Singularities of Closures of K-orbits on Flag Manifolds.
Singularities of Quotients by Vector Fields in Characteristic p.
-equivariant polynomial automorphisms of the binary forms
We consider the space of binary forms of degree denoted by . We will show that every polynomial automorphism of which commutes with the linear -action and which maps the variety of forms with pairwise distinct zeroes into itself, is a multiple of the identity on .
SL2 actions and cohomology of Schubert varieties
Smallness problem for quantum affine algebras and quiver varieties
The geometric small property (Borho-MacPherson [2]) of projective morphisms implies a description of their singularities in terms of intersection homology. In this paper we solve the smallness problem raised by Nakajima [37, 35] for certain resolutions of quiver varieties [37] (analogs of the Springer resolution): for Kirillov-Reshetikhin modules of simply-laced quantum affine algebras, we characterize explicitly the Drinfeld polynomials corresponding to the small resolutions. We use an elimination...
Solving the sextic by iteration: a study in complex geometry and dynamics.
Some results on the topology of varieties dominated by Cn.
Some topological aspects of C* actions on compact Kaehler manifolds.
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.
Stability and equivariant maps.
Stability of pencils of plane quartic curves
In questa nota si danno dei criteri per la stabilità di fasci di quartiche piane.
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.
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.
Supersingular curves of genus two and class numbers
Sur la géométrie des variétés sphériques.