Lebesgue, Henri

Born June 28, 1875, in Beauvais, Oise Department; died July 26, 1941, in Paris. French mathematician. Member of the Paris Academy of Sciences (1922).

Lebesgue was appointed a professor at the University of Paris in 1910. He is one of the founders of the modern theory of functions of a real variable. His greatest contribution is the creation of the theory of measure and the concept of a measurable function, as well as the introduction of a new definition of the integral based on the theory of measure and permitting the integration of an extraordinarily wide class of functions. He applied his definition of the integral to Fourier series. His investigations of the possibility of the analytic representation of functions facilitated the creation of the descriptive theory of functions. Lebesgue also obtained important results in geometry and topology.