## Archives Henry Poincaré

Between 1880 and 1930 mathematical and theoretical physics underwent substantial changes. on the one hand linked to the emergence of several fields of mathematics (group theory, algebraic geometry, topology) and on the other hand the disintegration of the Newtonian physics under the effect of the discovery of the electromagnetic waves, the X-rays, the radioactivity, the electrons, and the quantum energy. It is specific to the French scientist Henri Poincaré (1854-1912) to have participated in all these transformations. At the age of 26, Poincaré discovered the theory of Fuchsian functions, thanks to which one could resolve any linear differential equation with algebraic coefficients. The impact of this discovery was to make him corresponding member of the German Academies, even before being nominated for a chair of mathematical physics at the Faculty of Sciences and elected as member of the Institute. Throughout these positions, Poincaré influenced French mathematical research for more than 25 years while pursuing his teaching and research activities. At his death in 1912, he had published some 600 articles on pure mathematics, geometry, celestial mechanics, physics, and philosophy of science.