Families of elliptic curves over the four-pointed configuration space and exceptional sequences for the braid group on four strands

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Hauptverfasser: Chen, William Y., Salter, Nick
Format: Preprint
Veröffentlicht: 2024
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author Chen, William Y.
Salter, Nick
author_facet Chen, William Y.
Salter, Nick
contents We show that the configuration space of four unordered points in $\mathbb{C}$ with barycenter 0 is isomorphic to the space of triples $(E,Q,ω)$, where $E$ is an elliptic curve, $Q\in E^\circ$ a nonzero point, and $ω$ a nonzero holomorphic differential on $E$. At the level of fundamental groups, our construction unifies two classical exceptional exact sequences involving the braid group $B_4$: namely, the sequence $1\rightarrow F_2\rightarrow B_4\rightarrow B_3\rightarrow 1$, where $F_2$ is a free group of rank 2, related to Ferrari's solution of the quartic, and the sequence $1\rightarrow \mathbb{Z} \rightarrow B_4\rightarrow\operatorname{Aut}^+(F_2)\rightarrow 1$ of Dyer-Formanek-Grossman.
format Preprint
id arxiv_https___arxiv_org_abs_2402_11081
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Families of elliptic curves over the four-pointed configuration space and exceptional sequences for the braid group on four strands
Chen, William Y.
Salter, Nick
Algebraic Geometry
Geometric Topology
We show that the configuration space of four unordered points in $\mathbb{C}$ with barycenter 0 is isomorphic to the space of triples $(E,Q,ω)$, where $E$ is an elliptic curve, $Q\in E^\circ$ a nonzero point, and $ω$ a nonzero holomorphic differential on $E$. At the level of fundamental groups, our construction unifies two classical exceptional exact sequences involving the braid group $B_4$: namely, the sequence $1\rightarrow F_2\rightarrow B_4\rightarrow B_3\rightarrow 1$, where $F_2$ is a free group of rank 2, related to Ferrari's solution of the quartic, and the sequence $1\rightarrow \mathbb{Z} \rightarrow B_4\rightarrow\operatorname{Aut}^+(F_2)\rightarrow 1$ of Dyer-Formanek-Grossman.
title Families of elliptic curves over the four-pointed configuration space and exceptional sequences for the braid group on four strands
topic Algebraic Geometry
Geometric Topology
url https://arxiv.org/abs/2402.11081