  Let HH_{ab}(H) be the equivariant Hilbert scheme parametrizing the zero
dimensional subschemes of the affine plane k^2, fixed under the one dimensional
torus T_{ab}={(t^{-b},t^a), t\in k^*} and whose Hilbert function is H. This
Hilbert scheme admits a natural stratification in Schubert cells which extends
the notion of Schubert cells on Grassmannians. However, the incidence relations
between the cells become more complicated than in the case of Grassmannians. In
this paper, we give a necessary condition for the closure of a cell to meet
another cell. In the particular case of Grassmannians, it coincides with the
well known necessary and sufficient incidence condition. There is no known
example showing that the condition wouldn't be sufficient.
