1. Equivalence motivique des groupes algebriques semisimples
- Author
-
De Clercq, Charles
- Subjects
Mathematics - Algebraic Geometry - Abstract
Two semisimple algebraic groups are said to be motivic equivalent if the motives of the associated twisted flag varieties are isomorphic modulo any prime p. The purpose of this note is to construct the combinatorial invariants which characterize motivic equivalence and which are the motivic analogues of the Tits indices which appear in the classification of semisimple algebraic groups. The expression of these invariants -the Tits p-indexes- in terms of the classical invariants associated to the natural underlying structures of semisimple algebraic groups allow to produce algebraic criteria of motivic equivalence, generalizing Vishik's criterion of motivic equivalence for the motives of quadrics. It also clarifies the relation between the motives and the rational geometry of twisted flag varieties. Deux groupes semisimples sont dits motiviquement equivalents si les motifs des varietes de drapeaux generalisees associees sont isomorphes modulo tout nombre premier p. L'objet de cette note est de construire les invariants combinatoires qui caracterisent l'equivalence motivique et sont les analogues motiviques des indices de Tits apparaissant dans la classification des groupes algebriques semisimples. L'expression de ces invariants -les p-indices de Tits superieurs- en fonction des indices classiques associes aux structures naturelles sous-jacentes aux groupes semisimples permet de produire des criteres algebriques d'equivalence motivique, generalisant le critere de Vishik d'equivalence motivique des quadriques. Elle permet en outre de clarifier le lien qu'entretiennent les motifs et la geometrie birationnelle des varietes de drapeaux., Comment: in French. The article refers several times to the determination of the Tits p-indexes of absolutely simple groups, which is contained in the article "On the Tits p-indexes of semisimple algebraic groups" (joint with Skip Garibaldi). A draft of this article (whose motivic part is not yet filled) is available on http://www.math.univ-paris13.fr/~declercq/ as well as an abridged english version of the article
- Published
- 2015