For some values of the degrees of the equations, we show, using geometric invariant theory, that the coarse moduli space of smooth complete intersections in is quasi-projective.
On considère une extension finie de , avec un nombre premier, un sous-groupe d’indice fini de et le groupe . Nous montrons que admet un sous-groupe -Zariski-dense dont toutes les matrices ont leur spectre inclus dans si et seulement si soit est dans le sous-groupe , soit n’est pas congru à 2 modulo 4.
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.
In questa nota si danno dei criteri per la stabilità di fasci di quartiche piane.
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...
The rationality of a stably rational torus with a cyclic splitting field is proved.