Faithful Burau-like representations of some rank two Garside groups and torus knot groups

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1. Verfasser: Gobet, Thomas
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Veröffentlicht: 2025
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author Gobet, Thomas
author_facet Gobet, Thomas
contents We give a method to produce faithful representations of the groups $G(n,m)=\langle X, Y \ \vert \ X^m = Y^n \rangle$ in $\mathrm{GL}_2(\mathbb{C}[t^{\pm 1}, q^{\pm 1}])$. These groups are Garside groups and the Garside normal forms of elements of the corresponding monoid can be explicitly recovered from the matrices, in the spirit of Krammer's proof of the linearity of Artin's braid groups. We use this method to construct several explicit faithful representations of the above groups, among which a representation which generalizes the reduced Burau representation of $B_3 \cong G(2,3)$ to a large family of groups of the form $G(n,m)$ with $n$, $m$ coprime (which are torus knot groups). Like the Burau representation, this representation specializes to a representation of a reflection-like quotient that we previously introduced, called \textit{$2$-toric reflection group}. As a byproduct we get a "Burau representation" for some exceptional complex braid groups, which also shows that the latter embed into their Hecke algebra.
format Preprint
id arxiv_https___arxiv_org_abs_2506_21340
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Faithful Burau-like representations of some rank two Garside groups and torus knot groups
Gobet, Thomas
Group Theory
Geometric Topology
Quantum Algebra
Representation Theory
We give a method to produce faithful representations of the groups $G(n,m)=\langle X, Y \ \vert \ X^m = Y^n \rangle$ in $\mathrm{GL}_2(\mathbb{C}[t^{\pm 1}, q^{\pm 1}])$. These groups are Garside groups and the Garside normal forms of elements of the corresponding monoid can be explicitly recovered from the matrices, in the spirit of Krammer's proof of the linearity of Artin's braid groups. We use this method to construct several explicit faithful representations of the above groups, among which a representation which generalizes the reduced Burau representation of $B_3 \cong G(2,3)$ to a large family of groups of the form $G(n,m)$ with $n$, $m$ coprime (which are torus knot groups). Like the Burau representation, this representation specializes to a representation of a reflection-like quotient that we previously introduced, called \textit{$2$-toric reflection group}. As a byproduct we get a "Burau representation" for some exceptional complex braid groups, which also shows that the latter embed into their Hecke algebra.
title Faithful Burau-like representations of some rank two Garside groups and torus knot groups
topic Group Theory
Geometric Topology
Quantum Algebra
Representation Theory
url https://arxiv.org/abs/2506.21340