Existence of Equivariant Models of Spherical Varieties and Other <i>G</i>-varieties

Spherical Varieties and Existence of Invariant K

Equivariant sheaves on some spherical varieties

In this announcement we describe categories of equivariant vector bundles on certain “spherical” varieties. Our description is in linear-algebra terms: vector spaces equipped with filtrations, group and Lie-algebra actions, and linear maps preserving these structures. The two parents of our description are i) the description of G-equivariant vector bundles on homogeneous spaces G/H as H-represe...

Equivariant Sheaves on Flag Varieties

We show that the Borel-equivariant derived category of sheaves on the flag variety of a complex reductive group is equivalent to the perfect derived category of dg modules over the extension algebra of the direct sum of the simple equivariant perverse sheaves. This proves a conjecture of Soergel and Lunts in the case of flag varieties.

Toric Degenerations of Spherical Varieties

We prove that any affine, resp. polarized projective, spherical variety admits a flat degeneration to an affine, resp. polarized projective, toric variety. Motivated by Mirror Symmetry, we give conditions for the limit toric variety to be a Gorenstein Fano, and provide many examples. We also provide an explanation for the limits as boundary points of the moduli space of stable pairs whose exist...

Boundedness of Spherical Fano Varieties

Classically, G. Fano proved that the family of (smooth, anticanonically embedded) Fano 3-dimensional varieties is bounded, and moreover provided their classification, later completed by V.A. Iskovskikh, S. Mukai and S. Mori. For singular Fano varieties with log terminal singularities, there are two basic boundedness conjectures: Index Boundedness and the much stronger ǫ-lt Boundedness. The ǫ-lt...