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Schubert polynomials and algebraic geometry

Schubert polynomials have an important geometrical interpretation as Schubert cycles. One now works in the quotient ring (Flag ) of the ring of polynomials modulo the ideal generated by the symmetric polynomials without constant term, which is the so-called ring of coinvariants of the symmetric group. This ring can be interpreted as the cohomology ring , or Chow ring, of the variety of complete flags in . With this interpretation, the class of the Schubert polynomial is the Poincaré dual of the Schubert cycle . The flag manifold is equipped with tautological line bundles , whose respective first Chern classes are equal to the classes of modulo the ideal .

The double Schubert polynomials also have a geometrical interpretation. When the variables and are interpreted as Chern classes of certain line bundles over a variety M, they give the cohomology classes corresponding to various degeneracy loci of maps of flagged bundles over M.

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