Counting $SL(2,\mathbb{C})$ connections on Seifert-fibered spaces

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Main Author: Muñoz-Echániz, Juan
Format: Preprint
Published: 2025
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author Muñoz-Echániz, Juan
author_facet Muñoz-Echániz, Juan
contents We study the $SL(2, \mathbb{C})$ character variety of a Seifert-fibered homology $3$-sphere from the point of view of gauge theory. Namely, we introduce a class of perturbations of the $SL(2,\mathbb{C})$ Chern--Simons functional and prove a localisation result: the perturbed critical points either approach a compact subset of the $SL(2, \mathbb{C})$ character variety or else `escape to infinity'. Furthermore, the Euler characteristic and Poincaré polynomial of the stable locus of the character variety are obtained by suitably counting the localising critical points. As an application, we obtain formulae for the Euler characteristic and Poincaré polynomial of the stable locus of the $SL(2, \mathbb{C})$ character variety of a Seifert-fibered homology $3$-sphere. In particular, we prove that the Euler characteristic equals the Milnor number (divided by four) of any weighted-homogeneous isolated complete intersection singularity whose link is the given $3$-manifold.
format Preprint
id arxiv_https___arxiv_org_abs_2503_16370
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Counting $SL(2,\mathbb{C})$ connections on Seifert-fibered spaces
Muñoz-Echániz, Juan
Geometric Topology
Algebraic Geometry
Differential Geometry
We study the $SL(2, \mathbb{C})$ character variety of a Seifert-fibered homology $3$-sphere from the point of view of gauge theory. Namely, we introduce a class of perturbations of the $SL(2,\mathbb{C})$ Chern--Simons functional and prove a localisation result: the perturbed critical points either approach a compact subset of the $SL(2, \mathbb{C})$ character variety or else `escape to infinity'. Furthermore, the Euler characteristic and Poincaré polynomial of the stable locus of the character variety are obtained by suitably counting the localising critical points. As an application, we obtain formulae for the Euler characteristic and Poincaré polynomial of the stable locus of the $SL(2, \mathbb{C})$ character variety of a Seifert-fibered homology $3$-sphere. In particular, we prove that the Euler characteristic equals the Milnor number (divided by four) of any weighted-homogeneous isolated complete intersection singularity whose link is the given $3$-manifold.
title Counting $SL(2,\mathbb{C})$ connections on Seifert-fibered spaces
topic Geometric Topology
Algebraic Geometry
Differential Geometry
url https://arxiv.org/abs/2503.16370