Spezielle Algebren und transitive Operationen.
Spherical roots of spherical varieties
Brion proved that the valuation cone of a complex spherical variety is a fundamental domain for a finite reflection group, called the little Weyl group. The principal goal of this paper is to generalize this theorem to fields of characteristic unequal to 2. We also prove a weaker version which holds in characteristic 2, as well. Our main tool is a generalization of Akhiezer’s classification of spherical varieties of rank 1.
Spin groups over a commutative ring and the associated root data (odd rank case).
Stability and equivariant maps.
Stability of meromorphic vector fields in projective spaces.
Stability of pencils of plane quartic curves
In questa nota si danno dei criteri per la stabilità di fasci di quartiche piane.
Stability of Two-Dimensional Local Rings. I.
Stabilizers for nondegenerate matrices of boundary format and Steiner bundles.
In this paper nondegenerate multidimensional matrices of boundary format in V0 ⊗ ... ⊗ Vp are investigated by their link with Steiner vector bundles on product of projective spaces. For any nondegenerate matrix A the stabilizer for the SL(V0) x ... x SL(Vp)-action, Stab(A), is completely described. In particular we prove that there exists an explicit action of SL(2) on V0 ⊗ ... ⊗ Vp such that Stab(A)0 ⊆ SL(2) and the equality holds if and only if A belongs to a unique SL(V0) x ... x SL(Vp)-orbit...
Stable affine models for algebraic group actions.
Stable rationality of certain PGLn-quotients.
Stable Vector Bundles of Rank 2 on IP3.
Stably rational algebraic tori
The rationality of a stably rational torus with a cyclic splitting field is proved.
Stratification of the discriminant in Reflection groups.
Stratifikation von Quotientenmannigfaltigkeiten (in Charakteristik 0) und insbesondere der Modulmannigfaltigkeiten für Kurven.
Structure du groupe de Grothendieck équivariant d’une courbe et modules galoisiens
Cet article est consacré à l’étude de la structure d’anneau du groupe de Grothendieck équivariant d’une courbe projective munie d’une action d’un groupe fini. On explicite cette structure en introduisant un groupe de classes de cycles à coefficients dans les caractères et une notion d’auto-intersection pour ces cycles. De ce résultat, on déduit une expression de la caractéristique d’Euler équivariante d’un -faisceau.
Structure of birational automorphism groups, I: non-uniruled varieties.
Structures galoisiennes et courbes elliptiques
Subspaces of moduli spaces of rank one local systems
Subvarieties of Moduli Spaces.
Sui sistemi di bifattori in caratteristica positiva