Some observations on motivic cohomolgy of arithmetic schemes.
Stacks and the homotopy theory of simplicial sheaves.
Stacks of group representations
We start with a small paradigm shift about group representations, namely the observation that restriction to a subgroup can be understood as an extension-of-scalars. We deduce that, given a group , the derived and the stable categories of representations of a subgroup can be constructed out of the corresponding category for by a purely triangulated-categorical construction, analogous to étale extension in algebraic geometry. In the case of finite groups, we then use descent methods to investigate...
Sur l’indépendance de en cohomologie -adique sur les corps locaux
Gabber a déduit son théorème d’indépendance de de la cohomologie d’intersection d’un résultat général de stabilité sur les corps finis. Dans cet article, nous démontrons un analogue sur les corps locaux de ce résultat général. Plus précisément, nous introduisons une notion d’indépendance de pour les systèmes de complexes de faisceaux -adiques sur les schémas de type fini sur un corps local équivariants sous des groupes finis et nous établissons sa stabilité par les six opérations de Grothendieck...
Tame stacks in positive characteristic
We introduce and study a class of algebraic stacks with finite inertia in positive and mixed characteristic, which we call tame algebraic stacks. They include tame Deligne-Mumford stacks, and are arguably better behaved than general Deligne-Mumford stacks. We also give a complete characterization of finite flat linearly reductive schemes over an arbitrary base. Our main result is that tame algebraic stacks are étale locally quotient by actions of linearly reductive finite group schemes.
Tensor products of drinfeld modules and v-adic representations.
The Lefschetz trace formula for algebraic stacks.
The one-motif of an algebraic surface
The sign of the functional equation of the L-function of an orthogonal motive.
The six operations for sheaves on Artin stacks I: Finite coefficients
In this paper we develop a theory of Grothendieck’s six operations of lisse-étale constructible sheaves on Artin stacks locally of finite type over certain excellent schemes of finite Krull dimension. We also give generalizations of the classical base change theorems and Kunneth formula to stacks, and prove new results about cohomological descent for unbounded complexes.
The six operations for sheaves on Artin stacks II: Adic coefficients
The stack quotient of a groupoid
The structure of a local embedding and Chern classes of weighted blow-ups
For a proper local embedding between two Deligne-Mumford stacks and , we find, under certain mild conditions, a new (possibly non-separated) Deligne-Mumford stack , with an etale, surjective and universally closed map to the target , and whose fiber product with the image of the local embedding is a finite union of stacks with corresponding etale, surjective and universally closed maps to . Moreover, a natural set of weights on the substacks of allows the construction of a universally closed...
Théorème de Van Kampen pour les champs algébriques
Théorèmes d'existence pour les modifications analytiques.
Théorie différentielle du contact maximal en inégale caractéristique
Torseurs pour les motifs et pour les representations p-adiques potentiellement de type CM.
Un teorema sulle trasformazioni monoidali di spazi algebrici
Valeurs spéciales des fonctions des motifs
Versal Deformations and Algebraic Stacks.