Charles Ehresmann was a French

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 mathematician

Mathematician

A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....

 who worked on differential topology

Differential topology

In mathematics, differential topology is the field dealing with differentiable functions on differentiable manifolds. It is closely related to differential geometry and together they make up the geometric theory of differentiable manifolds.- Description :...

 and category theory

Category theory

Category theory is an area of study in mathematics that examines in an abstract way the properties of particular mathematical concepts, by formalising them as collections of objects and arrows , where these collections satisfy certain basic conditions...

. He is known for work on the topology of Lie group

Lie group

In mathematics, a Lie group is a group which is also a differentiable manifold, with the property that the group operations are compatible with the smooth structure...

s, the jet concept (see jet bundle

Jet bundle

In differential geometry, the jet bundle is a certain construction which makes a new smooth fiber bundle out of a given smooth fiber bundle. It makes it possible to write differential equations on sections of a fiber bundle in an invariant form...

), and his seminar on category theory.

He attended the École Normale Supérieure

École Normale Supérieure

The École normale supérieure is one of the most prestigious French grandes écoles...

 in Paris

Paris

Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

 before performing one year of military service. He finished his PhD thesis Sur la topologie de certains espaces homogènes (French

French language

French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

: On the topology of certain homogeneous space

Homogeneous space

In mathematics, particularly in the theories of Lie groups, algebraic groups and topological groups, a homogeneous space for a group G is a non-empty manifold or topological space X on which G acts continuously by symmetry in a transitive way. A special case of this is when the topological group,...

s) in 1934 under the supervision of Élie Cartan

Élie Cartan

Élie Joseph Cartan was an influential French mathematician, who did fundamental work in the theory of Lie groups and their geometric applications...

.

In 1957 he founded the mathematical journal Cahiers de Topologie et Géometrie Différentielle Categoriques

Cahiers de Topologie et Géometrie Différentielle Categoriques

The Cahiers de Topologie et Géométrie Différentielle Catégoriques is a French mathematical scientific journal established by Charles Ehresmann in 1957. It was originally published under the name Cahiers de Topologie and later Cahiers de Topologie et Géométrie Différentielle...

.

Jean Dieudonné

Jean Dieudonné

Jean Alexandre Eugène Dieudonné was a French mathematician, notable for research in abstract algebra and functional analysis, for close involvement with the Nicolas Bourbaki pseudonymous group and the Éléments de géométrie algébrique project of Alexander Grothendieck, and as a historian of...

 describes 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 ... "

He had 76 Ph.D. students, including Georges Reeb

Georges Reeb

Georges Henri Reeb was a French mathematician. He worked in differential topology, differential geometry, differential equations, topological dynamical systems theory and non-standard analysis....

, Wu Wen-Tsün

Wu Wenjun

Wu Wenjun is a Chinese mathematician and academician at the Chinese Academy of Sciences .-Biography:Wu's ancestral hometown is Jiashan, in Jiaxing of Zhejiang. Wu was born in Shanghai, China where he would later graduate from Chiao Tung University in 1940...

, André Haefliger

André Haefliger

André Haefliger is a Swiss mathematician who works primarily on topology.He studied mathematics in Lausanne. He received his PhD in 1958 from the University of Strasbourg under the supervision of Charles Ehresmann with "Structures feuilletées et cohomologie à valeurs dans un faisceau de...

, Valentin Poénaru

Valentin Poénaru

Valentin Alexandre Poénaru is a Professor of Mathematics at Université de Paris-Sud. He specializes in low-dimensional topology.Born in Romania, he did his undergraduate studies at the University of Bucharest. In 1962, he was an invited speaker at the International Congress of Mathematicians in...

, Daniel Tanré.

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