Adiabatic Limit and Deformations of Complex Structures

TL;DR

This paper extends the adiabatic limit technique to complex structures, proving that the deformation limit of Moishezon manifolds remains Moishezon, and introduces new tools involving holomorphic vector bundles and a relaxed notion of Gauduchon metrics.

Contribution

It introduces a novel approach to analyze complex structure deformations using adiabatic limits and defines a new class of Gauduchon metrics, expanding understanding of complex manifold degenerations.

Findings

Deformation limits of Moishezon manifolds are Moishezon.

Constructs a holomorphic vector bundle over  for each complex manifold.

Introduces the concept of $E_r$-sG metrics, generalizing strongly Gauduchon metrics.

Abstract

Based on our recent adaptation of the adiabatic limit construction to the case of complex structures, we prove the fact that the deformation limiting manifold of any holomorphic family of Moishezon manifolds is Moishezon. Two new ingredients, hopefully of independent interest, are introduced. The first one associates with every compact complex manifold $X$, in every degree $k$, a holomorphic vector bundle over $\C$ of rank equal to the $k$-th Betti number of $X$. This vector bundle, previously given an algebraic construction in the literature, shows that the degenerating page of the Fr\"olicher spectral sequence of $X$ is the holomorphic limit, as $h\in\C^\star$ tends to $0$, of the $d_h$-cohomology of $X$, where $d_h=h\partial + \bar\partial$. A relative version of this vector bundle is then associated with every holomorphic family of compact complex manifolds. The second ingredient is a relaxation of the notion of strongly Gauduchon (sG) metric that we introduced in 2009. For a given positive integer $r$, a Gauduchon metric $\gamma$ on an $n$-dimensional compact complex manifold $X$ is said to be $E_r$-sG if $\partial\gamma^{n-1}$ represents the zero cohomology class on the $r$-th page of the Fr\"olicher spectral sequence of $X$. Strongly Gauduchon metrics coincide with $E_1$-sG metrics.