From quantum Schubert polynomials to k-Schur functions via the Toda lattice

We show that Lapointe-Lascoux-Morse k-Schur functions (at t=1) and Fomin-Gelfand-Postnikov quantum Schubert polynomials can be obtained from each other by a rational substitution. This is based upon Kostant’s solution of the Toda lattice and Peterson’s work on quantum Schubert calculus.