Hyperbolicity and fundamental groups of complex quasi-projective varieties (III): applications

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Hauptverfasser: Cadorel, Benoit, Deng, Ya, Yamanoi, Katsutoshi
Format: Preprint
Veröffentlicht: 2025
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author Cadorel, Benoit
Deng, Ya
Yamanoi, Katsutoshi
author_facet Cadorel, Benoit
Deng, Ya
Yamanoi, Katsutoshi
contents This paper is Part III of a series of three. We begin by introducing the notion of $h$-special varieties, which can be seen as varieties "chain-connected by the Zariski closures of entire curves." We prove that if $X$ is either a special complex quasi-projective variety in the sense of Campana or an $h$-special variety, then for any linear representation $\varrho:π_1(X)\to \mathrm{GL}_N(\mathbb{C})$, the image $\varrho(π_1(X))$ is virtually nilpotent. We also provide examples showing that this result is sharp, leading to a revised form of Campana's abelianity conjecture for smooth quasi-projective varieties. In addition, we prove a structure theorem for quasi-projective varieties with big and semisimple representations of the fundamental groups, thereby addressing a conjecture by Kollár in 1995. We also construct several examples of quasi-projective varieties that are special and $h$-special, highlighting certain atypical properties of the non-compact case in contrast with the projective setting.
format Preprint
id arxiv_https___arxiv_org_abs_2512_20360
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Hyperbolicity and fundamental groups of complex quasi-projective varieties (III): applications
Cadorel, Benoit
Deng, Ya
Yamanoi, Katsutoshi
Algebraic Geometry
Complex Variables
This paper is Part III of a series of three. We begin by introducing the notion of $h$-special varieties, which can be seen as varieties "chain-connected by the Zariski closures of entire curves." We prove that if $X$ is either a special complex quasi-projective variety in the sense of Campana or an $h$-special variety, then for any linear representation $\varrho:π_1(X)\to \mathrm{GL}_N(\mathbb{C})$, the image $\varrho(π_1(X))$ is virtually nilpotent. We also provide examples showing that this result is sharp, leading to a revised form of Campana's abelianity conjecture for smooth quasi-projective varieties. In addition, we prove a structure theorem for quasi-projective varieties with big and semisimple representations of the fundamental groups, thereby addressing a conjecture by Kollár in 1995. We also construct several examples of quasi-projective varieties that are special and $h$-special, highlighting certain atypical properties of the non-compact case in contrast with the projective setting.
title Hyperbolicity and fundamental groups of complex quasi-projective varieties (III): applications
topic Algebraic Geometry
Complex Variables
url https://arxiv.org/abs/2512.20360