{ "id": "2307.13970", "version": "v1", "published": "2023-07-26T06:10:25.000Z", "updated": "2023-07-26T06:10:25.000Z", "title": "Groups generated by Dehn Twists along fillings of surfaces", "authors": [ "Rakesh Kumar" ], "categories": [ "math.GT" ], "abstract": "Let $S_g$ denote a closed oriented surface of genus $g \\geq 2$. A set $\\Omega = \\{ c_1, \\dots, c_d\\}$ of pairwise non-homotopic simple closed curves on $S_g$ is called a filling system or simply a filling of $S_g$, if $S_g\\setminus \\Omega$ is a union of $\\ell$ topological discs for some $\\ell\\geq 1$. For $1\\leq i\\leq d$, let $T_{c_i}$ denotes the Dehn twist along $c_i$. In this article, we show that for each $d\\geq 2$, there exists a filling $\\Omega=\\{c_1,c_2,\\dots, c_d\\}$ of $S_g$ such that the group $\\langle T_{c_1}, T_{c_2},\\dots,T_{c_d}\\rangle$ is isomorphic to the free group of rank $d$.", "revisions": [ { "version": "v1", "updated": "2023-07-26T06:10:25.000Z" } ], "analyses": { "subjects": [ "57K20", "57M15", "05C10" ], "keywords": [ "dehn twist", "pairwise non-homotopic simple closed curves", "free group", "filling system", "oriented surface" ], "note": { "typesetting": "TeX", "pages": 0, "language": "en", "license": "arXiv", "status": "editable" } } }