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Henri Leon Lebesgue

Henri Lebesgue
Lebesgue 2.jpeg
Born (1875-06-28)June 28, 1875
Beauvais, Oise, France
Died July 26, 1941(1941-07-26) (aged 66)
Paris, France
Nationality French
Fields Mathematics
Institutions University of Rennes
University of Poitiers
University of Paris
Collège de France
Alma mater École Normale Supérieure
University of Paris
Doctoral advisor Émile Borel
Doctoral students Paul Montel
Zygmunt Janiszewski
Georges de Rham
Known for Lebesgue integration
Lebesgue measure
Notable awards Fellow of the Royal Society
Poncelet Prize for 1914

Henri Léon Lebesgue ForMemRS (French: [ɑ̃ʁi leɔ̃ ləbɛɡ]; June 28, 1875 – July 26, 1941) was a French mathematician most famous for his theory of integration, which was a generalization of the 17th century concept of integration—summing the area between an axis and the curve of a function defined for that axis. His theory was published originally in his dissertation Intégrale, longueur, aire ("Integral, length, area") at the University of Nancy during 1902.

Henri Lebesgue was born on 28 June 1875 in Beauvais, Oise. Lebesgue's father was a typesetter and his mother was a school teacher. His parents assembled at home a library that the young Henri was able to use. His father died of tuberculosis when Lebesgue was still very young and his mother had to support him by herself. As he showed a remarkable talent for mathematics in primary school, one of his instructors arranged for community support to continue his education at the Collège de Beauvais and then at Lycée Saint-Louis and Lycée Louis-le-Grand in Paris.

In 1894 Lebesgue was accepted at the École Normale Supérieure, where he continued to focus his energy on the study of mathematics, graduating in 1897. After graduation he remained at the École Normale Supérieure for two years, working in the library, where he became aware of the research on discontinuity done at that time by René-Louis Baire, a recent graduate of the school. At the same time he started his graduate studies at the Sorbonne, where he learned about Émile Borel's work on the incipient measure theory and Camille Jordan's work on the Jordan measure. In 1899 he moved to a teaching position at the Lycée Central in Nancy, while continuing work on his doctorate. In 1902 he earned his Ph.D. from the Sorbonne with the seminal thesis on "Integral, Length, Area", submitted with Borel, four years older, as advisor.


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