Towards a characterization of toric hyperk\"{a}hler varieties among symplectic singularities II

Abstract

This is a continuation of arXiv: 2408.03012. We answer affirmatively Question 5.10 posed in the previous article. More precisely, let $(X, \omega)$ be a conical symplectic variety of dimension $2n$ with $wt(\omega) = 2$, which has a projective symplectic resolution. Assume that $X$ admits an effective Hamiltonian action of an $n$-dimensional algebraic torus $T^n$, compatible with the conical $\mathbf{C}^*$-action. Then we prove that there is a $T^n$-equivariant algebraic isomorphism $(X, \omega) \cong (Y(A,0), \omega_{Y(A,0)})$ for a toric hyperkahler variety $Y(A, 0)$ with $A$ unimodular.