Equivariant Kähler model for Fujiki's class

Abstract

Let $X$ be a compact complex manifold in Fujiki's class $\mathcal{C}$, i.e., admitting a big $(1,1)$-class $[\alpha ]$. Consider $\text{Aut}(X)$ the group of biholomorphic automorphisms and ${\text{Aut}}_{[\alpha ]}(X)$ the subgroup of automorphisms preserving the class $[\alpha ]$ via pullback. We show that $X$ admits an ${\text{Aut}}_{[\alpha ]}(X)$-equivariant Kähler model: there is a bimeromorphic holomorphic map $\sigma :\tilde{X}\to X$ from a Kähler manifold $\tilde{X}$ such that ${\text{Aut}}_{[\alpha ]}(X)$ lifts holomorphically via $\sigma$. There are several applications. We show that ${\text{Aut}}_{[\alpha ]}(X)$ is a Lie group with only finitely many components. This generalizes an early result of Lieberman and Fujiki on the Kähler case. We also show that every torsion subgroup of $\text{Aut}(X)$ is almost abelian, and $\text{Aut}(X)$ is finite if it is a torsion group.

14 pages, comments are welcome!