Johannes Trolle Hjelmslev (; 7 April 1873 – 16 February 1950) was a mathematician from
Hørning :''not to be confused with the village of Hørning in Randers municipality''
Hørning is a town in central Denmark with a population of 8,395 (1 January 2022), ,
Denmark
)
, song = ( en, "King Christian stood by the lofty mast")
, song_type = National and royal anthem
, image_map = EU-Denmark.svg
, map_caption =
, subdivision_type = Sovereign state
, subdivision_name = Kingdom of Denmark
, establishe ...
. Hjelmslev worked in
geometry
Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is c ...
and
history of geometry
Geometry (from the grc, γεωμετρία; ''geo-'' "earth", '' -metron'' "measurement") arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the stud ...
. He was the discoverer and eponym of the
Hjelmslev transformation, a method for
mapping an entire
hyperbolic plane
In mathematics, hyperbolic geometry (also called Lobachevskian geometry or Bolyai–Lobachevskian geometry) is a non-Euclidean geometry. The parallel postulate of Euclidean geometry is replaced with:
:For any given line ''R'' and point ''P'' ...
into a
circle
A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. Equivalently, it is the curve traced out by a point that moves in a plane so that its distance from a given point is const ...
with a finite
radius
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
.
He was the father of
Louis Hjelmslev
Louis Trolle Hjelmslev (; 3 October 189930 May 1965) was a Danish linguist whose ideas formed the basis of the Copenhagen School of linguistics. Born into an academic family (his father was the mathematician Johannes Hjelmslev), Hjelmslev studie ...
.
Originally named Johannes Trolle Petersen, he changed his patronymic to the surname Hjelmslev to avoid confusion with
Julius Petersen
Julius Peter Christian Petersen (16 June 1839, Sorø, West Zealand – 5 August 1910, Copenhagen) was a Danish mathematician. His contributions to the field of mathematics led to the birth of graph theory.
Biography
Petersen's interes ...
. Some of his results are known under his original name, including the
Petersen–Morley theorem.
Publications
*Johannes Hjelmslev, ''Grundprinciper for den infinitesimale Descriptivgeometri med Anvendelse paa Læren om variable Figurer. Afhandling for den philosophiske Doctorgrad'', 1897
*Johannes Hjelmslev, ''Deskriptivgeometri: Grundlag for Forelæsninger paa Polyteknisk Læreanstalt'', Jul. Gjellerup 1904
*Johannes Hjelmslev
''Geometriske Eksperimenter'' Jul. Gjellerup 1913
*Johannes Hjelmslev
''Darstellende Geometrie'', Teubner 1914*Johannes Hjelmslev, ''Geometrische Experimente'', Teubner 1915
*Johannes Hjelmslev, ''Lærebog i Geometri til Brug ved den Polytekniske Læreanstalt'', Jul. Gjellerup 1918
*Johannes Hjelmslev
''Die natürliche Geometrie- vier Vorträge'', Hamburger Mathematische Einzelschriften 1923*Johannes Hjelmslev, Om et af den danske matematiker Georg Mohr udgivet skrift ''Euclides Danicus', udkommet i Amsterdam i 1672", ''Matematisk Tidsskrift'' B, 1928, pp 1-7
*Johannes Hjelmslev, Grundlagen der projektiven Geometrie, 1929
*Johannes Hjelmslev, Beiträge zur Lebensbeschreibung von Georg Mohr, Det Kongelige Danske Videnskabernes Selskab, Math.-Fys. Meddelelser, Bd.11, 1931, Nr.4
*Johannes Hjelmslev, ''Grundlag for den projektive Geometri'', Gyldendal 1943
See also
*
Hjelmslev's theorem
References
*
*Gottwald, Ilgauds, Schlote ''Lexikon bedeutender Mathematiker'', Leipzig 1990
External links
*''Salmonsens Konversationsleksikon''
*''Salmonsens Konversationsleksikon''
{{DEFAULTSORT:Hjelmslev, Johannes Trolle
1873 births
1950 deaths
20th-century Danish mathematicians
Geometers
People from Skanderborg Municipality
University of Copenhagen faculty
Rectors of the University of Copenhagen
Members of the Royal Society of Sciences in Uppsala