## Algebraic Geometry Seminar: Colleen Robles

- Date: 10/15/2012
- Time: 15:00

University of British Columbia

Singular loci of cominuscule Schubert varieties

The Schubert subvarieties of a rational homogeneous variety X are distinguished by the fact that their homology classes form an additive basis of the integer homology of X. In general, the Schubert varieties are singular.The cominuscule rational homogeneous varieties are those admitting the structure of a compact Hermitian symmetric space (eg. complex Grassmannians). In this case, type-dependent characterizations of the singular loci are known.I will discuss a type-independent description, by representation theoretic data, of the singular loci. The result is based on a characterization (joint with D. The) of the Schubert varieties by an non-negative integer and a marked Dynkin diagram.(If there is time left, I will discuss the project in which the integer-diagram characterization arose as a technical lemma. This work aims to determine whether or not the Schubert classes admit any algebraic representatives (other than the Schubert varieties). It is a remarkable consequence of Kostant's work that these algebraic representatives are solutions of a system of PDE; as a consequence, differential geometric techniques may be applied to this algebro-topological question.)

Location: ESB 2012