Bergman kernels over polarized K\"ahler manifolds, Bergman logarithmic flatness, and a question of Lu-Tian

TL;DR

This paper investigates Bergman kernels on polarized Kähler manifolds, establishing conditions for logarithmic flatness and answering a question of Lu-Tian, with implications for the geometry of circle bundles over such manifolds.

Contribution

It provides a localization result for Bergman kernels and characterizes when they lack logarithmic singularities, addressing a question posed by Lu and Tian.

Findings

Established a localization result for the Bergman kernel of the disk bundle.

Derived a necessary and sufficient condition for the absence of logarithmic singularities.

Showed that compact, locally homogeneous Kähler manifolds have Bergman logarithmically flat circle bundles.

Abstract

Let $M$ be a complete K\"ahler manifold, and let $(L, h) \to M$ be a positive line bundle inducing a K\"ahler metric $g$ on $M$. We study two Bergman kernels in this setting: the Bergman kernel of the disk bundle of the dual line bundle $(L^*, h^*)$, and the Bergman kernel of the line bundle $(L^k, h^k)$, $k\geq 1$, twisted by the canonical line bundle of $(M, g)$. We first prove a localization result for the former Bergman kernel. Then we establish a necessary and sufficient condition for this Bergman kernel to have no logarithmic singularity, expressed in terms of the Tian-Yau-Zelditch-Catlin type expansion of the latter Bergman kernel. This result, in particular, answers a question posed by Lu and Tian. As an application, we show that if $(M, g)$ is compact and locally homogeneous, then the circle bundle of $(L^*, h^*)$ is necessarily Bergman logarithmically flat.