Charles Ehresmann

Charles Ehresmann, born in Strasbourg on 19 April 1905 when Alsace was under German rule and died at Amiens on 22 September 1979, was a French mathematician who worked in differential topology and category theory. Born into a poor Alsatian family, he was taught first in German and then in French, entered the École Normale Supérieure in Paris in 1924, studied at Göttingen and Princeton, and received his doctorate from Paris in 1934 for work on the topology of differential manifolds and homogeneous spaces. He taught at Strasbourg, whose faculties spent the war at Clermont-Ferrand, and from 1955 held a chair of topology created for him at the University of Paris until he retired in 1975. He was one of the creators of differential topology, making major contributions from 1941 to the modern view of fibre spaces, manifolds, foliations and jets. From 1957 he became a leader in category theory, working on local categories, structures defined by atlases and germs of categories, and he founded a journal for the field.