A Dixmier theorem for Poisson enveloping algebras

Abstract

We consider a skew-symmetric $n$-ary bracket on the polynomial algebra $K[x_1,\dots ,x_n,x_{n+1}]$ ($n\ge 2$) over a field $K$ of characteristic zero defined by $\{a_1,\dots ,a_n\}=J(a_1,\dots ,a_n,C)$, where $C$ is a fixed element of $K[x_1,\dots ,x_n,x_{n+1}]$ and $J$ is the Jacobian. If $n=2$ then this bracket is a Poisson bracket and if $n\ge 3$ then it is an $n$-Lie-Poisson bracket on $K[x_1,\dots ,x_n,x_{n+1}]$. We describe the center of the corresponding $n$-Lie-Poisson algebra and show that the quotient algebra $K[x_1,\dots ,x_n,x_{n+1}]/(C-\lambda )$, where $(C-\lambda )$ is the ideal generated by $C-\lambda$, $0\ne \lambda \in K$, is a simple central $n$-Lie-Poisson algebra if $C$ is a homogeneous polynomial that is not a proper power of any nonzero polynomial. This construction includes the quotients $P({\mathrm{sl}}_2(K))/(C-\lambda )$ of the Poisson enveloping algebra $P({\mathrm{sl}}_2(K))$ of the simple Lie algebra ${\mathrm{sl}}_2(K)$, where $C$ is the standard Casimir element of ${\mathrm{sl}}_2(K)$ in $P({\mathrm{sl}}_2(K))$. It is also proven that the quotients $P(\mathbb{M})/(C-\lambda )$ of the Poisson enveloping algebra $P(\mathbb{M})$ of the exceptional simple seven dimensional Malcev algebra $\mathbb{M}$ are central simple.

19 pages