Local Monodromy of Constructible Sheaves

Fuente: arXiv
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Main Authors: Nori, Madhav V., Patel, Deepam
Format: Preprint
Published: 2026
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author Nori, Madhav V.
Patel, Deepam
author_facet Nori, Madhav V.
Patel, Deepam
contents Given a morphism $f: X \rightarrow S$ of complex algebraic varieties and a constructible sheaf $\mathcal{G}$ on $X$, we compute the local monodromy of $Rf_*(\mathcal{G})$ and $Rf_!(\mathcal{G})$ in terms of the local monodromy of $\mathcal{G}$. Our results generalize previous results by Brieskorn, Borel, Clemens, Deligne, Landsman, Griffiths, Grothendieck, and Kashiwara in the setting of quasi-unipotent sheaves. In the following, we consider the general setting of sheaves of $R$-modules for a commutative noetherian ring $R$, and give applications to computing local monodromy of abelian covers in a uniform manner. We also obtain applications in the context of `generalized Alexander modules' and intersection cohomology with torsion coefficients.
format Preprint
id arxiv_https___arxiv_org_abs_2601_02178
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Local Monodromy of Constructible Sheaves
Nori, Madhav V.
Patel, Deepam
Algebraic Geometry
Given a morphism $f: X \rightarrow S$ of complex algebraic varieties and a constructible sheaf $\mathcal{G}$ on $X$, we compute the local monodromy of $Rf_*(\mathcal{G})$ and $Rf_!(\mathcal{G})$ in terms of the local monodromy of $\mathcal{G}$. Our results generalize previous results by Brieskorn, Borel, Clemens, Deligne, Landsman, Griffiths, Grothendieck, and Kashiwara in the setting of quasi-unipotent sheaves. In the following, we consider the general setting of sheaves of $R$-modules for a commutative noetherian ring $R$, and give applications to computing local monodromy of abelian covers in a uniform manner. We also obtain applications in the context of `generalized Alexander modules' and intersection cohomology with torsion coefficients.
title Local Monodromy of Constructible Sheaves
topic Algebraic Geometry
url https://arxiv.org/abs/2601.02178