Recognising conjugacy classes of Dehn twists on $\mathbb D_3$

Fuente: arXiv
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Main Authors: Atalan, Ferihe, Finashin, Sergey
Format: Preprint
Published: 2026
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author Atalan, Ferihe
Finashin, Sergey
author_facet Atalan, Ferihe
Finashin, Sergey
contents We analyse the action of the basic Dehn twists on the essential curves, $γ$, in a disc with 3 marked points, $\mathbb D_3$. In particular, we interpret the induced dynamics on the Dynnikov plane in terms of the standard dynamics in homology $H_1({\rm T})=\mathbb Z^2$ of the branched covering torus with a hole, ${\rm T}\to \mathbb D_3$. Our explicit description of orbits of the action of the pure mapping class group ${\rm PMod}(\mathbb D_3)$ can be viewed as a solution of the conjugacy problem for the Dehn twists $t_γ$. We also present an ``untwisting algorithm'' for factorization of this problem into a minimal number of steps.
format Preprint
id arxiv_https___arxiv_org_abs_2603_14582
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Recognising conjugacy classes of Dehn twists on $\mathbb D_3$
Atalan, Ferihe
Finashin, Sergey
Geometric Topology
57K20, 20F10, 37E30, 20E45, 05C12
We analyse the action of the basic Dehn twists on the essential curves, $γ$, in a disc with 3 marked points, $\mathbb D_3$. In particular, we interpret the induced dynamics on the Dynnikov plane in terms of the standard dynamics in homology $H_1({\rm T})=\mathbb Z^2$ of the branched covering torus with a hole, ${\rm T}\to \mathbb D_3$. Our explicit description of orbits of the action of the pure mapping class group ${\rm PMod}(\mathbb D_3)$ can be viewed as a solution of the conjugacy problem for the Dehn twists $t_γ$. We also present an ``untwisting algorithm'' for factorization of this problem into a minimal number of steps.
title Recognising conjugacy classes of Dehn twists on $\mathbb D_3$
topic Geometric Topology
57K20, 20F10, 37E30, 20E45, 05C12
url https://arxiv.org/abs/2603.14582