On a sequence of singular ball quotient surfaces on the line $K^2=9χ-18$

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Hauptverfasser: Rito, Carlos, Roulleau, Xavier
Format: Preprint
Veröffentlicht: 2025
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author Rito, Carlos
Roulleau, Xavier
author_facet Rito, Carlos
Roulleau, Xavier
contents Starting from computer experiments with the fundamental group of the Cartwright--Steger surface, we construct an infinite tower $(X_n)_{n\ge 1}$ of normal projective surfaces obtained by successive $\mathbb Z/3$-Galois covers $X_{n}\to X_{n-1}$. For $n>1$, their minimal resolutions $\widetilde{X}_n$ lie on the line $K^2 = 9χ- 18$ (equivalently $c_1^2 = 3c_2 - 72$), which is parallel to the Bogomolov--Miyaoka--Yau line $K^2 = 9χ$ of ball quotients. We compute the fundamental groups for the first cases, showing that $π_1(\widetilde{X}_n)=1$ for $n=1,\ldots,5$. Motivated by the geometry of the construction, we conjecture that all $\widetilde{X}_n$ are simply connected.
format Preprint
id arxiv_https___arxiv_org_abs_2510_09588
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On a sequence of singular ball quotient surfaces on the line $K^2=9χ-18$
Rito, Carlos
Roulleau, Xavier
Algebraic Geometry
Primary 14J29, Secondary 14Q10, 20F05, 20F34
Starting from computer experiments with the fundamental group of the Cartwright--Steger surface, we construct an infinite tower $(X_n)_{n\ge 1}$ of normal projective surfaces obtained by successive $\mathbb Z/3$-Galois covers $X_{n}\to X_{n-1}$. For $n>1$, their minimal resolutions $\widetilde{X}_n$ lie on the line $K^2 = 9χ- 18$ (equivalently $c_1^2 = 3c_2 - 72$), which is parallel to the Bogomolov--Miyaoka--Yau line $K^2 = 9χ$ of ball quotients. We compute the fundamental groups for the first cases, showing that $π_1(\widetilde{X}_n)=1$ for $n=1,\ldots,5$. Motivated by the geometry of the construction, we conjecture that all $\widetilde{X}_n$ are simply connected.
title On a sequence of singular ball quotient surfaces on the line $K^2=9χ-18$
topic Algebraic Geometry
Primary 14J29, Secondary 14Q10, 20F05, 20F34
url https://arxiv.org/abs/2510.09588