A Geometric Definition Of Schubert Polynomials and Dual Schubert   Polynomials For Classical Lie Groups
  In this paper, we first discuss the topological properties of projective Stiefel manifolds, we compute their cohomology rings and classify their cohomology endomorphisms; Then by embedding the flag manifold of a classical Lie group into its corresponding infinite dimensional projective Stiefel manifold(which is homotopic to the product of infinite dimensional complex projective space $\mathbb{C}P^{\infty}$), we define the Schubert polynomials and dual Schubert polynomials. Finally we discuss the property and the computation of these polynomials. 
Zhao Xu-an and Gao Hongzhu
math.AT math.CO