Compositions of Schubert Problems

A composition of Schubert problems is a construction
that takes two Schubert problems on possibly different
Grassmannians and gives a Schubert problem on a larger
Grassmannian whose number of solutions is the product of
the numbers of solutions of the original problems.  This 
generalizes a construction that was discovered while 
classifying Schubert problems with imprimitive Galois 
groups.

I will explain this construction and the product formula,
which has both an algebraic and a bijective proof. I will
also discuss how this construction is related to Galois 
groups of Schubert problems.  This is joint work with 
Li Ying and Robert Williams.