Profinite almost rigidity in 3-manifolds

We prove that any compact, orientable 3-manifold with empty or toral boundary is profinitely almost rigid among all compact, orientable 3-manifolds. In other words, the profinite completion of its fundamental group determines its homeomorphism type to finitely many possibilities. Moreover, the profinite completion of the fundamental group of a mixed 3-manifold together with the peripheral structure uniquely determines the homeomorphism type of its Seifert part, i.e. the maximal graph manifold components in the JSJ-decomposition. On the other hand, without assigning the peripheral structure, the profinite completion of a mixed 3-manifold group may not uniquely determine the fundamental group of its Seifert part. The proof is based on JSJ-decomposition.

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Publication Details

Journal
Advances in Mathematics
Published
2025-09-02
DOI
https://doi.org/10.1016/j.aim.2025.110505
Primary Topic
Geometric and Algebraic Topology
Type
article
Field-Weighted Citation Impact
0.00
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article

Profinite almost rigidity in 3-manifolds

Xiaoyu Xu
Advances in Mathematics
Geometric and Algebraic Topology
article

Profinite almost rigidity in 3-manifolds

Xiaoyu Xu
article en

Abstract

We prove that any compact, orientable 3-manifold with empty or toral boundary is profinitely almost rigid among all compact, orientable 3-manifolds. In other words, the profinite completion of its fundamental group determines its homeomorphism type to finitely many possibilities. Moreover, the profinite completion of the fundamental group of a mixed 3-manifold together with the peripheral structure uniquely determines the homeomorphism type of its Seifert part, i.e. the maximal graph manifold components in the JSJ-decomposition. On the other hand, without assigning the peripheral structure, the profinite completion of a mixed 3-manifold group may not uniquely determine the fundamental group of its Seifert part. The proof is based on JSJ-decomposition.

Advances in MathematicsVol. 480
Peking University (CN), Peking University International Hospital (CN)
Openalex Percentile: Top 71%
Geometric and Algebraic Topology
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