Special Kähler-Ricci potentials on compact Kähler manifolds

Abstract

A special Kähler-Ricci potential on a Kähler manifold is any nonconstant $C^\infty$ function $τ$ such that $J(\nablaτ)$ is a Killing vector field and, at every point with $dτ\ne 0$, all nonzero tangent vectors orthogonal to $\nablaτ$ and $J(\nablaτ)$ are eigenvectors of both $\nabla dτ$ and the Ricci tensor. For instance, this is always the case if $τ$ is a nonconstant $C^\infty$ function on a Kähler manifold $(M,g)$ of complex dimension $m>2$ and the metric $\tilde g=g/τ^2$, defined wherever $τ\ne 0$, is Einstein. (When such $τ$ exists, $(M,g)$ may be called {\it almost-everywhere conformally Einstein}.) We provide a complete classification of compact Kähler manifolds with special Kähler-Ricci potentials and use it to prove a structure theorem for compact Kähler manifolds of any complex dimension $m>2$ which are almost-everywhere conformally Einstein.