High Quality Content by WIKIPEDIA articles! Pierre René, Viscount Deligne (born 3 October 1944 in Brussels) is a Belgian mathematician. He is known for work on the Weil conjectures, leading finally to a complete proof in 1973.He was born in Brussels, and studied at the Universite Libre de Bruxelles (ULB).After completing a doctorate under the supervision of Alexander Grothendieck, he worked with him at the Institut des Hautes Études Scientifiques (IHÉS) near Paris, initially on the generalization within scheme theory of Zariski's main theorem. In 1968, he also worked with Jean-Pierre Serre; their work led to important results on the l-adic representations attached to modular forms, and the conjectural functional equations of L-functions. Deligne's also focused on topics in Hodge theory. He introduced weights and tested them on objects in complex geometry. He also collaborated with David Mumford on a new description of the moduli spaces for curves. Their work came be seen as an introduction to one form of the theory of algebraic stacks, and recently has been applied to questions arising from string theory.