Special Kähler-Ricci potentials on compact Kähler manifolds

Abstract

A special Kähler-Ricci potential on a Kähler manifold is any nonconstant $C^{\infty }$ function $\tau$ such that $J(\nabla \tau )$ is a Killing vector field and, at every point with $d\tau \ne 0$, all nonzero tangent vectors orthogonal to $\nabla \tau$ and $J(\nabla \tau )$ are eigenvectors of both $\nabla d\tau$ and the Ricci tensor. For instance, this is always the case if $\tau$ is a nonconstant $C^{\infty }$ function on a Kähler manifold $(M,g)$ of complex dimension $m>2$ and the metric $\tilde{g}=g/{\tau }^2$, defined wherever $\tau \ne 0$, is Einstein. (When such $\tau$ 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.

45 pages, AMSTeX, submitted to Journal für die reine und angewandte Mathematik