Note that this talk will be on Monday!
Ribbon Schur functions are skew Schur functions corresponding
to "ribbon" or "border strip" Ferrers shapes, namely, connected diagrams
with no 2 x 2 squares. Those with n boxes naturally correspond to
integer compositions of n. We give necessary and sufficient conditions
for two such compositions to give identical Schur functions. This
involves a notion of combining compositions that corresponds to computing
descent sets in tensor products of permutations.