On the Commuting variety of a reductive Lie algebra and other related varieties

Abstract

The nilpotent cone of a reductive Lie algebra has a desingularization given by thecotangent bundle of the flag variety. Analogously, the nullcone of a cartesianpower of the algebra has a desingularization given by a vector bundle over theflag variety. As for the nullcone, the subvariety of elements whose componentsare in a same Borel subalgebra, has a desingularization given by a vector bundle overthe flag variety. In this note, some properties of these varieties are given. Forthe study of the commuting variety, the analogous variety to the flag variety isthe closure in the Grassmannian of the set of Cartan subalgebras. So someproperties of this variety are given. In particular, it is smooth in codimension $1$.We introduce the generalized isospectral commuting varieties and give some properties.Furthermore, desingularizations of these varieties are given by fiber bundles over adesingularization of the closure in the grassmannian of the set of Cartan subalgebrascontained in a given Borel subalgebra.