Invariant polynomials on truncated multicurrent algebras

Abstract

We construct invariant polynomials on truncated multicurrent algebras, which are Lie algebras of the form $\mathfrak{g}{\otimes }_{\mathbb{F}}\mathbb{F}[t_1,\dots ,t_{\ell }]/I$, where $\mathfrak{g}$ is a finite-dimensional Lie algebra over a field $\mathbb{F}$ of characteristic zero, and $I$ is a finite-codimensional ideal of $\mathbb{F}[t_1,\dots ,t_{\ell }]$ generated by monomials. In particular, when $\mathfrak{g}$ is semisimple and $\mathbb{F}$ is algebraically closed, we construct a set of algebraically independent generators for the algebra of invariant polynomials. In addition, we describe a transversal slice to the space of regular orbits in $\mathfrak{g}{\otimes }_{\mathbb{F}}\mathbb{F}[t_1,\dots ,t_{\ell }]/I$. As an application of our main result, we show that the center of the universal enveloping algebra of $\mathfrak{g}{\otimes }_{\mathbb{F}}\mathbb{F}[t_1,\dots ,t_{\ell }]/I$ acts trivially on all irreducible finite-dimensional representations provided $I$ has codimension at least two.

17 pages; v2: Corrected statements of Proposition 5.7 and Remark 5.8; v3: Minor changes, published version