Classification of indecomposable reflexive modules on quotient singularities through Atiyah--Patodi--Singer theory

Fuente: arXiv
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Auteurs principaux: Nevárez, José Antonio Arciniega, Cisneros-Molina, José Luis, Velázquez, Agustín Romano
Format: Preprint
Publié: 2025
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author Nevárez, José Antonio Arciniega
Cisneros-Molina, José Luis
Velázquez, Agustín Romano
author_facet Nevárez, José Antonio Arciniega
Cisneros-Molina, José Luis
Velázquez, Agustín Romano
contents In [20] Esnault asked whether on a general quotient surface singularity the rank and the first Chern class distinguish isomorphism classes of indecomposable reflexive modules. Wunram gave a contraexample in [46] showing two different full shaves on a quotient singularity, with the same rank and the same first Chern class. In this article, we prove that irreducible reflexive modules over quotient surface singularities are determined by the rank, first Chern class and the Atiyah-Patodi-Singer $\tildeξ$-invariant [5], except for the case of rank $2$ indecomposable reflexive modules over dihedral quotient surface singularities $\mathbb{D}_{n,q}$ with $\gcd(m,2)=2$, which we conjecture to follow the same pattern. To prove the classification theorem, first we prove that every spherical $3$-manifold with non-trivial fundamental group appears as the link of a quotient surface singularity, and that indecomposable flat vector bundles over spherical $3$-manifolds are classified by their rank, first and second Cheeger-Chern-Simons classes, with the exception of the aforementioned case.
format Preprint
id arxiv_https___arxiv_org_abs_2504_21204
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Classification of indecomposable reflexive modules on quotient singularities through Atiyah--Patodi--Singer theory
Nevárez, José Antonio Arciniega
Cisneros-Molina, José Luis
Velázquez, Agustín Romano
Algebraic Geometry
In [20] Esnault asked whether on a general quotient surface singularity the rank and the first Chern class distinguish isomorphism classes of indecomposable reflexive modules. Wunram gave a contraexample in [46] showing two different full shaves on a quotient singularity, with the same rank and the same first Chern class. In this article, we prove that irreducible reflexive modules over quotient surface singularities are determined by the rank, first Chern class and the Atiyah-Patodi-Singer $\tildeξ$-invariant [5], except for the case of rank $2$ indecomposable reflexive modules over dihedral quotient surface singularities $\mathbb{D}_{n,q}$ with $\gcd(m,2)=2$, which we conjecture to follow the same pattern. To prove the classification theorem, first we prove that every spherical $3$-manifold with non-trivial fundamental group appears as the link of a quotient surface singularity, and that indecomposable flat vector bundles over spherical $3$-manifolds are classified by their rank, first and second Cheeger-Chern-Simons classes, with the exception of the aforementioned case.
title Classification of indecomposable reflexive modules on quotient singularities through Atiyah--Patodi--Singer theory
topic Algebraic Geometry
url https://arxiv.org/abs/2504.21204