Published online by Cambridge University Press: 20 February 2018
Varieties of the form $G\times S_{\!\text{reg}}$, where
$G$ is a complex semisimple group and
$S_{\!\text{reg}}$ is a regular Slodowy slice in the Lie algebra of
$G$, arise naturally in hyperkähler geometry, theoretical physics and the theory of abstract integrable systems. Crooks and Rayan [‘Abstract integrable systems on hyperkähler manifolds arising from Slodowy slices’, Math. Res. Let., to appear] use a Hamiltonian
$G$-action to endow
$G\times S_{\!\text{reg}}$ with a canonical abstract integrable system. To understand examples of abstract integrable systems arising from Hamiltonian
$G$-actions, we consider a holomorphic symplectic variety
$X$ carrying an abstract integrable system induced by a Hamiltonian
$G$-action. Under certain hypotheses, we show that there must exist a
$G$-equivariant variety isomorphism
$X\cong G\times S_{\!\text{reg}}$.