2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/69823This is my Habilitation a Diriger des Recherches (French thing). In this paper I summarize the work I have done to realize the program of Witten called -non abelian localization-. This work deals first with problems of localization in equivariant cohomology. The second part of this paper concerns the Guillemin-Sternberg problem -Quantization commutes with reduction- in the geometric quantization procedure.35 pages, in FrenchDifferential GeometrySymplectic Geometrytext