A note on \'etale representations from nilpotent orbits

Abstract

A linear \'etale representation of a complex algebraic group $G$ is given by a complex algebraic $G$-module $V$ such that $G$ has a Zariski-open orbit on $V$ and $\dim G=\dim V$. A current line of research investigates which \'etale representations can occur for reductive algebraic groups. Since a complete classification seems out of reach, it is of interest to find new examples of \'etale representations for such groups. The aim of this note is to describe two classical constructions of Vinberg and of Bala & Carter for nilpotent orbit classifications in semisimple Lie algebras, and to determine which reductive groups and \'etale representations arise in these constructions. We also explain in detail the relation between these two~constructions.