He was an early member of the Bourbaki group, and is known for his work on the differential geometry of smooth fiber bundles, notably the introduction of the concepts of Ehresmann connection and of jet bundles, and for his seminar on category theory.
He completed his PhD thesis entitled Sur la topologie de certains espaces homogènes (On the topology of certain homogeneous spaces) at ENS in 1934 under the supervision of Élie Cartan.[3]
From 1955 he was Professor of Topology at Sorbonne, and after the reorganization of Parisian universities in 1969 he moved to Paris Diderot University (Paris 7).
After his retirement in 1975 and until 1978 he gave lectures at the University of Picardy at Amiens, where he moved because his second wife, Andrée Charles-Ehresmann, was a professor of mathematics there. He died at Amiens in 1979.[1][2]
In the first part of his career Ehresmann introduced many new mathematical objects in differential geometry and topology, which gave rise to entire new fields, often developed later by his students.[8][9][2]
His collected works, edited by his wife, appeared in seven volumes in 1980–1983 (four volumes published by Imprimerie Evrard, Amiens, and the rest in the journal Cahiers de Topologie et Géométrie Différentielle Catégoriques, which he had founded in 1957).[30] His publications include also the books Catégories et structures (Dunod, Paris, 1965) and Algèbre (1969).
Jean Dieudonné described Ehresmann's personality as "... distinguished by forthrightness, simplicity, and total absence of conceit or careerism. As a teacher he was outstanding, not so much for the brilliance of his lectures as for the inspiration and tireless guidance he generously gave to his research students ... "[2]
^Ehresmann, Charles (1949). "Sur la théorie des espaces fibres" [On the theory of fibred bundles]. Colloques Internat. Centre Nat. Rech. Sci. (Topologie Algebrique) (in French). 12: 3–15. Zbl0039.39703.
^Ehresmann, Charles (1955). "Les prolongements d'un espace fibré différentiable" [The prolongations of a differentiable fibred bundle]. Comptes rendus de l'Académie des Sciences (in French). 240: 1755–1757.
^Hopf, Heinz (1948). "Zur Topologie der komplexen Mannigfaltigkeiten" [On the topology of complex manifolds]. Studies and Essays Presented to R. Courant on His 60th Birthday (in German). New York: 167–185.
^Haefliger, André (2005). "Naissance des feuilletages, d'Ehresmann-Reeb à Novikov" [Birth of foliations, from Ehresmann-Reeb to Novikov]. Géométrie au XXe Siècle, 1930-2000: Histoire et Horizons (in French). Hermann: 257–272. CiteSeerX10.1.1.694.1226.
'The mathematical legacy of Charles Ehresmann', Proceedings of the 7th Conference on the Geometry and Topology of Manifolds: The Mathematical Legacy of Charles Ehresmann, Będlewo (Poland), 8.05.2005–15.05.2005, Edited by J. Kubarski, J. Pradines, T. Rybicki, R. Wolak, Banach Center Publications, vol. 76, Institute of Mathematics of the Polish Academy of Sciences, Warsaw, 2007. https://www.impan.pl/pl/wydawnictwa/banach-center-publications/all/76