We give a short introduction to the problem of classification of spherical varieties, by presenting the Luna conjecture about the classification of wonderful varieties and illustrating some of the related currently known results.
In the setting of strict wonderful varieties we prove Luna’s conjecture, saying that wonderful varieties are classified by combinatorial objects, the so-called spherical systems. In particular, we prove that primitive strict wonderful varieties are mostly obtained from symmetric spaces, spherical nilpotent orbits and model spaces. To make the paper as self-contained as possible, we also gather some known results on these families and more generally on wonderful varieties.
2000 Mathematics Subject Classification: Primary 14E15; Secondary 14C05,14L30.In this note we attempt to generalize a few statements drawn from the 3-dimensional McKay correspondence to the case of a cyclic group not in SL(3, C). We construct a smooth, discrepant resolution of the cyclic, terminal quotient singularity of type 1/r(1,1,r−1), which turns out to be isomorphic to Nakamura’s G-Hilbert scheme. Moreover we explicitly describe tautological bundles and use them to construct a dual basis to...
Nous construisons explicitement la normalisation de la compactification de Bott-Samelson-Demazure-Hansen des variétés de Deligne-Lusztig dans leur revêtement et retrouvons ainsi un résultat de Deligne-Lusztig sur la monodromie locale autour des diviseurs de la compactification.
On calcule par des méthodes arithmétiques le groupe de Brauer non ramifié des espaces homogènes de groupes algébriques linéaires sur différents corps. Les formules obtenues font intervenir l’hypercohomologie de complexes de groupes de type multiplicatif.
A compact complex space is called complex-symmetric with respect to a subgroup of the group , if each point of is isolated fixed point of an involutive automorphism of . It follows that is almost -homogeneous. After some examples we classify normal complex-symmetric varieties with reductive. It turns out that is a product of a Hermitian symmetric space and a compact torus embedding satisfying some additional conditions. In the smooth case these torus embeddings are classified using...
Soit une involution de l’algèbre de Lie semi-simple de dimension finie et la décomposition de Cartan associée. La variété commutante nilpotente de l’algèbre de Lie symétrique est formée des paires d’éléments nilpotents de tels que . Il est conjecturé que cette variété est équidimensionnelle et que ses composantes irréductibles sont indexées par les orbites d’éléments -distingués. Cette conjecture a été démontrée par A. Premet dans le cas avec . Dans ce travail, nous la prouvons...