Kohnert's rule for flagged Schur modules

Flagged Schur modules generalize the irreducible representations of general linear group under action Borel subalgebra. Their characters include many important generalizations polynomials, such as Demazure characters, flagged skew and Schubert polynomials. In this paper, we prove can be computed using a simple combinatorial algorithm due to Kohnert if only indexing diagram is northwest. This gives new proof that are nonnegative sums representation theoretic interpretation for