Charles Ehresmann (19 April 1905 – 22 September 1979) was a French mathematician who worked on differential topology and category theory. He is known for work on the topology of Lie groups, the jet concept (see jet bundle), and his seminar on category theory.
He attended the École Normale Supérieure in Paris before performing one year of military service. He finished his PhD thesis Sur la topologie de certains espaces homogènes (French: On the topology of certain homogeneous spaces) in 1934 under the supervision of Élie Cartan.
In 1957 he founded the mathematical journal Cahiers de Topologie et Géometrie Différentielle Categoriques.
Jean Dieudonné 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, Wu Wen-Tsün, André Haefliger, Valentin Poénaru, Daniel Tanré. His very first student was Jacques Feldbau.
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