Pieri's Formula Via Explicit Rational Equivalence

Abstract

We present a new geometric proof of Pieri's formula, exhibiting an explicit chain of rational equivalences from a suitable sum of distinct Schubert varieties to the intersection of a Schubert variety with a special Schubert variety. The geometry of these rational equivalences indicate a link to a combinatorial proof of Pieri's formula using Schensted insertion. This version includes an example to illustrate the proof.