Navarro, Vicenç (Navarro Aznar)2019-04-262019-04-2619920214-1493https://hdl.handle.net/2445/132480In this paper, we emphasize Deligne's theory of weights, in order to prove that some stratifications of algebraic varieties are perfect. In particular, we study in some detail the Bialynicki-Birula's stratifications and the stratifications considered by F. Kirwan to compute the cohomology of symplectic or geometric quotients. Finally we also appoint the motivic formulation of this approach, which contains the Hodge theoretic forrnulation.19 p.application/pdfeng(c) Universitat Autònoma de Barcelona, 1992ÀlgebraGeometriaAlgebraGeometryinfo:eu-repo/semantics/article0726832019-04-26info:eu-repo/semantics/openAccess