{
  "id": "math/0504328",
  "version": "v2",
  "published": "2005-04-15T17:16:34.000Z",
  "updated": "2005-04-21T08:15:13.000Z",
  "title": "Curve complexes and finite index subgroups of mapping class groups",
  "authors": [
    "Jason Behrstock",
    "Dan Margalit"
  ],
  "comment": "17 pages, 1 figure, minor mistake in closed genus 2 case corrected, references updated",
  "journal": "Geometriae Dedicata, 118, (2006), 71-85",
  "categories": [
    "math.GT",
    "math.GR"
  ],
  "abstract": "Let Mod(S) be the extended mapping class group of a surface S. For S the twice-punctured torus, we show that there exists an isomorphism of finite index subgroups of Mod(S) which is not the restriction of an inner automorphism. For S a torus with at least three punctures, we show that every injection of a finite index subgroup of Mod(S) into Mod(S) is the restriction of an inner automorphism; this completes a program begun by Irmak. For all of the above surfaces, we establish the co-Hopf property for finite index subgroups of Mod(S).",
  "revisions": [
    {
      "version": "v2",
      "updated": "2005-04-21T08:15:13.000Z"
    }
  ],
  "analyses": {
    "subjects": [
      "57M99",
      "20F38"
    ],
    "keywords": [
      "finite index subgroup",
      "curve complexes",
      "inner automorphism",
      "restriction",
      "extended mapping class group"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 17,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2005math......4328B"
    }
  }
}