Random walks and the symplectic representation of the braid group

Fuente: arXiv
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Autori principali: Soret, Marc, Ville, Marina
Natura: Preprint
Pubblicazione: 2022
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author Soret, Marc
Ville, Marina
author_facet Soret, Marc
Ville, Marina
contents We consider the symplectic representation $ρ_n$ of a braid group $B(n)$ in $Sp(2l,\mathbb{Z})$, for $l=\Big[\dfrac{n-1}{2}\Big]$. If $P$ is a polynomial on the $4l^2$ coefficients of the matrices in $Sp(2l,\mathbb{Z})$, we show that the set $\{β\in B(n): P(ρ_n(β))=0\}$ is transient for non degenerate random walks on $B(n)$. We derive that the $n$-braids $β$ which close into a loop $\hatβ$ with $0<|det({\hatβ})|\leq C$ for some constant $C$ form a transient set. And given a prime number $p$, we show that the probability for a given braid to close in a $p$-colorable loop is greater than $\dfrac{1}{p}$. We also derive that for a random $3$-braid, the quasipositive links $(βσ_iβ^{-1}σ_j)^p$ have zero signature for every integer $p$ and $1\leq i,j\leq 2$. \\ As an example of such braids, we investigate the signature of the Lissajous toric knots $3$-braids.
format Preprint
id arxiv_https___arxiv_org_abs_2203_00984
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Random walks and the symplectic representation of the braid group
Soret, Marc
Ville, Marina
Geometric Topology
57K10, 57K14, 60B15, 60B20, 60G50
We consider the symplectic representation $ρ_n$ of a braid group $B(n)$ in $Sp(2l,\mathbb{Z})$, for $l=\Big[\dfrac{n-1}{2}\Big]$. If $P$ is a polynomial on the $4l^2$ coefficients of the matrices in $Sp(2l,\mathbb{Z})$, we show that the set $\{β\in B(n): P(ρ_n(β))=0\}$ is transient for non degenerate random walks on $B(n)$. We derive that the $n$-braids $β$ which close into a loop $\hatβ$ with $0<|det({\hatβ})|\leq C$ for some constant $C$ form a transient set. And given a prime number $p$, we show that the probability for a given braid to close in a $p$-colorable loop is greater than $\dfrac{1}{p}$. We also derive that for a random $3$-braid, the quasipositive links $(βσ_iβ^{-1}σ_j)^p$ have zero signature for every integer $p$ and $1\leq i,j\leq 2$. \\ As an example of such braids, we investigate the signature of the Lissajous toric knots $3$-braids.
title Random walks and the symplectic representation of the braid group
topic Geometric Topology
57K10, 57K14, 60B15, 60B20, 60G50
url https://arxiv.org/abs/2203.00984