The pro-étale fundamental group of singular schemes

Fuente: arXiv
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Main Authors: Yu, Jiu-Kang, Zhang, Lei
Format: Preprint
Published: 2026
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author Yu, Jiu-Kang
Zhang, Lei
author_facet Yu, Jiu-Kang
Zhang, Lei
contents We compute the pro-étale fundamental group of a connected Nagata J-2 scheme in terms of the étale fundamental groups of the normalizations of its irreducible components and a discrete free group. The result generalizes a formula of E. Lavanda for semi-stable curves and relies on a combination of proper descent techniques for étale morphisms and a combinatorial van Kampen construction for Noohi groups. As a by-product we characterize when a continuous representation of the pro-étale fundamental group factors through a discrete quotient.
format Preprint
id arxiv_https___arxiv_org_abs_2605_20598
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The pro-étale fundamental group of singular schemes
Yu, Jiu-Kang
Zhang, Lei
Algebraic Geometry
Algebraic Topology
Number Theory
We compute the pro-étale fundamental group of a connected Nagata J-2 scheme in terms of the étale fundamental groups of the normalizations of its irreducible components and a discrete free group. The result generalizes a formula of E. Lavanda for semi-stable curves and relies on a combination of proper descent techniques for étale morphisms and a combinatorial van Kampen construction for Noohi groups. As a by-product we characterize when a continuous representation of the pro-étale fundamental group factors through a discrete quotient.
title The pro-étale fundamental group of singular schemes
topic Algebraic Geometry
Algebraic Topology
Number Theory
url https://arxiv.org/abs/2605.20598