Springer Verlag 1934
Online
*''Vorlesungen über Mathematik für Chemiker'', Kopenhagen 1890 *''Elementar stereometri'', Kopenhagen, 1896 *''Analytisk stereometri'', Kopenhagen, 1897 *''Ren og anvendt aritmetik'', Kopenhagen 1902; 153 pages
''Forlaesinger over rationel mekanik''
Kopenhagen 1913, 2nd edition 1920
''Grundgebilde der projectiven Geometrie''
Acta Mathematica, vol. 14, 1890, 1–30 *''Über die Parameterbestimmung von Punkten auf Curven zweiter und dritter Ordnung. Eine geometrische Einleitung in die Theorie der logarithmischen und elliptischen Functionen'', Mathematische Annalen, vol. 47, 1896, 72-10
Online
*

Sources

*Herbert Oettel in Dictionary of Scientific Biography

References

{{DEFAULTSORT:Juel, Christian 1855 births 1935 deaths 19th-century Danish mathematicians 20th-century Danish mathematicians People from Randers University of Copenhagen alumni Academic staff of the Technical University of Denmark Danish knights