Ingebrigt Johansson

Ingebrigt Johansson (1904–1987)

Ingebrigt Johansson (born October 24, 1904 in Narvik , † April 24, 1987 in Oslo ) was a Norwegian mathematician , logician and university professor .

Life and career

Johansson studied mathematics at the University of Oslo from 1923–1928 . He then went on to further studies in Bonn and Frankfurt am Main . In 1931 he received his doctorate as Dr. phil. and in the same year became a research assistant at the University of Oslo, where he was then appointed professor in 1942 .

Ingebrigt Johansson was President of the Norwegian Mathematical Society between 1935 and 1946 . From 1937 on he was a member of the Norwegian Academy of Sciences .

Scientific achievements

Johansson's scientific research spanned several areas of mathematics , but mainly concerned the areas of geometry , topology and mathematical logic :

In geometry, Johansson gave a geometric interpretation of the quaternions and investigated the Laguerre geometry .
In topology he worked on Dehn's lemma .
In his dissertation he proved that the fundamental group of a non-compact surface must always be a free group . An application of this result is a topological proof of the Nielsen-Schreier theorem that subsets of free groups are always free groups.

Particularly noteworthy are his achievements in the field of intuitionistic logic . Here he is considered the founder of the so-called minimal calculus .

literature

Siegfried Gottwald , Hans-Joachim Ilgauds and Karl-Heinz Schlote (ed.): Lexicon of important mathematicians . Verlag Harri Deutsch, Thun 1990, ISBN 3-8171-1164-9 , p. 234 .

Web links

Selection of Johansson's work in MathSciNet
Literature by and about Ingebrigt Johansson in the bibliographic database WorldCat

References and footnotes

^ Johansson, A representation of the two-row matrices (and the quaternions) by straight lines of space, In: Acta Mathematica , Volume 59, 1932, pp. 443–453.
^ Johansson, A contribution to the planar geometry by Laguerre, In: Mathematische Zeitschrift , Volume 32, 1930, pp. 259-290 ( digitized version ).
^ I. Johansson, On singular elementary surfaces and the Dehn's lemma , In: Mathematische Annalen , Volume 110, 1935, pp. 312-330 ( digitized version ); Part 2, thematic annals , Volume 115, 1938, pp. 658-669 ( digitized version ).
↑ Johansson, The Minimal Calculus, a reduced intuitionist formalism, In: Compositio Mathematica , Volume 4, 1936, pp. 119-136.

personal data
SURNAME	Johansson, Ingebrigt
BRIEF DESCRIPTION	Norwegian mathematician
DATE OF BIRTH	October 24, 1904
PLACE OF BIRTH	Narvik
DATE OF DEATH	April 24, 1987
Place of death	Oslo

[1] Johansson, A representation of the two-row matrices (and the quaternions) by straight lines of space, In: Acta Mathematica , Volume 59, 1932, pp. 443–453.

[2] Johansson, A contribution to the planar geometry by Laguerre, In: Mathematische Zeitschrift , Volume 32, 1930, pp. 259-290 ( digitized version ).

[3] I. Johansson, On singular elementary surfaces and the Dehn's lemma , In: Mathematische Annalen , Volume 110, 1935, pp. 312-330 ( digitized version ); Part 2, thematic annals , Volume 115, 1938, pp. 658-669 ( digitized version ).

[4] Johansson, The Minimal Calculus, a reduced intuitionist formalism, In: Compositio Mathematica , Volume 4, 1936, pp. 119-136.