On spherical ideals of Borel subalgebras

Abstract.

The goal of this paper is to extend some previous results on abelian ideals of Borel subalgebras to so-called spherical ideals of ${\frak b}.$ These are ideals ${\frak c}$ of ${\frak b}$ such that their G-saturation $G \cdot {\frak c}$ is a spherical G-variety. We classify all maximal spherical ideals of ${\frak b}$ for all simple G.