Gysin formulae on partial flag bundles
abstract: I would like to show a simple geometric proof
of some classical formulae computing the Gysin (or pushforward)
map for the projection of a Grassmann bundle (more generally,
a partial flag bundle) to its base. The formulae involve
Schur polynomials, and the proof uses equivariant localisation
to establish the connection between the geometric construction
and the combinatorial nature of the result.