2 00 7 Horn recursion for a new product in the

Horn recursion is a term used to describe when non-vanishing products of Schubert classes in the cohomology of flag varieties G/P are characterized by inequalities parameterized by similar non-vanishing products in the cohomology of ”smaller” flag varieties. We consider the partial flag variety SLn/P and find that H (SLn/P ) exhibits Horn recursion on a certain deformation of the cup product. We also show that if a product of Schubert classes is non-vanishing on this deformation, then the associated structure constant can be written in terms of structure constants coming from induced Grassmannians.